/*
* 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 "GrCCCoverageProcessor.h"
#include "GrGpuCommandBuffer.h"
#include "GrOpFlushState.h"
#include "SkMakeUnique.h"
#include "ccpr/GrCCConicShader.h"
#include "ccpr/GrCCCubicShader.h"
#include "ccpr/GrCCQuadraticShader.h"
#include "glsl/GrGLSLVertexGeoBuilder.h"
#include "glsl/GrGLSLFragmentShaderBuilder.h"
#include "glsl/GrGLSLVertexGeoBuilder.h"
class GrCCCoverageProcessor::TriangleShader : public GrCCCoverageProcessor::Shader {
void onEmitVaryings(GrGLSLVaryingHandler* varyingHandler, GrGLSLVarying::Scope scope,
SkString* code, const char* position, const char* coverage,
const char* cornerCoverage) override {
if (!cornerCoverage) {
fCoverages.reset(kHalf_GrSLType, scope);
varyingHandler->addVarying("coverage", &fCoverages);
code->appendf("%s = %s;", OutName(fCoverages), coverage);
} else {
fCoverages.reset(kHalf3_GrSLType, scope);
varyingHandler->addVarying("coverages", &fCoverages);
code->appendf("%s = half3(%s, %s);", OutName(fCoverages), coverage, cornerCoverage);
}
}
void onEmitFragmentCode(GrGLSLFPFragmentBuilder* f, const char* outputCoverage) const override {
if (kHalf_GrSLType == fCoverages.type()) {
f->codeAppendf("%s = %s;", outputCoverage, fCoverages.fsIn());
} else {
f->codeAppendf("%s = %s.z * %s.y + %s.x;",
outputCoverage, fCoverages.fsIn(), fCoverages.fsIn(), fCoverages.fsIn());
}
}
GrGLSLVarying fCoverages;
};
void GrCCCoverageProcessor::Shader::CalcWind(const GrCCCoverageProcessor& proc,
GrGLSLVertexGeoBuilder* s, const char* pts,
const char* outputWind) {
if (3 == proc.numInputPoints()) {
s->codeAppendf("float2 a = %s[0] - %s[1], "
"b = %s[0] - %s[2];", pts, pts, pts, pts);
} else {
// All inputs are convex, so it's sufficient to just average the middle two input points.
SkASSERT(4 == proc.numInputPoints());
s->codeAppendf("float2 p12 = (%s[1] + %s[2]) * .5;", pts, pts);
s->codeAppendf("float2 a = %s[0] - p12, "
"b = %s[0] - %s[3];", pts, pts, pts);
}
s->codeAppend ("float area_x2 = determinant(float2x2(a, b));");
if (proc.isTriangles()) {
// We cull extremely thin triangles by zeroing wind. When a triangle gets too thin it's
// possible for FP round-off error to actually give us the wrong winding direction, causing
// rendering artifacts. The criteria we choose is "height <~ 1/1024". So we drop a triangle
// if the max effect it can have on any single pixel is <~ 1/1024, or 1/4 of a bit in 8888.
s->codeAppend ("float2 bbox_size = max(abs(a), abs(b));");
s->codeAppend ("float basewidth = max(bbox_size.x + bbox_size.y, 1);");
s->codeAppendf("%s = (abs(area_x2 * 1024) > basewidth) ? sign(half(area_x2)) : 0;",
outputWind);
} else {
// We already converted nearly-flat curves to lines on the CPU, so no need to worry about
// thin curve hulls at this point.
s->codeAppendf("%s = sign(half(area_x2));", outputWind);
}
}
void GrCCCoverageProcessor::Shader::EmitEdgeDistanceEquation(GrGLSLVertexGeoBuilder* s,
const char* leftPt,
const char* rightPt,
const char* outputDistanceEquation) {
s->codeAppendf("float2 n = float2(%s.y - %s.y, %s.x - %s.x);",
rightPt, leftPt, leftPt, rightPt);
s->codeAppend ("float nwidth = (abs(n.x) + abs(n.y)) * (bloat * 2);");
// When nwidth=0, wind must also be 0 (and coverage * wind = 0). So it doesn't matter what we
// come up with here as long as it isn't NaN or Inf.
s->codeAppend ("n /= (0 != nwidth) ? nwidth : 1;");
s->codeAppendf("%s = float3(-n, dot(n, %s) - .5);", outputDistanceEquation, leftPt);
}
void GrCCCoverageProcessor::Shader::CalcEdgeCoverageAtBloatVertex(GrGLSLVertexGeoBuilder* s,
const char* leftPt,
const char* rightPt,
const char* rasterVertexDir,
const char* outputCoverage) {
// Here we find an edge's coverage at one corner of a conservative raster bloat box whose center
// falls on the edge in question. (A bloat box is axis-aligned and the size of one pixel.) We
// always set up coverage so it is -1 at the outermost corner, 0 at the innermost, and -.5 at
// the center. Interpolated, these coverage values convert jagged conservative raster edges into
// smooth antialiased edges.
//
// d1 == (P + sign(n) * bloat) dot n (Distance at the bloat box vertex whose
// == P dot n + (abs(n.x) + abs(n.y)) * bloatSize coverage=-1, where the bloat box is
// centered on P.)
//
// d0 == (P - sign(n) * bloat) dot n (Distance at the bloat box vertex whose
// == P dot n - (abs(n.x) + abs(n.y)) * bloatSize coverage=0, where the bloat box is
// centered on P.)
//
// d == (P + rasterVertexDir * bloatSize) dot n (Distance at the bloat box vertex whose
// == P dot n + (rasterVertexDir dot n) * bloatSize coverage we wish to calculate.)
//
// coverage == -(d - d0) / (d1 - d0) (coverage=-1 at d=d1; coverage=0 at d=d0)
//
// == (rasterVertexDir dot n) / (abs(n.x) + abs(n.y)) * -.5 - .5
//
s->codeAppendf("float2 n = float2(%s.y - %s.y, %s.x - %s.x);",
rightPt, leftPt, leftPt, rightPt);
s->codeAppend ("float nwidth = abs(n.x) + abs(n.y);");
s->codeAppendf("float t = dot(%s, n);", rasterVertexDir);
// The below conditional guarantees we get exactly 1 on the divide when nwidth=t (in case the
// GPU divides by multiplying by the reciprocal?) It also guards against NaN when nwidth=0.
s->codeAppendf("%s = half(abs(t) != nwidth ? t / nwidth : sign(t)) * -.5 - .5;",
outputCoverage);
}
void GrCCCoverageProcessor::Shader::CalcEdgeCoveragesAtBloatVertices(GrGLSLVertexGeoBuilder* s,
const char* leftPt,
const char* rightPt,
const char* bloatDir1,
const char* bloatDir2,
const char* outputCoverages) {
// See comments in CalcEdgeCoverageAtBloatVertex.
s->codeAppendf("float2 n = float2(%s.y - %s.y, %s.x - %s.x);",
rightPt, leftPt, leftPt, rightPt);
s->codeAppend ("float nwidth = abs(n.x) + abs(n.y);");
s->codeAppendf("float2 t = n * float2x2(%s, %s);", bloatDir1, bloatDir2);
s->codeAppendf("for (int i = 0; i < 2; ++i) {");
s->codeAppendf( "%s[i] = half(abs(t[i]) != nwidth ? t[i] / nwidth : sign(t[i])) * -.5 - .5;",
outputCoverages);
s->codeAppendf("}");
}
void GrCCCoverageProcessor::Shader::CalcCornerAttenuation(GrGLSLVertexGeoBuilder* s,
const char* leftDir, const char* rightDir,
const char* outputAttenuation) {
// obtuseness = cos(corner_angle) if corner_angle > 90 degrees
// 0 if corner_angle <= 90 degrees
//
// NOTE: leftDir and rightDir are normalized and point in the same direction the path was
// defined with, i.e., leftDir points into the corner and rightDir points away from the corner.
s->codeAppendf("half obtuseness = max(half(dot(%s, %s)), 0);", leftDir, rightDir);
// axis_alignedness = 1 - tan(angle_to_nearest_axis_from_corner_bisector)
// (i.e., 1 when the corner bisector is aligned with the x- or y-axis
// 0 when the corner bisector falls on a 45 degree angle
// 0..1 when the corner bisector falls somewhere in between
s->codeAppendf("half2 abs_bisect_maybe_transpose = abs((0 == obtuseness) ? half2(%s - %s) : "
"half2(%s + %s));",
leftDir, rightDir, leftDir, rightDir);
s->codeAppend ("half axis_alignedness = "
"1 - min(abs_bisect_maybe_transpose.y, abs_bisect_maybe_transpose.x) / "
"max(abs_bisect_maybe_transpose.x, abs_bisect_maybe_transpose.y);");
// ninety_degreesness = sin^2(corner_angle)
// sin^2 just because... it's always positive and the results looked better than plain sine... ?
s->codeAppendf("half ninety_degreesness = determinant(half2x2(%s, %s));", leftDir, rightDir);
s->codeAppend ("ninety_degreesness = ninety_degreesness * ninety_degreesness;");
// The below formula is not smart. It was just arrived at by considering the following
// observations:
//
// 1. 90-degree, axis-aligned corners have full attenuation along the bisector.
// (i.e. coverage = 1 - distance_to_corner^2)
// (i.e. outputAttenuation = 0)
//
// 2. 180-degree corners always have zero attenuation.
// (i.e. coverage = 1 - distance_to_corner)
// (i.e. outputAttenuation = 1)
//
// 3. 90-degree corners whose bisector falls on a 45 degree angle also do not attenuate.
// (i.e. outputAttenuation = 1)
s->codeAppendf("%s = max(obtuseness, axis_alignedness * ninety_degreesness);",
outputAttenuation);
}
void GrCCCoverageProcessor::getGLSLProcessorKey(const GrShaderCaps&,
GrProcessorKeyBuilder* b) const {
int key = (int)fPrimitiveType << 2;
if (GSSubpass::kCorners == fGSSubpass) {
key |= 2;
}
if (Impl::kVertexShader == fImpl) {
key |= 1;
}
#ifdef SK_DEBUG
uint32_t bloatBits;
memcpy(&bloatBits, &fDebugBloat, 4);
b->add32(bloatBits);
#endif
b->add32(key);
}
GrGLSLPrimitiveProcessor* GrCCCoverageProcessor::createGLSLInstance(const GrShaderCaps&) const {
std::unique_ptr<Shader> shader;
switch (fPrimitiveType) {
case PrimitiveType::kTriangles:
case PrimitiveType::kWeightedTriangles:
shader = skstd::make_unique<TriangleShader>();
break;
case PrimitiveType::kQuadratics:
shader = skstd::make_unique<GrCCQuadraticShader>();
break;
case PrimitiveType::kCubics:
shader = skstd::make_unique<GrCCCubicShader>();
break;
case PrimitiveType::kConics:
shader = skstd::make_unique<GrCCConicShader>();
break;
}
return Impl::kGeometryShader == fImpl ? this->createGSImpl(std::move(shader))
: this->createVSImpl(std::move(shader));
}
void GrCCCoverageProcessor::Shader::emitFragmentCode(const GrCCCoverageProcessor& proc,
GrGLSLFPFragmentBuilder* f,
const char* skOutputColor,
const char* skOutputCoverage) const {
f->codeAppendf("half coverage = 0;");
this->onEmitFragmentCode(f, "coverage");
f->codeAppendf("%s.a = coverage;", skOutputColor);
f->codeAppendf("%s = half4(1);", skOutputCoverage);
}
void GrCCCoverageProcessor::draw(GrOpFlushState* flushState, const GrPipeline& pipeline,
const SkIRect scissorRects[], const GrMesh meshes[], int meshCount,
const SkRect& drawBounds) const {
GrPipeline::DynamicStateArrays dynamicStateArrays;
dynamicStateArrays.fScissorRects = scissorRects;
GrGpuRTCommandBuffer* cmdBuff = flushState->rtCommandBuffer();
cmdBuff->draw(*this, pipeline, nullptr, &dynamicStateArrays, meshes, meshCount, drawBounds);
// Geometry shader backend draws primitives in two subpasses.
if (Impl::kGeometryShader == fImpl) {
SkASSERT(GSSubpass::kHulls == fGSSubpass);
GrCCCoverageProcessor cornerProc(*this, GSSubpass::kCorners);
cmdBuff->draw(cornerProc, pipeline, nullptr, &dynamicStateArrays, meshes, meshCount,
drawBounds);
}
}