| /* |
| * Copyright 2017 Google Inc. |
| * |
| * Use of this source code is governed by a BSD-style license that can be |
| * found in the LICENSE file. |
| */ |
| |
| #include "GrCCPRTriangleShader.h" |
| |
| #include "glsl/GrGLSLFragmentShaderBuilder.h" |
| #include "glsl/GrGLSLVertexGeoBuilder.h" |
| |
| void GrCCPRTriangleShader::appendInputPointFetch(const GrCCPRCoverageProcessor& proc, |
| GrGLSLShaderBuilder* s, |
| const TexelBufferHandle& pointsBuffer, |
| const char* pointId) const { |
| s->appendTexelFetch(pointsBuffer, |
| SkStringPrintf("%s[%s]", proc.instanceAttrib(), pointId).c_str()); |
| } |
| |
| void GrCCPRTriangleShader::emitWind(GrGLSLShaderBuilder* s, const char* pts, |
| const char* outputWind) const { |
| s->codeAppendf("%s = sign(determinant(float2x2(%s[1] - %s[0], %s[2] - %s[0])));", |
| outputWind, pts, pts, pts, pts); |
| } |
| |
| GrCCPRTriangleHullShader::WindHandling |
| GrCCPRTriangleHullShader::onEmitVaryings(GrGLSLVaryingHandler*, SkString* code, |
| const char* /*position*/, const char* /*coverage*/, |
| const char* /*wind*/) { |
| return WindHandling::kNotHandled; // No varyings.Let the base class handle wind. |
| } |
| |
| void GrCCPRTriangleHullShader::onEmitFragmentCode(GrGLSLPPFragmentBuilder* f, |
| const char* outputCoverage) const { |
| f->codeAppendf("%s = 1;", outputCoverage); |
| } |
| |
| GrCCPRTriangleEdgeShader::WindHandling |
| GrCCPRTriangleEdgeShader::onEmitVaryings(GrGLSLVaryingHandler* varyingHandler, SkString* code, |
| const char* position, const char* coverage, |
| const char* wind) { |
| varyingHandler->addVarying("coverage_times_wind", &fCoverageTimesWind); |
| code->appendf("%s = %s * %s;", fCoverageTimesWind.gsOut(), coverage, wind); |
| return WindHandling::kHandled; |
| } |
| |
| void GrCCPRTriangleEdgeShader::onEmitFragmentCode(GrGLSLPPFragmentBuilder* f, |
| const char* outputCoverage) const { |
| f->codeAppendf("%s = %s;", outputCoverage, fCoverageTimesWind.fsIn()); |
| } |
| |
| void GrCCPRTriangleCornerShader::emitSetupCode(GrGLSLShaderBuilder* s, const char* pts, |
| const char* cornerId, const char* wind, |
| GeometryVars* vars) const { |
| s->codeAppendf("float2 corner = %s[sk_InvocationID];", pts); |
| vars->fCornerVars.fPoint = "corner"; |
| |
| s->codeAppendf("float2x2 vectors = float2x2(corner - %s[(sk_InvocationID + 2) %% 3], " |
| "corner - %s[(sk_InvocationID + 1) %% 3]);", |
| pts, pts); |
| |
| // Make sure neither vector is 0 to avoid a divide-by-zero. Wind will be zero anyway if this |
| // is the case, so whatever we output won't have any effect as long it isn't NaN or Inf. |
| s->codeAppend ("for (int i = 0; i < 2; ++i) {"); |
| s->codeAppend ( "vectors[i] = (vectors[i] != float2(0)) ? vectors[i] : float2(1);"); |
| s->codeAppend ("}"); |
| |
| // Find the vector that bisects the region outside the incoming edges. Each edge is |
| // responsible to subtract the outside region on its own the side of the bisector. |
| s->codeAppendf("float2 leftdir = normalize(vectors[%s > 0 ? 0 : 1]);", wind); |
| s->codeAppendf("float2 rightdir = normalize(vectors[%s > 0 ? 1 : 0]);", wind); |
| s->codeAppend ("float2 bisect = dot(leftdir, rightdir) >= 0 ? " |
| "leftdir + rightdir : " |
| "float2(leftdir.y - rightdir.y, rightdir.x - leftdir.x);"); |
| |
| // In ccpr we don't calculate exact geometric pixel coverage. What the distance-to-edge |
| // method actually finds is coverage inside a logical "AA box", one that is rotated inline |
| // with the edge, and in our case, up-scaled to circumscribe the actual pixel. Below we set |
| // up transformations into normalized logical AA box space for both incoming edges. These |
| // will tell the fragment shader where the corner is located within each edge's AA box. |
| s->declareGlobal(fAABoxMatrices); |
| s->declareGlobal(fAABoxTranslates); |
| s->declareGlobal(fGeoShaderBisects); |
| s->codeAppendf("for (int i = 0; i < 2; ++i) {"); |
| // The X component runs parallel to the edge (i.e. distance to the corner). |
| s->codeAppendf( "float2 n = -vectors[%s > 0 ? i : 1 - i];", wind); |
| s->codeAppend ( "float nwidth = (abs(n.x) + abs(n.y)) * (bloat * 2);"); |
| s->codeAppend ( "n /= nwidth;"); // nwidth != 0 because both vectors != 0. |
| s->codeAppendf( "%s[i][0] = n;", fAABoxMatrices.c_str()); |
| s->codeAppendf( "%s[i][0] = -dot(n, corner) + .5;", fAABoxTranslates.c_str()); |
| |
| // The Y component runs perpendicular to the edge (i.e. distance-to-edge). |
| s->codeAppend ( "n = (i == 0) ? float2(-n.y, n.x) : float2(n.y, -n.x);"); |
| s->codeAppendf( "%s[i][1] = n;", fAABoxMatrices.c_str()); |
| s->codeAppendf( "%s[i][1] = -dot(n, corner) + .5;", fAABoxTranslates.c_str()); |
| |
| // Translate the bisector into logical AA box space. |
| // NOTE: Since the region outside two edges of a convex shape is in [180 deg, 360 deg], the |
| // bisector will therefore be in [90 deg, 180 deg]. Or, x >= 0 and y <= 0 in AA box space. |
| s->codeAppendf( "%s[i] = -bisect * %s[i];", |
| fGeoShaderBisects.c_str(), fAABoxMatrices.c_str()); |
| s->codeAppend ("}"); |
| } |
| |
| GrCCPRTriangleCornerShader::WindHandling |
| GrCCPRTriangleCornerShader::onEmitVaryings(GrGLSLVaryingHandler* varyingHandler, SkString* code, |
| const char* position, const char* /*coverage*/, |
| const char* /*wind*/) { |
| varyingHandler->addVarying("corner_location_in_aa_boxes", &fCornerLocationInAABoxes); |
| varyingHandler->addFlatVarying("bisect_in_aa_boxes", &fBisectInAABoxes); |
| code->appendf("for (int i = 0; i < 2; ++i) {"); |
| code->appendf( "%s[i] = %s * %s[i] + %s[i];", |
| fCornerLocationInAABoxes.gsOut(), position, fAABoxMatrices.c_str(), |
| fAABoxTranslates.c_str()); |
| code->appendf( "%s[i] = %s[i];", fBisectInAABoxes.gsOut(), fGeoShaderBisects.c_str()); |
| code->appendf("}"); |
| |
| return WindHandling::kNotHandled; |
| } |
| |
| void GrCCPRTriangleCornerShader::onEmitFragmentCode(GrGLSLPPFragmentBuilder* f, |
| const char* outputCoverage) const { |
| // By the time we reach this shader, the pixel is in the following state: |
| // |
| // 1. The hull shader has emitted a coverage of 1. |
| // 2. Both edges have subtracted the area on their outside. |
| // |
| // This generally works, but it is a problem for corner pixels. There is a region within |
| // corner pixels that is outside both edges at the same time. This means the region has been |
| // double subtracted (once by each edge). The purpose of this shader is to fix these corner |
| // pixels. |
| // |
| // More specifically, each edge redoes its coverage analysis so that it only subtracts the |
| // outside area that falls on its own side of the bisector line. |
| // |
| // NOTE: unless the edges fall on multiples of 90 deg from one another, they will have |
| // different AA boxes. (For an explanation of AA boxes, see comments in |
| // onEmitGeometryShader.) This means the coverage analysis will only be approximate. It |
| // seems acceptable, but if we want exact coverage we will need to switch to a more |
| // expensive model. |
| f->codeAppendf("for (int i = 0; i < 2; ++i) {"); // Loop through both edges. |
| f->codeAppendf( "half2 corner = %s[i];", fCornerLocationInAABoxes.fsIn()); |
| f->codeAppendf( "half2 bisect = %s[i];", fBisectInAABoxes.fsIn()); |
| |
| // Find the point at which the bisector exits the logical AA box. |
| // (The inequality works because bisect.x is known >= 0 and bisect.y is known <= 0.) |
| f->codeAppendf( "half2 d = half2(1 - corner.x, -corner.y);"); |
| f->codeAppendf( "half T = d.y * bisect.x >= d.x * bisect.y ? d.y / bisect.y " |
| ": d.x / bisect.x;"); |
| f->codeAppendf( "half2 exit = corner + bisect * T;"); |
| |
| // These lines combined (and the final multiply by .5) accomplish the following: |
| // 1. Add back the area beyond the corner that was subtracted out previously. |
| // 2. Subtract out the area beyond the corner, but under the bisector. |
| // The other edge will take care of the area on its own side of the bisector. |
| f->codeAppendf( "%s += (2 - corner.x - exit.x) * corner.y;", outputCoverage); |
| f->codeAppendf( "%s += (corner.x - 1) * exit.y;", outputCoverage); |
| f->codeAppendf("}"); |
| |
| f->codeAppendf("%s *= .5;", outputCoverage); |
| } |