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Diffstat (limited to 'third_party/webrender/swgl/src/rasterize.h')
| -rw-r--r-- | third_party/webrender/swgl/src/rasterize.h | 1670 |
1 files changed, 0 insertions, 1670 deletions
diff --git a/third_party/webrender/swgl/src/rasterize.h b/third_party/webrender/swgl/src/rasterize.h deleted file mode 100644 index 48f3b9e5898..00000000000 --- a/third_party/webrender/swgl/src/rasterize.h +++ /dev/null @@ -1,1670 +0,0 @@ -/* This Source Code Form is subject to the terms of the Mozilla Public - * License, v. 2.0. If a copy of the MPL was not distributed with this - * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ - -// The SWGL depth buffer is roughly organized as a span buffer where each row -// of the depth buffer is a list of spans, and each span has a constant depth -// and a run length (represented by DepthRun). The span from start..start+count -// is placed directly at that start index in the row's array of runs, so that -// there is no need to explicitly record the start index at all. This also -// avoids the need to move items around in the run array to manage insertions -// since space is implicitly always available for a run between any two -// pre-existing runs. Linkage from one run to the next is implicitly defined by -// the count, so if a run exists from start..start+count, the next run will -// implicitly pick up right at index start+count where that preceding run left -// off. All of the DepthRun items that are after the head of the run can remain -// uninitialized until the run needs to be split and a new run needs to start -// somewhere in between. -// For uses like perspective-correct rasterization or with a discard mask, a -// run is not an efficient representation, and it is more beneficial to have -// a flattened array of individual depth samples that can be masked off easily. -// To support this case, the first run in a given row's run array may have a -// zero count, signaling that this entire row is flattened. Critically, the -// depth and count fields in DepthRun are ordered (endian-dependently) so that -// the DepthRun struct can be interpreted as a sign-extended int32_t depth. It -// is then possible to just treat the entire row as an array of int32_t depth -// samples that can be processed with SIMD comparisons, since the count field -// behaves as just the sign-extension of the depth field. The count field is -// limited to 8 bits so that we can support depth values up to 24 bits. -// When a depth buffer is cleared, each row is initialized to a maximal runs -// spanning the entire row. In the normal case, the depth buffer will continue -// to manage itself as a list of runs. If perspective or discard is used for -// a given row, the row will be converted to the flattened representation to -// support it, after which it will only ever revert back to runs if the depth -// buffer is cleared. - -// The largest 24-bit depth value supported. -constexpr uint32_t MAX_DEPTH_VALUE = 0xFFFFFF; -// The longest 8-bit depth run that is supported, aligned to SIMD chunk size. -constexpr uint32_t MAX_DEPTH_RUN = 255 & ~3; - -struct DepthRun { - // Ensure that depth always occupies the LSB and count the MSB so that we - // can sign-extend depth just by setting count to zero, marking it flat. - // When count is non-zero, then this is interpreted as an actual run and - // depth is read in isolation. -#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__ - uint32_t depth : 24; - uint32_t count : 8; -#else - uint32_t count : 8; - uint32_t depth : 24; -#endif - - DepthRun() = default; - DepthRun(uint32_t depth, uint8_t count) : depth(depth), count(count) {} - - // If count is zero, this is actually a flat depth sample rather than a run. - bool is_flat() const { return !count; } - - // Compare a source depth from rasterization with a stored depth value. - template <int FUNC> - ALWAYS_INLINE bool compare(uint32_t src) const { - switch (FUNC) { - case GL_LEQUAL: - return src <= depth; - case GL_LESS: - return src < depth; - case GL_ALWAYS: - return true; - default: - assert(false); - return false; - } - } -}; - -// Fills runs at the given position with the given depth up to the span width. -static ALWAYS_INLINE void set_depth_runs(DepthRun* runs, uint32_t depth, - uint32_t width) { - // If the width exceeds the maximum run size, then we need to output clamped - // runs first. - for (; width >= MAX_DEPTH_RUN; - runs += MAX_DEPTH_RUN, width -= MAX_DEPTH_RUN) { - *runs = DepthRun(depth, MAX_DEPTH_RUN); - } - // If there are still any left over samples to fill under the maximum run - // size, then output one last run for them. - if (width > 0) { - *runs = DepthRun(depth, width); - } -} - -// A cursor for reading and modifying a row's depth run array. It locates -// and iterates through a desired span within all the runs, testing if -// the depth of this span passes or fails the depth test against existing -// runs. If desired, new runs may be inserted to represent depth occlusion -// from this span in the run array. -struct DepthCursor { - // Current position of run the cursor has advanced to. - DepthRun* cur = nullptr; - // The start of the remaining potential samples in the desired span. - DepthRun* start = nullptr; - // The end of the potential samples in the desired span. - DepthRun* end = nullptr; - - DepthCursor() = default; - - // Construct a cursor with runs for a given row's run array and the bounds - // of the span we wish to iterate within it. - DepthCursor(DepthRun* runs, int num_runs, int span_offset, int span_count) - : cur(runs), start(&runs[span_offset]), end(start + span_count) { - // This cursor should never iterate over flat runs - assert(!runs->is_flat()); - DepthRun* end_runs = &runs[num_runs]; - // Clamp end of span to end of row - if (end > end_runs) { - end = end_runs; - } - // If the span starts past the end of the row, just advance immediately - // to it to signal that we're done. - if (start >= end_runs) { - cur = end_runs; - start = end_runs; - return; - } - // Otherwise, find the first depth run that contains the start of the span. - // If the span starts after the given run, then we need to keep searching - // through the row to find an appropriate run. The check above already - // guaranteed that the span starts within the row's runs, and the search - // won't fall off the end. - for (;;) { - assert(cur < end); - DepthRun* next = cur + cur->count; - if (start < next) { - break; - } - cur = next; - } - } - - // The cursor is valid if the current position is at the end or if the run - // contains the start position. - bool valid() const { - return cur >= end || (cur <= start && start < cur + cur->count); - } - - // Skip past any initial runs that fail the depth test. If we find a run that - // would pass, then return the accumulated length between where we started - // and that position. Otherwise, if we fall off the end, return -1 to signal - // that there are no more passed runs at the end of this failed region and - // so it is safe for the caller to stop processing any more regions in this - // row. - template <int FUNC> - int skip_failed(uint32_t val) { - assert(valid()); - DepthRun* prev = start; - while (cur < end) { - if (cur->compare<FUNC>(val)) { - return start - prev; - } - cur += cur->count; - start = cur; - } - return -1; - } - - // Helper to convert function parameters into template parameters to hoist - // some checks out of inner loops. - ALWAYS_INLINE int skip_failed(uint32_t val, GLenum func) { - switch (func) { - case GL_LEQUAL: - return skip_failed<GL_LEQUAL>(val); - case GL_LESS: - return skip_failed<GL_LESS>(val); - default: - assert(false); - return -1; - } - } - - // Find a region of runs that passes the depth test. It is assumed the caller - // has called skip_failed first to skip past any runs that failed the depth - // test. This stops when it finds a run that fails the depth test or we fall - // off the end of the row. If the write mask is enabled, this will insert runs - // to represent this new region that passed the depth test. The length of the - // region is returned. - template <int FUNC, bool MASK> - int check_passed(uint32_t val) { - assert(valid()); - DepthRun* prev = cur; - while (cur < end) { - if (!cur->compare<FUNC>(val)) { - break; - } - DepthRun* next = cur + cur->count; - if (next > end) { - if (MASK) { - // Chop the current run where the end of the span falls, making a new - // run from the end of the span till the next run. The beginning of - // the current run will be folded into the run from the start of the - // passed region before returning below. - *end = DepthRun(cur->depth, next - end); - } - // If the next run starts past the end, then just advance the current - // run to the end to signal that we're now at the end of the row. - next = end; - } - cur = next; - } - // If we haven't advanced past the start of the span region, then we found - // nothing that passed. - if (cur <= start) { - return 0; - } - // If 'end' fell within the middle of a passing run, then 'cur' will end up - // pointing at the new partial run created at 'end' where the passing run - // was split to accommodate starting in the middle. The preceding runs will - // be fixed below to properly join with this new split. - int passed = cur - start; - if (MASK) { - // If the search started from a run before the start of the span, then - // edit that run to meet up with the start. - if (prev < start) { - prev->count = start - prev; - } - // Create a new run for the entirety of the passed samples. - set_depth_runs(start, val, passed); - } - start = cur; - return passed; - } - - // Helper to convert function parameters into template parameters to hoist - // some checks out of inner loops. - template <bool MASK> - ALWAYS_INLINE int check_passed(uint32_t val, GLenum func) { - switch (func) { - case GL_LEQUAL: - return check_passed<GL_LEQUAL, MASK>(val); - case GL_LESS: - return check_passed<GL_LESS, MASK>(val); - default: - assert(false); - return 0; - } - } - - ALWAYS_INLINE int check_passed(uint32_t val, GLenum func, bool mask) { - return mask ? check_passed<true>(val, func) - : check_passed<false>(val, func); - } - - // Fill a region of runs with a given depth value, bypassing any depth test. - ALWAYS_INLINE void fill(uint32_t depth) { - check_passed<GL_ALWAYS, true>(depth); - } -}; - -// Initialize a depth texture by setting the first run in each row to encompass -// the entire row. -void Texture::init_depth_runs(uint32_t depth) { - if (!buf) return; - DepthRun* runs = (DepthRun*)buf; - for (int y = 0; y < height; y++) { - set_depth_runs(runs, depth, width); - runs += stride() / sizeof(DepthRun); - } - set_cleared(true); -} - -// Fill a portion of the run array with flattened depth samples. -static ALWAYS_INLINE void fill_flat_depth(DepthRun* dst, size_t n, - uint32_t depth) { - fill_n((uint32_t*)dst, n, depth); -} - -// Fills a scissored region of a depth texture with a given depth. -void Texture::fill_depth_runs(uint32_t depth, const IntRect& scissor) { - if (!buf) return; - assert(cleared()); - IntRect bb = bounds().intersection(scissor - offset); - DepthRun* runs = (DepthRun*)sample_ptr(0, bb.y0); - for (int rows = bb.height(); rows > 0; rows--) { - if (bb.width() >= width) { - // If the scissor region encompasses the entire row, reset the row to a - // single run encompassing the entire row. - set_depth_runs(runs, depth, width); - } else if (runs->is_flat()) { - // If the row is flattened, just directly fill the portion of the row. - fill_flat_depth(&runs[bb.x0], bb.width(), depth); - } else { - // Otherwise, if we are still using runs, then set up a cursor to fill - // it with depth runs. - DepthCursor(runs, width, bb.x0, bb.width()).fill(depth); - } - runs += stride() / sizeof(DepthRun); - } -} - -using ZMask = I32; - -#if USE_SSE2 -# define ZMASK_NONE_PASSED 0xFFFF -# define ZMASK_ALL_PASSED 0 -static inline uint32_t zmask_code(ZMask mask) { - return _mm_movemask_epi8(mask); -} -#else -# define ZMASK_NONE_PASSED 0xFFFFFFFFU -# define ZMASK_ALL_PASSED 0 -static inline uint32_t zmask_code(ZMask mask) { - return bit_cast<uint32_t>(CONVERT(mask, U8)); -} -#endif - -// Interprets items in the depth buffer as sign-extended 32-bit depth values -// instead of as runs. Returns a mask that signals which samples in the given -// chunk passed or failed the depth test with given Z value. -template <bool DISCARD> -static ALWAYS_INLINE bool check_depth(I32 src, DepthRun* zbuf, ZMask& outmask, - int span = 4) { - // SSE2 does not support unsigned comparison. So ensure Z value is - // sign-extended to int32_t. - I32 dest = unaligned_load<I32>(zbuf); - // Invert the depth test to check which pixels failed and should be discarded. - ZMask mask = ctx->depthfunc == GL_LEQUAL - ? - // GL_LEQUAL: Not(LessEqual) = Greater - ZMask(src > dest) - : - // GL_LESS: Not(Less) = GreaterEqual - ZMask(src >= dest); - // Mask off any unused lanes in the span. - mask |= ZMask(span) < ZMask{1, 2, 3, 4}; - if (zmask_code(mask) == ZMASK_NONE_PASSED) { - return false; - } - if (!DISCARD && ctx->depthmask) { - unaligned_store(zbuf, (mask & dest) | (~mask & src)); - } - outmask = mask; - return true; -} - -static ALWAYS_INLINE I32 packDepth() { - return cast(fragment_shader->gl_FragCoord.z * MAX_DEPTH_VALUE); -} - -static ALWAYS_INLINE void discard_depth(I32 src, DepthRun* zbuf, I32 mask) { - if (ctx->depthmask) { - I32 dest = unaligned_load<I32>(zbuf); - mask |= fragment_shader->swgl_IsPixelDiscarded; - unaligned_store(zbuf, (mask & dest) | (~mask & src)); - } -} - -static ALWAYS_INLINE void mask_output(uint32_t* buf, ZMask zmask, - int span = 4) { - WideRGBA8 r = pack_pixels_RGBA8(); - PackedRGBA8 dst = load_span<PackedRGBA8>(buf, span); - if (blend_key) r = blend_pixels(buf, dst, r, span); - PackedRGBA8 mask = bit_cast<PackedRGBA8>(zmask); - store_span(buf, (mask & dst) | (~mask & pack(r)), span); -} - -template <bool DISCARD> -static ALWAYS_INLINE void discard_output(uint32_t* buf, int span = 4) { - mask_output(buf, fragment_shader->swgl_IsPixelDiscarded, span); -} - -template <> -ALWAYS_INLINE void discard_output<false>(uint32_t* buf, int span) { - WideRGBA8 r = pack_pixels_RGBA8(); - if (blend_key) - r = blend_pixels(buf, load_span<PackedRGBA8>(buf, span), r, span); - store_span(buf, pack(r), span); -} - -static ALWAYS_INLINE void mask_output(uint8_t* buf, ZMask zmask, int span = 4) { - WideR8 r = pack_pixels_R8(); - WideR8 dst = unpack(load_span<PackedR8>(buf, span)); - if (blend_key) r = blend_pixels(buf, dst, r, span); - WideR8 mask = packR8(zmask); - store_span(buf, pack((mask & dst) | (~mask & r)), span); -} - -template <bool DISCARD> -static ALWAYS_INLINE void discard_output(uint8_t* buf, int span = 4) { - mask_output(buf, fragment_shader->swgl_IsPixelDiscarded, span); -} - -template <> -ALWAYS_INLINE void discard_output<false>(uint8_t* buf, int span) { - WideR8 r = pack_pixels_R8(); - if (blend_key) - r = blend_pixels(buf, unpack(load_span<PackedR8>(buf, span)), r, span); - store_span(buf, pack(r), span); -} - -struct ClipRect { - float x0; - float y0; - float x1; - float y1; - - explicit ClipRect(const IntRect& i) - : x0(i.x0), y0(i.y0), x1(i.x1), y1(i.y1) {} - explicit ClipRect(const Texture& t) : ClipRect(ctx->apply_scissor(t)) { - // If blending is enabled, set blend_key to reflect the resolved blend - // state for the currently drawn primitive. - if (ctx->blend) { - blend_key = ctx->blend_key; - if (swgl_ClipFlags) { - // If there is a blend override set, replace the blend key with it. - if (swgl_ClipFlags & SWGL_CLIP_FLAG_BLEND_OVERRIDE) { - blend_key = swgl_BlendOverride; - } - // If a clip mask is available, set up blending state to use the clip - // mask. - if (swgl_ClipFlags & SWGL_CLIP_FLAG_MASK) { - assert(swgl_ClipMask->format == TextureFormat::R8); - // Constrain the clip mask bounds to always fall within the clip mask. - swgl_ClipMaskBounds.intersect(IntRect{0, 0, int(swgl_ClipMask->width), - int(swgl_ClipMask->height)}); - // The clip mask offset is relative to the viewport. - swgl_ClipMaskOffset += ctx->viewport.origin() - t.offset; - // The clip mask bounds are relative to the clip mask offset. - swgl_ClipMaskBounds.offset(swgl_ClipMaskOffset); - // Finally, constrain the clip rectangle by the clip mask bounds. - intersect(swgl_ClipMaskBounds); - // Modify the blend key so that it will use the clip mask while - // blending. - restore_clip_mask(); - } - if (swgl_ClipFlags & SWGL_CLIP_FLAG_AA) { - // Modify the blend key so that it will use AA while blending. - restore_aa(); - } - } - } else { - blend_key = BLEND_KEY_NONE; - swgl_ClipFlags = 0; - } - } - - FloatRange x_range() const { return {x0, x1}; } - - void intersect(const IntRect& c) { - x0 = max(x0, float(c.x0)); - y0 = max(y0, float(c.y0)); - x1 = min(x1, float(c.x1)); - y1 = min(y1, float(c.y1)); - } - - template <typename P> - void set_clip_mask(int x, int y, P* buf) const { - if (swgl_ClipFlags & SWGL_CLIP_FLAG_MASK) { - swgl_SpanBuf = buf; - swgl_ClipMaskBuf = (uint8_t*)swgl_ClipMask->buf + - (y - swgl_ClipMaskOffset.y) * swgl_ClipMask->stride + - (x - swgl_ClipMaskOffset.x); - } - } - - template <typename P> - bool overlaps(int nump, const P* p) const { - // Generate a mask of which side of the clip rect all of a polygon's points - // fall inside of. This is a cheap conservative estimate of whether the - // bounding box of the polygon might overlap the clip rect, rather than an - // exact test that would require multiple slower line intersections. - int sides = 0; - for (int i = 0; i < nump; i++) { - sides |= p[i].x < x1 ? (p[i].x > x0 ? 1 | 2 : 1) : 2; - sides |= p[i].y < y1 ? (p[i].y > y0 ? 4 | 8 : 4) : 8; - } - return sides == 0xF; - } -}; - -// Given a current X position at the center Y position of a row, return the X -// position of the left and right intercepts of the row top and bottom. -template <typename E> -static ALWAYS_INLINE FloatRange x_intercepts(const E& e) { - float rad = 0.5f * abs(e.x_slope()); - return {e.cur_x() - rad, e.cur_x() + rad}; -} - -// Return the AA sub-span corresponding to a given edge. If AA is requested, -// then this finds the X intercepts with the row clipped into range of the -// edge and finally conservatively rounds them out. If there is no AA, then -// it just returns the current rounded X position clipped within bounds. -template <typename E> -static ALWAYS_INLINE IntRange aa_edge(const E& e, const FloatRange& bounds) { - return e.edgeMask ? bounds.clip(x_intercepts(e)).round_out() - : bounds.clip({e.cur_x(), e.cur_x()}).round(); -} - -// Calculate the initial AA coverage as an approximation of the distance from -// the center of the pixel in the direction of the edge slope. Given an edge -// (x,y)..(x+dx,y+dy), then the normalized tangent vector along the edge is -// (dx,dy)/sqrt(dx^2+dy^2). We know that for dy=1 then dx=e.x_slope. We rotate -// the tangent vector either -90 or +90 degrees to get the edge normal vector, -// where 'dx=-dy and 'dy=dx. Once normalized by 1/sqrt(dx^2+dy^2), scale into -// the range of 0..256 so that we can cheaply convert to a fixed-point scale -// factor. It is assumed that at exactly the pixel center the opacity is half -// (128) and linearly decreases along the normal vector at 1:1 scale with the -// slope. While not entirely accurate, this gives a reasonably agreeable looking -// approximation of AA. For edges on which there is no AA, just force the -// opacity to maximum (256) with no slope, relying on the span clipping to trim -// pixels outside the span. -template <typename E> -static ALWAYS_INLINE FloatRange aa_dist(const E& e, float dir) { - if (e.edgeMask) { - float dx = (dir * 256.0f) * inversesqrt(1.0f + e.x_slope() * e.x_slope()); - return {128.0f + dx * (e.cur_x() - 0.5f), -dx}; - } else { - return {256.0f, 0.0f}; - } -} - -template <typename P, typename E> -static ALWAYS_INLINE IntRange aa_span(P* buf, const E& left, const E& right, - const FloatRange& bounds) { - // If there is no AA, just return the span from the rounded left edge X - // position to the rounded right edge X position. Clip the span to be within - // the valid bounds. - if (!(swgl_ClipFlags & SWGL_CLIP_FLAG_AA)) { - return bounds.clip({left.cur_x(), right.cur_x()}).round(); - } - - // Calculate the left and right AA spans along with the coverage distances - // and slopes necessary to do blending. - IntRange leftAA = aa_edge(left, bounds); - FloatRange leftDist = aa_dist(left, -1.0f); - IntRange rightAA = aa_edge(right, bounds); - FloatRange rightDist = aa_dist(right, 1.0f); - - // Use the pointer into the destination buffer as a status indicator of the - // coverage offset. The pointer is calculated so that subtracting it with - // the current destination pointer will yield a negative value if the span - // is outside the opaque area and otherwise will yield a positive value - // above the opaque size. This pointer is stored as a uint8 pointer so that - // there are no hidden multiplication instructions and will just return a - // 1:1 linear memory address. Thus the size of the opaque region must also - // be scaled by the pixel size in bytes. - swgl_OpaqueStart = (const uint8_t*)(buf + leftAA.end); - swgl_OpaqueSize = max(rightAA.start - leftAA.end - 3, 0) * sizeof(P); - - // Offset the coverage distances by the end of the left AA span, which - // corresponds to the opaque start pointer, so that pixels become opaque - // immediately after. The distances are also offset for each lane in the - // chunk. - Float offset = cast(leftAA.end + (I32){0, 1, 2, 3}); - swgl_LeftAADist = leftDist.start + offset * leftDist.end; - swgl_RightAADist = rightDist.start + offset * rightDist.end; - swgl_AASlope = - (Float){leftDist.end, rightDist.end, 0.0f, 0.0f} / float(sizeof(P)); - - // Return the full span width from the start of the left span to the end of - // the right span. - return {leftAA.start, rightAA.end}; -} - -// Calculate the span the user clip distances occupy from the left and right -// edges at the current row. -template <typename E> -static ALWAYS_INLINE IntRange clip_distance_range(const E& left, - const E& right) { - Float leftClip = get_clip_distances(left.interp); - Float rightClip = get_clip_distances(right.interp); - // Get the change in clip dist per X step. - Float clipStep = (rightClip - leftClip) / (right.cur_x() - left.cur_x()); - // Find the zero intercepts starting from the left edge. - Float clipDist = left.cur_x() - leftClip * recip(clipStep); - // Find the distance to the start of the span for any clip distances that - // are increasing in value. If the clip distance is constant or decreasing - // in value, then check if it starts outside the clip volume. - Float start = if_then_else(clipStep > 0.0f, clipDist, - if_then_else(leftClip < 0.0f, 1.0e6f, 0.0f)); - // Find the distance to the end of the span for any clip distances that are - // decreasing in value. If the clip distance is constant or increasing in - // value, then check if it ends inside the clip volume. - Float end = if_then_else(clipStep < 0.0f, clipDist, - if_then_else(rightClip >= 0.0f, 1.0e6f, 0.0f)); - // Find the furthest start offset. - start = max(start, start.zwxy); - // Find the closest end offset. - end = min(end, end.zwxy); - // Finally, round the offsets to an integer span that can be used to bound - // the current span. - return FloatRange{max(start.x, start.y), min(end.x, end.y)}.round(); -} - -// Converts a run array into a flattened array of depth samples. This just -// walks through every run and fills the samples with the depth value from -// the run. -static void flatten_depth_runs(DepthRun* runs, size_t width) { - if (runs->is_flat()) { - return; - } - while (width > 0) { - size_t n = runs->count; - fill_flat_depth(runs, n, runs->depth); - runs += n; - width -= n; - } -} - -// Helper function for drawing passed depth runs within the depth buffer. -// Flattened depth (perspective or discard) is not supported. -template <typename P> -static ALWAYS_INLINE void draw_depth_span(uint32_t z, P* buf, - DepthCursor& cursor) { - for (;;) { - // Get the span that passes the depth test. Assume on entry that - // any failed runs have already been skipped. - int span = cursor.check_passed(z, ctx->depthfunc, ctx->depthmask); - // If nothing passed, since we already skipped passed failed runs - // previously, we must have hit the end of the row. Bail out. - if (span <= 0) { - break; - } - if (span >= 4) { - // If we have a draw specialization, try to process as many 4-pixel - // chunks as possible using it. - if (fragment_shader->has_draw_span(buf)) { - int drawn = fragment_shader->draw_span(buf, span & ~3); - buf += drawn; - span -= drawn; - } - // Otherwise, just process each chunk individually. - while (span >= 4) { - fragment_shader->run(); - discard_output<false>(buf); - buf += 4; - span -= 4; - } - } - // If we have a partial chunk left over, we still have to process it as if - // it were a full chunk. Mask off only the part of the chunk we want to - // use. - if (span > 0) { - fragment_shader->run(); - discard_output<false>(buf, span); - buf += span; - } - // Skip past any runs that fail the depth test. - int skip = cursor.skip_failed(z, ctx->depthfunc); - // If there aren't any, that means we won't encounter any more passing runs - // and so it's safe to bail out. - if (skip <= 0) { - break; - } - // Advance interpolants for the fragment shader past the skipped region. - // If we processed a partial chunk above, we actually advanced the - // interpolants a full chunk in the fragment shader's run function. Thus, - // we need to first subtract off that 4-pixel chunk and only partially - // advance them to that partial chunk before we can add on the rest of the - // skips. This is combined with the skip here for efficiency's sake. - fragment_shader->skip(skip - (span > 0 ? 4 - span : 0)); - buf += skip; - } -} - -// Draw a simple span in 4-pixel wide chunks, optionally using depth. -template <bool DISCARD, bool W, typename P, typename Z> -static ALWAYS_INLINE void draw_span(P* buf, DepthRun* depth, int span, Z z) { - if (depth) { - // Depth testing is enabled. If perspective is used, Z values will vary - // across the span, we use packDepth to generate packed Z values suitable - // for depth testing based on current values from gl_FragCoord.z. - // Otherwise, for the no-perspective case, we just use the provided Z. - // Process 4-pixel chunks first. - for (; span >= 4; span -= 4, buf += 4, depth += 4) { - I32 zsrc = z(); - ZMask zmask; - if (check_depth<DISCARD>(zsrc, depth, zmask)) { - fragment_shader->run<W>(); - mask_output(buf, zmask); - if (DISCARD) discard_depth(zsrc, depth, zmask); - } else { - fragment_shader->skip<W>(); - } - } - // If there are any remaining pixels, do a partial chunk. - if (span > 0) { - I32 zsrc = z(); - ZMask zmask; - if (check_depth<DISCARD>(zsrc, depth, zmask, span)) { - fragment_shader->run<W>(); - mask_output(buf, zmask, span); - if (DISCARD) discard_depth(zsrc, depth, zmask); - } - } - } else { - // Process 4-pixel chunks first. - for (; span >= 4; span -= 4, buf += 4) { - fragment_shader->run<W>(); - discard_output<DISCARD>(buf); - } - // If there are any remaining pixels, do a partial chunk. - if (span > 0) { - fragment_shader->run<W>(); - discard_output<DISCARD>(buf, span); - } - } -} - -// Called during rasterization to forcefully clear a row on which delayed clear -// has been enabled. If we know that we are going to completely overwrite a part -// of the row, then we only need to clear the row outside of that part. However, -// if blending or discard is enabled, the values of that underlying part of the -// row may be used regardless to produce the final rasterization result, so we -// have to then clear the entire underlying row to prepare it. -template <typename P> -static inline void prepare_row(Texture& colortex, int y, int startx, int endx, - bool use_discard, DepthRun* depth, - uint32_t z = 0, DepthCursor* cursor = nullptr) { - assert(colortex.delay_clear > 0); - // Delayed clear is enabled for the color buffer. Check if needs clear. - uint32_t& mask = colortex.cleared_rows[y / 32]; - if ((mask & (1 << (y & 31))) == 0) { - mask |= 1 << (y & 31); - colortex.delay_clear--; - if (blend_key || use_discard) { - // If depth test, blending, or discard is used, old color values - // might be sampled, so we need to clear the entire row to fill it. - force_clear_row<P>(colortex, y); - } else if (depth) { - if (depth->is_flat() || !cursor) { - // If flat depth is used, we can't cheaply predict if which samples will - // pass. - force_clear_row<P>(colortex, y); - } else { - // Otherwise if depth runs are used, see how many samples initially pass - // the depth test and only fill the row outside those. The fragment - // shader will fill the row within the passed samples. - int passed = - DepthCursor(*cursor).check_passed<false>(z, ctx->depthfunc); - if (startx > 0 || startx + passed < colortex.width) { - force_clear_row<P>(colortex, y, startx, startx + passed); - } - } - } else if (startx > 0 || endx < colortex.width) { - // Otherwise, we only need to clear the row outside of the span. - // The fragment shader will fill the row within the span itself. - force_clear_row<P>(colortex, y, startx, endx); - } - } -} - -// Perpendicular dot-product is the dot-product of a vector with the -// perpendicular vector of the other, i.e. dot(a, {-b.y, b.x}) -template <typename T> -static ALWAYS_INLINE auto perpDot(T a, T b) { - return a.x * b.y - a.y * b.x; -} - -// Check if the winding of the initial edges is flipped, requiring us to swap -// the edges to avoid spans having negative lengths. Assume that l0.y == r0.y -// due to the initial edge scan in draw_quad/perspective_spans. -template <typename T> -static ALWAYS_INLINE bool checkIfEdgesFlipped(T l0, T l1, T r0, T r1) { - // If the starting point of the left edge is to the right of the starting - // point of the right edge, then just assume the edges are flipped. If the - // left and right starting points are the same, then check the sign of the - // cross-product of the edges to see if the edges are flipped. Otherwise, - // if the left starting point is actually just to the left of the right - // starting point, then assume no edge flip. - return l0.x > r0.x || (l0.x == r0.x && perpDot(l1 - l0, r1 - r0) > 0.0f); -} - -// Draw spans for each row of a given quad (or triangle) with a constant Z -// value. The quad is assumed convex. It is clipped to fall within the given -// clip rect. In short, this function rasterizes a quad by first finding a -// top most starting point and then from there tracing down the left and right -// sides of this quad until it hits the bottom, outputting a span between the -// current left and right positions at each row along the way. Points are -// assumed to be ordered in either CW or CCW to support this, but currently -// both orders (CW and CCW) are supported and equivalent. -template <typename P> -static inline void draw_quad_spans(int nump, Point2D p[4], uint32_t z, - Interpolants interp_outs[4], - Texture& colortex, Texture& depthtex, - const ClipRect& clipRect) { - // Only triangles and convex quads supported. - assert(nump == 3 || nump == 4); - - Point2D l0, r0, l1, r1; - int l0i, r0i, l1i, r1i; - { - // Find the index of the top-most (smallest Y) point from which - // rasterization can start. - int top = nump > 3 && p[3].y < p[2].y - ? (p[0].y < p[1].y ? (p[0].y < p[3].y ? 0 : 3) - : (p[1].y < p[3].y ? 1 : 3)) - : (p[0].y < p[1].y ? (p[0].y < p[2].y ? 0 : 2) - : (p[1].y < p[2].y ? 1 : 2)); - // Helper to find next index in the points array, walking forward. -#define NEXT_POINT(idx) \ - ({ \ - int cur = (idx) + 1; \ - cur < nump ? cur : 0; \ - }) - // Helper to find the previous index in the points array, walking backward. -#define PREV_POINT(idx) \ - ({ \ - int cur = (idx)-1; \ - cur >= 0 ? cur : nump - 1; \ - }) - // Start looking for "left"-side and "right"-side descending edges starting - // from the determined top point. - int next = NEXT_POINT(top); - int prev = PREV_POINT(top); - if (p[top].y == p[next].y) { - // If the next point is on the same row as the top, then advance one more - // time to the next point and use that as the "left" descending edge. - l0i = next; - l1i = NEXT_POINT(next); - // Assume top and prev form a descending "right" edge, as otherwise this - // will be a collapsed polygon and harmlessly bail out down below. - r0i = top; - r1i = prev; - } else if (p[top].y == p[prev].y) { - // If the prev point is on the same row as the top, then advance to the - // prev again and use that as the "right" descending edge. - // Assume top and next form a non-empty descending "left" edge. - l0i = top; - l1i = next; - r0i = prev; - r1i = PREV_POINT(prev); - } else { - // Both next and prev are on distinct rows from top, so both "left" and - // "right" edges are non-empty/descending. - l0i = r0i = top; - l1i = next; - r1i = prev; - } - // Load the points from the indices. - l0 = p[l0i]; // Start of left edge - r0 = p[r0i]; // End of left edge - l1 = p[l1i]; // Start of right edge - r1 = p[r1i]; // End of right edge - // debugf("l0: %d(%f,%f), r0: %d(%f,%f) -> l1: %d(%f,%f), r1: - // %d(%f,%f)\n", l0i, l0.x, l0.y, r0i, r0.x, r0.y, l1i, l1.x, l1.y, r1i, - // r1.x, r1.y); - } - - struct Edge { - float yScale; - float xSlope; - float x; - Interpolants interpSlope; - Interpolants interp; - bool edgeMask; - - Edge(float y, const Point2D& p0, const Point2D& p1, const Interpolants& i0, - const Interpolants& i1, int edgeIndex) - : // Inverse Y scale for slope calculations. Avoid divide on 0-length - // edge. Later checks below ensure that Y <= p1.y, or otherwise we - // don't use this edge. We just need to guard against Y == p1.y == - // p0.y. In that case, Y - p0.y == 0 and will cancel out the slopes - // below, except if yScale is Inf for some reason (or worse, NaN), - // which 1/(p1.y-p0.y) might produce if we don't bound it. - yScale(1.0f / max(p1.y - p0.y, 1.0f / 256)), - // Calculate dX/dY slope - xSlope((p1.x - p0.x) * yScale), - // Initialize current X based on Y and slope - x(p0.x + (y - p0.y) * xSlope), - // Calculate change in interpolants per change in Y - interpSlope((i1 - i0) * yScale), - // Initialize current interpolants based on Y and slope - interp(i0 + (y - p0.y) * interpSlope), - // Extract the edge mask status for this edge - edgeMask((swgl_AAEdgeMask >> edgeIndex) & 1) {} - - void nextRow() { - // step current X and interpolants to next row from slope - x += xSlope; - interp += interpSlope; - } - - float cur_x() const { return x; } - float x_slope() const { return xSlope; } - }; - - // Vertex selection above should result in equal left and right start rows - assert(l0.y == r0.y); - // Find the start y, clip to within the clip rect, and round to row center. - // If AA is enabled, round out conservatively rather than round to nearest. - float aaRound = swgl_ClipFlags & SWGL_CLIP_FLAG_AA ? 0.0f : 0.5f; - float y = floor(max(l0.y, clipRect.y0) + aaRound) + 0.5f; - // Initialize left and right edges from end points and start Y - Edge left(y, l0, l1, interp_outs[l0i], interp_outs[l1i], l1i); - Edge right(y, r0, r1, interp_outs[r0i], interp_outs[r1i], r0i); - // WR does not use backface culling, so check if edges are flipped. - bool flipped = checkIfEdgesFlipped(l0, l1, r0, r1); - if (flipped) swap(left, right); - // Get pointer to color buffer and depth buffer at current Y - P* fbuf = (P*)colortex.sample_ptr(0, int(y)); - DepthRun* fdepth = (DepthRun*)depthtex.sample_ptr(0, int(y)); - // Loop along advancing Ys, rasterizing spans at each row - float checkY = min(min(l1.y, r1.y), clipRect.y1); - // Ensure we don't rasterize out edge bounds - FloatRange clipSpan = - clipRect.x_range().clip(x_range(l0, l1).merge(x_range(r0, r1))); - for (;;) { - // Check if we maybe passed edge ends or outside clip rect... - if (y > checkY) { - // If we're outside the clip rect, we're done. - if (y > clipRect.y1) break; - // Helper to find the next non-duplicate vertex that doesn't loop back. -#define STEP_EDGE(y, e0i, e0, e1i, e1, STEP_POINT, end) \ - do { \ - /* Set new start of edge to be end of old edge */ \ - e0i = e1i; \ - e0 = e1; \ - /* Set new end of edge to next point */ \ - e1i = STEP_POINT(e1i); \ - e1 = p[e1i]; \ - /* If the edge crossed the end, we're done. */ \ - if (e0i == end) return; \ - /* Otherwise, it doesn't advance, so keep searching. */ \ - } while (y > e1.y) - // Check if Y advanced past the end of the left edge - if (y > l1.y) { - // Step to next left edge past Y and reset edge interpolants. - STEP_EDGE(y, l0i, l0, l1i, l1, NEXT_POINT, r1i); - (flipped ? right : left) = - Edge(y, l0, l1, interp_outs[l0i], interp_outs[l1i], l1i); - } - // Check if Y advanced past the end of the right edge - if (y > r1.y) { - // Step to next right edge past Y and reset edge interpolants. - STEP_EDGE(y, r0i, r0, r1i, r1, PREV_POINT, l1i); - (flipped ? left : right) = - Edge(y, r0, r1, interp_outs[r0i], interp_outs[r1i], r0i); - } - // Reset the clip bounds for the new edges - clipSpan = - clipRect.x_range().clip(x_range(l0, l1).merge(x_range(r0, r1))); - // Reset check condition for next time around. - checkY = min(ceil(min(l1.y, r1.y) - aaRound), clipRect.y1); - } - - // Calculate a potentially AA'd span and check if it is non-empty. - IntRange span = aa_span(fbuf, left, right, clipSpan); - if (span.len() > 0) { - // If user clip planes are enabled, use them to bound the current span. - if (vertex_shader->use_clip_distance()) { - span = span.intersect(clip_distance_range(left, right)); - if (span.len() <= 0) goto next_span; - } - ctx->shaded_rows++; - ctx->shaded_pixels += span.len(); - // Advance color/depth buffer pointers to the start of the span. - P* buf = fbuf + span.start; - // Check if we will need to use depth-buffer or discard on this span. - DepthRun* depth = - depthtex.buf != nullptr && depthtex.cleared() ? fdepth : nullptr; - DepthCursor cursor; - bool use_discard = fragment_shader->use_discard(); - if (use_discard) { - if (depth) { - // If we're using discard, we may have to unpredictably drop out some - // samples. Flatten the depth run array here to allow this. - if (!depth->is_flat()) { - flatten_depth_runs(depth, depthtex.width); - } - // Advance to the depth sample at the start of the span. - depth += span.start; - } - } else if (depth) { - if (!depth->is_flat()) { - // We're not using discard and the depth row is still organized into - // runs. Skip past any runs that would fail the depth test so we - // don't have to do any extra work to process them with the rest of - // the span. - cursor = DepthCursor(depth, depthtex.width, span.start, span.len()); - int skipped = cursor.skip_failed(z, ctx->depthfunc); - // If we fell off the row, that means we couldn't find any passing - // runs. We can just skip the entire span. - if (skipped < 0) { - goto next_span; - } - buf += skipped; - span.start += skipped; - } else { - // The row is already flattened, so just advance to the span start. - depth += span.start; - } - } - - if (colortex.delay_clear) { - // Delayed clear is enabled for the color buffer. Check if needs clear. - prepare_row<P>(colortex, int(y), span.start, span.end, use_discard, - depth, z, &cursor); - } - - // Initialize fragment shader interpolants to current span position. - fragment_shader->gl_FragCoord.x = init_interp(span.start + 0.5f, 1); - fragment_shader->gl_FragCoord.y = y; - { - // Change in interpolants is difference between current right and left - // edges per the change in right and left X. - Interpolants step = - (right.interp - left.interp) * (1.0f / (right.x - left.x)); - // Advance current interpolants to X at start of span. - Interpolants o = left.interp + step * (span.start + 0.5f - left.x); - fragment_shader->init_span(&o, &step); - } - clipRect.set_clip_mask(span.start, y, buf); - if (!use_discard) { - // Fast paths for the case where fragment discard is not used. - if (depth) { - // If depth is used, we want to process entire depth runs if depth is - // not flattened. - if (!depth->is_flat()) { - draw_depth_span(z, buf, cursor); - goto next_span; - } - // Otherwise, flattened depth must fall back to the slightly slower - // per-chunk depth test path in draw_span below. - } else { - // Check if the fragment shader has an optimized draw specialization. - if (span.len() >= 4 && fragment_shader->has_draw_span(buf)) { - // Draw specialization expects 4-pixel chunks. - int drawn = fragment_shader->draw_span(buf, span.len() & ~3); - buf += drawn; - span.start += drawn; - } - } - draw_span<false, false>(buf, depth, span.len(), [=] { return z; }); - } else { - // If discard is used, then use slower fallbacks. This should be rare. - // Just needs to work, doesn't need to be too fast yet... - draw_span<true, false>(buf, depth, span.len(), [=] { return z; }); - } - } - next_span: - // Advance Y and edge interpolants to next row. - y++; - left.nextRow(); - right.nextRow(); - // Advance buffers to next row. - fbuf += colortex.stride() / sizeof(P); - fdepth += depthtex.stride() / sizeof(DepthRun); - } -} - -// Draw perspective-correct spans for a convex quad that has been clipped to -// the near and far Z planes, possibly producing a clipped convex polygon with -// more than 4 sides. This assumes the Z value will vary across the spans and -// requires interpolants to factor in W values. This tends to be slower than -// the simpler 2D draw_quad_spans above, especially since we can't optimize the -// depth test easily when Z values, and should be used only rarely if possible. -template <typename P> -static inline void draw_perspective_spans(int nump, Point3D* p, - Interpolants* interp_outs, - Texture& colortex, Texture& depthtex, - const ClipRect& clipRect) { - Point3D l0, r0, l1, r1; - int l0i, r0i, l1i, r1i; - { - // Find the index of the top-most point (smallest Y) from which - // rasterization can start. - int top = 0; - for (int i = 1; i < nump; i++) { - if (p[i].y < p[top].y) { - top = i; - } - } - // Find left-most top point, the start of the left descending edge. - // Advance forward in the points array, searching at most nump points - // in case the polygon is flat. - l0i = top; - for (int i = top + 1; i < nump && p[i].y == p[top].y; i++) { - l0i = i; - } - if (l0i == nump - 1) { - for (int i = 0; i <= top && p[i].y == p[top].y; i++) { - l0i = i; - } - } - // Find right-most top point, the start of the right descending edge. - // Advance backward in the points array, searching at most nump points. - r0i = top; - for (int i = top - 1; i >= 0 && p[i].y == p[top].y; i--) { - r0i = i; - } - if (r0i == 0) { - for (int i = nump - 1; i >= top && p[i].y == p[top].y; i--) { - r0i = i; - } - } - // End of left edge is next point after left edge start. - l1i = NEXT_POINT(l0i); - // End of right edge is prev point after right edge start. - r1i = PREV_POINT(r0i); - l0 = p[l0i]; // Start of left edge - r0 = p[r0i]; // End of left edge - l1 = p[l1i]; // Start of right edge - r1 = p[r1i]; // End of right edge - } - - struct Edge { - float yScale; - // Current coordinates for edge. Where in the 2D case of draw_quad_spans, - // it is enough to just track the X coordinate as we advance along the rows, - // for the perspective case we also need to keep track of Z and W. For - // simplicity, we just use the full 3D point to track all these coordinates. - Point3D pSlope; - Point3D p; - Interpolants interpSlope; - Interpolants interp; - bool edgeMask; - - Edge(float y, const Point3D& p0, const Point3D& p1, const Interpolants& i0, - const Interpolants& i1, int edgeIndex) - : // Inverse Y scale for slope calculations. Avoid divide on 0-length - // edge. - yScale(1.0f / max(p1.y - p0.y, 1.0f / 256)), - // Calculate dX/dY slope - pSlope((p1 - p0) * yScale), - // Initialize current coords based on Y and slope - p(p0 + (y - p0.y) * pSlope), - // Crucially, these interpolants must be scaled by the point's 1/w - // value, which allows linear interpolation in a perspective-correct - // manner. This will be canceled out inside the fragment shader later. - // Calculate change in interpolants per change in Y - interpSlope((i1 * p1.w - i0 * p0.w) * yScale), - // Initialize current interpolants based on Y and slope - interp(i0 * p0.w + (y - p0.y) * interpSlope), - // Extract the edge mask status for this edge - edgeMask((swgl_AAEdgeMask >> edgeIndex) & 1) {} - - float x() const { return p.x; } - vec2_scalar zw() const { return {p.z, p.w}; } - - void nextRow() { - // step current coords and interpolants to next row from slope - p += pSlope; - interp += interpSlope; - } - - float cur_x() const { return p.x; } - float x_slope() const { return pSlope.x; } - }; - - // Vertex selection above should result in equal left and right start rows - assert(l0.y == r0.y); - // Find the start y, clip to within the clip rect, and round to row center. - // If AA is enabled, round out conservatively rather than round to nearest. - float aaRound = swgl_ClipFlags & SWGL_CLIP_FLAG_AA ? 0.0f : 0.5f; - float y = floor(max(l0.y, clipRect.y0) + aaRound) + 0.5f; - // Initialize left and right edges from end points and start Y - Edge left(y, l0, l1, interp_outs[l0i], interp_outs[l1i], l1i); - Edge right(y, r0, r1, interp_outs[r0i], interp_outs[r1i], r0i); - // WR does not use backface culling, so check if edges are flipped. - bool flipped = checkIfEdgesFlipped(l0, l1, r0, r1); - if (flipped) swap(left, right); - // Get pointer to color buffer and depth buffer at current Y - P* fbuf = (P*)colortex.sample_ptr(0, int(y)); - DepthRun* fdepth = (DepthRun*)depthtex.sample_ptr(0, int(y)); - // Loop along advancing Ys, rasterizing spans at each row - float checkY = min(min(l1.y, r1.y), clipRect.y1); - // Ensure we don't rasterize out edge bounds - FloatRange clipSpan = - clipRect.x_range().clip(x_range(l0, l1).merge(x_range(r0, r1))); - for (;;) { - // Check if we maybe passed edge ends or outside clip rect... - if (y > checkY) { - // If we're outside the clip rect, we're done. - if (y > clipRect.y1) break; - // Check if Y advanced past the end of the left edge - if (y > l1.y) { - // Step to next left edge past Y and reset edge interpolants. - STEP_EDGE(y, l0i, l0, l1i, l1, NEXT_POINT, r1i); - (flipped ? right : left) = - Edge(y, l0, l1, interp_outs[l0i], interp_outs[l1i], l1i); - } - // Check if Y advanced past the end of the right edge - if (y > r1.y) { - // Step to next right edge past Y and reset edge interpolants. - STEP_EDGE(y, r0i, r0, r1i, r1, PREV_POINT, l1i); - (flipped ? left : right) = - Edge(y, r0, r1, interp_outs[r0i], interp_outs[r1i], r0i); - } - // Reset the clip bounds for the new edges - clipSpan = - clipRect.x_range().clip(x_range(l0, l1).merge(x_range(r0, r1))); - // Reset check condition for next time around. - checkY = min(ceil(min(l1.y, r1.y) - aaRound), clipRect.y1); - } - - // Calculate a potentially AA'd span and check if it is non-empty. - IntRange span = aa_span(fbuf, left, right, clipSpan); - if (span.len() > 0) { - // If user clip planes are enabled, use them to bound the current span. - if (vertex_shader->use_clip_distance()) { - span = span.intersect(clip_distance_range(left, right)); - if (span.len() <= 0) goto next_span; - } - ctx->shaded_rows++; - ctx->shaded_pixels += span.len(); - // Advance color/depth buffer pointers to the start of the span. - P* buf = fbuf + span.start; - // Check if the we will need to use depth-buffer or discard on this span. - DepthRun* depth = - depthtex.buf != nullptr && depthtex.cleared() ? fdepth : nullptr; - bool use_discard = fragment_shader->use_discard(); - if (depth) { - // Perspective may cause the depth value to vary on a per sample basis. - // Ensure the depth row is flattened to allow testing of individual - // samples - if (!depth->is_flat()) { - flatten_depth_runs(depth, depthtex.width); - } - // Advance to the depth sample at the start of the span. - depth += span.start; - } - if (colortex.delay_clear) { - // Delayed clear is enabled for the color buffer. Check if needs clear. - prepare_row<P>(colortex, int(y), span.start, span.end, use_discard, - depth); - } - // Initialize fragment shader interpolants to current span position. - fragment_shader->gl_FragCoord.x = init_interp(span.start + 0.5f, 1); - fragment_shader->gl_FragCoord.y = y; - { - // Calculate the fragment Z and W change per change in fragment X step. - vec2_scalar stepZW = - (right.zw() - left.zw()) * (1.0f / (right.x() - left.x())); - // Calculate initial Z and W values for span start. - vec2_scalar zw = left.zw() + stepZW * (span.start + 0.5f - left.x()); - // Set fragment shader's Z and W values so that it can use them to - // cancel out the 1/w baked into the interpolants. - fragment_shader->gl_FragCoord.z = init_interp(zw.x, stepZW.x); - fragment_shader->gl_FragCoord.w = init_interp(zw.y, stepZW.y); - fragment_shader->swgl_StepZW = stepZW; - // Change in interpolants is difference between current right and left - // edges per the change in right and left X. The left and right - // interpolant values were previously multipled by 1/w, so the step and - // initial span values take this into account. - Interpolants step = - (right.interp - left.interp) * (1.0f / (right.x() - left.x())); - // Advance current interpolants to X at start of span. - Interpolants o = left.interp + step * (span.start + 0.5f - left.x()); - fragment_shader->init_span<true>(&o, &step); - } - clipRect.set_clip_mask(span.start, y, buf); - if (!use_discard) { - // No discard is used. Common case. - draw_span<false, true>(buf, depth, span.len(), packDepth); - } else { - // Discard is used. Rare. - draw_span<true, true>(buf, depth, span.len(), packDepth); - } - } - next_span: - // Advance Y and edge interpolants to next row. - y++; - left.nextRow(); - right.nextRow(); - // Advance buffers to next row. - fbuf += colortex.stride() / sizeof(P); - fdepth += depthtex.stride() / sizeof(DepthRun); - } -} - -// Clip a primitive against both sides of a view-frustum axis, producing -// intermediate vertexes with interpolated attributes that will no longer -// intersect the selected axis planes. This assumes the primitive is convex -// and should produce at most N+2 vertexes for each invocation (only in the -// worst case where one point falls outside on each of the opposite sides -// with the rest of the points inside). The supplied AA edge mask will be -// modified such that it corresponds to the clipped polygon edges. -template <XYZW AXIS> -static int clip_side(int nump, Point3D* p, Interpolants* interp, Point3D* outP, - Interpolants* outInterp, int& outEdgeMask) { - // Potential mask bits of which side of a plane a coordinate falls on. - enum SIDE { POSITIVE = 1, NEGATIVE = 2 }; - int numClip = 0; - int edgeMask = outEdgeMask; - Point3D prev = p[nump - 1]; - Interpolants prevInterp = interp[nump - 1]; - float prevCoord = prev.select(AXIS); - // Coordinate must satisfy -W <= C <= W. Determine if it is outside, and - // if so, remember which side it is outside of. In the special case that W is - // negative and |C| < |W|, both -W <= C and C <= W will be false, such that - // we must consider the coordinate as falling outside of both plane sides - // simultaneously. We test each condition separately and combine them to form - // a mask of which plane sides we exceeded. If we neglect to consider both - // sides simultaneously, points can erroneously oscillate from one plane side - // to the other and exceed the supported maximum number of clip outputs. - int prevMask = (prevCoord < -prev.w ? NEGATIVE : 0) | - (prevCoord > prev.w ? POSITIVE : 0); - // Loop through points, finding edges that cross the planes by evaluating - // the side at each point. - outEdgeMask = 0; - for (int i = 0; i < nump; i++, edgeMask >>= 1) { - Point3D cur = p[i]; - Interpolants curInterp = interp[i]; - float curCoord = cur.select(AXIS); - int curMask = - (curCoord < -cur.w ? NEGATIVE : 0) | (curCoord > cur.w ? POSITIVE : 0); - // Check if the previous and current end points are on different sides. If - // the masks of sides intersect, then we consider them to be on the same - // side. So in the case the masks do not intersect, we then consider them - // to fall on different sides. - if (!(curMask & prevMask)) { - // One of the edge's end points is outside the plane with the other - // inside the plane. Find the offset where it crosses the plane and - // adjust the point and interpolants to there. - if (prevMask) { - // Edge that was previously outside crosses inside. - // Evaluate plane equation for previous and current end-point - // based on previous side and calculate relative offset. - if (numClip >= nump + 2) { - // If for some reason we produced more vertexes than we support, just - // bail out. - assert(false); - return 0; - } - // The positive plane is assigned the sign 1, and the negative plane is - // assigned -1. If the point falls outside both planes, that means W is - // negative. To compensate for this, we must interpolate the coordinate - // till W=0, at which point we can choose a single plane side for the - // coordinate to fall on since W will no longer be negative. To compute - // the coordinate where W=0, we compute K = prev.w / (prev.w-cur.w) and - // interpolate C = prev.C + K*(cur.C - prev.C). The sign of C will be - // the side of the plane we need to consider. Substituting K into the - // comparison C < 0, we can then avoid the division in K with a - // cross-multiplication. - float prevSide = - (prevMask & NEGATIVE) && (!(prevMask & POSITIVE) || - prevCoord * (cur.w - prev.w) < - prev.w * (curCoord - prevCoord)) - ? -1 - : 1; - float prevDist = prevCoord - prevSide * prev.w; - float curDist = curCoord - prevSide * cur.w; - // It may happen that after we interpolate by the weight k that due to - // floating point rounding we've underestimated the value necessary to - // push it over the clipping boundary. Just in case, nudge the mantissa - // by a single increment so that we essentially round it up and move it - // further inside the clipping boundary. We use nextafter to do this in - // a portable fashion. - float k = prevDist / (prevDist - curDist); - Point3D clipped = prev + (cur - prev) * k; - if (prevSide * clipped.select(AXIS) > clipped.w) { - k = nextafterf(k, 1.0f); - clipped = prev + (cur - prev) * k; - } - outP[numClip] = clipped; - outInterp[numClip] = prevInterp + (curInterp - prevInterp) * k; - // Don't output the current edge mask since start point was outside. - numClip++; - } - if (curMask) { - // Edge that was previously inside crosses outside. - // Evaluate plane equation for previous and current end-point - // based on current side and calculate relative offset. - if (numClip >= nump + 2) { - assert(false); - return 0; - } - // In the case the coordinate falls on both plane sides, the computation - // here is much the same as for prevSide, but since we are going from a - // previous W that is positive to current W that is negative, then the - // sign of cur.w - prev.w will flip in the equation. The resulting sign - // is negated to compensate for this. - float curSide = - (curMask & POSITIVE) && (!(curMask & NEGATIVE) || - prevCoord * (cur.w - prev.w) < - prev.w * (curCoord - prevCoord)) - ? 1 - : -1; - float prevDist = prevCoord - curSide * prev.w; - float curDist = curCoord - curSide * cur.w; - // Calculate interpolation weight k and the nudge it inside clipping - // boundary with nextafter. Note that since we were previously inside - // and now crossing outside, we have to flip the nudge direction for - // the weight towards 0 instead of 1. - float k = prevDist / (prevDist - curDist); - Point3D clipped = prev + (cur - prev) * k; - if (curSide * clipped.select(AXIS) > clipped.w) { - k = nextafterf(k, 0.0f); - clipped = prev + (cur - prev) * k; - } - outP[numClip] = clipped; - outInterp[numClip] = prevInterp + (curInterp - prevInterp) * k; - // Output the current edge mask since the end point is inside. - outEdgeMask |= (edgeMask & 1) << numClip; - numClip++; - } - } - if (!curMask) { - // The current end point is inside the plane, so output point unmodified. - if (numClip >= nump + 2) { - assert(false); - return 0; - } - outP[numClip] = cur; - outInterp[numClip] = curInterp; - // Output the current edge mask since the end point is inside. - outEdgeMask |= (edgeMask & 1) << numClip; - numClip++; - } - prev = cur; - prevInterp = curInterp; - prevCoord = curCoord; - prevMask = curMask; - } - return numClip; -} - -// Helper function to dispatch to perspective span drawing with points that -// have already been transformed and clipped. -static inline void draw_perspective_clipped(int nump, Point3D* p_clip, - Interpolants* interp_clip, - Texture& colortex, - Texture& depthtex) { - // If polygon is ouside clip rect, nothing to draw. - ClipRect clipRect(colortex); - if (!clipRect.overlaps(nump, p_clip)) { - return; - } - - // Finally draw perspective-correct spans for the polygon. - if (colortex.internal_format == GL_RGBA8) { - draw_perspective_spans<uint32_t>(nump, p_clip, interp_clip, colortex, - depthtex, clipRect); - } else if (colortex.internal_format == GL_R8) { - draw_perspective_spans<uint8_t>(nump, p_clip, interp_clip, colortex, - depthtex, clipRect); - } else { - assert(false); - } -} - -// Draws a perspective-correct 3D primitive with varying Z value, as opposed -// to a simple 2D planar primitive with a constant Z value that could be -// trivially Z rejected. This requires clipping the primitive against the near -// and far planes to ensure it stays within the valid Z-buffer range. The Z -// and W of each fragment of the primitives are interpolated across the -// generated spans and then depth-tested as appropriate. -// Additionally, vertex attributes must be interpolated with perspective- -// correction by dividing by W before interpolation, and then later multiplied -// by W again to produce the final correct attribute value for each fragment. -// This process is expensive and should be avoided if possible for primitive -// batches that are known ahead of time to not need perspective-correction. -static void draw_perspective(int nump, Interpolants interp_outs[4], - Texture& colortex, Texture& depthtex) { - // Lines are not supported with perspective. - assert(nump >= 3); - // Convert output of vertex shader to screen space. - vec4 pos = vertex_shader->gl_Position; - vec3_scalar scale = - vec3_scalar(ctx->viewport.width(), ctx->viewport.height(), 1) * 0.5f; - vec3_scalar offset = - make_vec3(make_vec2(ctx->viewport.origin() - colortex.offset), 0.0f) + - scale; - // Verify if point is between near and far planes, rejecting NaN. - if (test_all(pos.z > -pos.w && pos.z < pos.w)) { - // No points cross the near or far planes, so no clipping required. - // Just divide coords by W and convert to viewport. We assume the W - // coordinate is non-zero and the reciprocal is finite since it would - // otherwise fail the test_none condition. - Float w = 1.0f / pos.w; - vec3 screen = pos.sel(X, Y, Z) * w * scale + offset; - Point3D p[4] = {{screen.x.x, screen.y.x, screen.z.x, w.x}, - {screen.x.y, screen.y.y, screen.z.y, w.y}, - {screen.x.z, screen.y.z, screen.z.z, w.z}, - {screen.x.w, screen.y.w, screen.z.w, w.w}}; - draw_perspective_clipped(nump, p, interp_outs, colortex, depthtex); - } else { - // Points cross the near or far planes, so we need to clip. - // Start with the original 3 or 4 points... - Point3D p[4] = {{pos.x.x, pos.y.x, pos.z.x, pos.w.x}, - {pos.x.y, pos.y.y, pos.z.y, pos.w.y}, - {pos.x.z, pos.y.z, pos.z.z, pos.w.z}, - {pos.x.w, pos.y.w, pos.z.w, pos.w.w}}; - // Clipping can expand the points by 1 for each of 6 view frustum planes. - Point3D p_clip[4 + 6]; - Interpolants interp_clip[4 + 6]; - // Clip against near and far Z planes. - nump = clip_side<Z>(nump, p, interp_outs, p_clip, interp_clip, - swgl_AAEdgeMask); - // If no points are left inside the view frustum, there's nothing to draw. - if (nump < 3) { - return; - } - // After clipping against only the near and far planes, we might still - // produce points where W = 0, exactly at the camera plane. OpenGL specifies - // that for clip coordinates, points must satisfy: - // -W <= X <= W - // -W <= Y <= W - // -W <= Z <= W - // When Z = W = 0, this is trivially satisfied, but when we transform and - // divide by W below it will produce a divide by 0. Usually we want to only - // clip Z to avoid the extra work of clipping X and Y. We can still project - // points that fall outside the view frustum X and Y so long as Z is valid. - // The span drawing code will then ensure X and Y are clamped to viewport - // boundaries. However, in the Z = W = 0 case, sometimes clipping X and Y, - // will push W further inside the view frustum so that it is no longer 0, - // allowing us to finally proceed to projecting the points to the screen. - for (int i = 0; i < nump; i++) { - // Found an invalid W, so need to clip against X and Y... - if (p_clip[i].w <= 0.0f) { - // Ping-pong p_clip -> p_tmp -> p_clip. - Point3D p_tmp[4 + 6]; - Interpolants interp_tmp[4 + 6]; - nump = clip_side<X>(nump, p_clip, interp_clip, p_tmp, interp_tmp, - swgl_AAEdgeMask); - if (nump < 3) return; - nump = clip_side<Y>(nump, p_tmp, interp_tmp, p_clip, interp_clip, - swgl_AAEdgeMask); - if (nump < 3) return; - // After clipping against X and Y planes, there's still points left - // to draw, so proceed to trying projection now... - break; - } - } - // Divide coords by W and convert to viewport. - for (int i = 0; i < nump; i++) { - float w = 1.0f / p_clip[i].w; - // If the W coord is essentially zero, small enough that division would - // result in Inf/NaN, then just set the reciprocal itself to zero so that - // the coordinates becomes zeroed out, as the only valid point that - // satisfies -W <= X/Y/Z <= W is all zeroes. - if (!isfinite(w)) w = 0.0f; - p_clip[i] = Point3D(p_clip[i].sel(X, Y, Z) * w * scale + offset, w); - } - draw_perspective_clipped(nump, p_clip, interp_clip, colortex, depthtex); - } -} - -static void draw_quad(int nump, Texture& colortex, Texture& depthtex) { - // Run vertex shader once for the primitive's vertices. - // Reserve space for 6 sets of interpolants, in case we need to clip against - // near and far planes in the perspective case. - Interpolants interp_outs[4]; - swgl_ClipFlags = 0; - vertex_shader->run_primitive((char*)interp_outs, sizeof(Interpolants)); - vec4 pos = vertex_shader->gl_Position; - // Check if any vertex W is different from another. If so, use perspective. - if (test_any(pos.w != pos.w.x)) { - draw_perspective(nump, interp_outs, colortex, depthtex); - return; - } - - // Convert output of vertex shader to screen space. - // Divide coords by W and convert to viewport. - float w = 1.0f / pos.w.x; - // If the W coord is essentially zero, small enough that division would - // result in Inf/NaN, then just set the reciprocal itself to zero so that - // the coordinates becomes zeroed out, as the only valid point that - // satisfies -W <= X/Y/Z <= W is all zeroes. - if (!isfinite(w)) w = 0.0f; - vec2 screen = (pos.sel(X, Y) * w + 1) * 0.5f * - vec2_scalar(ctx->viewport.width(), ctx->viewport.height()) + - make_vec2(ctx->viewport.origin() - colortex.offset); - Point2D p[4] = {{screen.x.x, screen.y.x}, - {screen.x.y, screen.y.y}, - {screen.x.z, screen.y.z}, - {screen.x.w, screen.y.w}}; - - // If quad is ouside clip rect, nothing to draw. - ClipRect clipRect(colortex); - if (!clipRect.overlaps(nump, p)) { - return; - } - - // Since the quad is assumed 2D, Z is constant across the quad. - float screenZ = (pos.z.x * w + 1) * 0.5f; - if (screenZ < 0 || screenZ > 1) { - // Z values would cross the near or far plane, so just bail. - return; - } - // Since Z doesn't need to be interpolated, just set the fragment shader's - // Z and W values here, once and for all fragment shader invocations. - uint32_t z = uint32_t(MAX_DEPTH_VALUE * screenZ); - fragment_shader->gl_FragCoord.z = screenZ; - fragment_shader->gl_FragCoord.w = w; - - // If supplied a line, adjust it so that it is a quad at least 1 pixel thick. - // Assume that for a line that all 4 SIMD lanes were actually filled with - // vertexes 0, 1, 1, 0. - if (nump == 2) { - // Nudge Y height to span at least 1 pixel by advancing to next pixel - // boundary so that we step at least 1 row when drawing spans. - if (int(p[0].y + 0.5f) == int(p[1].y + 0.5f)) { - p[2].y = 1 + int(p[1].y + 0.5f); - p[3].y = p[2].y; - // Nudge X width to span at least 1 pixel so that rounded coords fall on - // separate pixels. - if (int(p[0].x + 0.5f) == int(p[1].x + 0.5f)) { - p[1].x += 1.0f; - p[2].x += 1.0f; - } - } else { - // If the line already spans at least 1 row, then assume line is vertical - // or diagonal and just needs to be dilated horizontally. - p[2].x += 1.0f; - p[3].x += 1.0f; - } - // Pretend that it's a quad now... - nump = 4; - } - - // Finally draw 2D spans for the quad. Currently only supports drawing to - // RGBA8 and R8 color buffers. - if (colortex.internal_format == GL_RGBA8) { - draw_quad_spans<uint32_t>(nump, p, z, interp_outs, colortex, depthtex, - clipRect); - } else if (colortex.internal_format == GL_R8) { - draw_quad_spans<uint8_t>(nump, p, z, interp_outs, colortex, depthtex, - clipRect); - } else { - assert(false); - } -} - -template <typename INDEX> -static inline void draw_elements(GLsizei count, GLsizei instancecount, - size_t offset, VertexArray& v, - Texture& colortex, Texture& depthtex) { - Buffer& indices_buf = ctx->buffers[v.element_array_buffer_binding]; - if (!indices_buf.buf || offset >= indices_buf.size) { - return; - } - assert((offset & (sizeof(INDEX) - 1)) == 0); - INDEX* indices = (INDEX*)(indices_buf.buf + offset); - count = min(count, (GLsizei)((indices_buf.size - offset) / sizeof(INDEX))); - // Triangles must be indexed at offsets 0, 1, 2. - // Quads must be successive triangles indexed at offsets 0, 1, 2, 2, 1, 3. - if (count == 6 && indices[1] == indices[0] + 1 && - indices[2] == indices[0] + 2 && indices[5] == indices[0] + 3) { - assert(indices[3] == indices[0] + 2 && indices[4] == indices[0] + 1); - // Fast path - since there is only a single quad, we only load per-vertex - // attribs once for all instances, as they won't change across instances - // or within an instance. - vertex_shader->load_attribs(v.attribs, indices[0], 0, 4); - draw_quad(4, colortex, depthtex); - for (GLsizei instance = 1; instance < instancecount; instance++) { - vertex_shader->load_attribs(v.attribs, indices[0], instance, 0); - draw_quad(4, colortex, depthtex); - } - } else { - for (GLsizei instance = 0; instance < instancecount; instance++) { - for (GLsizei i = 0; i + 3 <= count; i += 3) { - if (indices[i + 1] != indices[i] + 1 || - indices[i + 2] != indices[i] + 2) { - continue; - } - if (i + 6 <= count && indices[i + 5] == indices[i] + 3) { - assert(indices[i + 3] == indices[i] + 2 && - indices[i + 4] == indices[i] + 1); - vertex_shader->load_attribs(v.attribs, indices[i], instance, 4); - draw_quad(4, colortex, depthtex); - i += 3; - } else { - vertex_shader->load_attribs(v.attribs, indices[i], instance, 3); - draw_quad(3, colortex, depthtex); - } - } - } - } -} |