/*
* 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 "GrMesh.h"
#include "glsl/GrGLSLVertexGeoBuilder.h"
using InputType = GrGLSLGeometryBuilder::InputType;
using OutputType = GrGLSLGeometryBuilder::OutputType;
/**
* This class and its subclasses implement the coverage processor with geometry shaders.
*/
class GrCCCoverageProcessor::GSImpl : public GrGLSLGeometryProcessor {
protected:
GSImpl(std::unique_ptr<Shader> shader) : fShader(std::move(shader)) {}
virtual bool hasCoverage() const { return false; }
void setData(const GrGLSLProgramDataManager& pdman, const GrPrimitiveProcessor&,
FPCoordTransformIter&& transformIter) final {
this->setTransformDataHelper(SkMatrix::I(), pdman, &transformIter);
}
void onEmitCode(EmitArgs& args, GrGPArgs* gpArgs) final {
const GrCCCoverageProcessor& proc = args.fGP.cast<GrCCCoverageProcessor>();
// The vertex shader simply forwards transposed x or y values to the geometry shader.
SkASSERT(1 == proc.numVertexAttributes());
gpArgs->fPositionVar = proc.fVertexAttribute.asShaderVar();
// Geometry shader.
GrGLSLVaryingHandler* varyingHandler = args.fVaryingHandler;
this->emitGeometryShader(proc, varyingHandler, args.fGeomBuilder, args.fRTAdjustName);
varyingHandler->emitAttributes(proc);
varyingHandler->setNoPerspective();
SkASSERT(!args.fFPCoordTransformHandler->nextCoordTransform());
// Fragment shader.
fShader->emitFragmentCode(proc, args.fFragBuilder, args.fOutputColor, args.fOutputCoverage);
}
void emitGeometryShader(const GrCCCoverageProcessor& proc,
GrGLSLVaryingHandler* varyingHandler, GrGLSLGeometryBuilder* g,
const char* rtAdjust) const {
int numInputPoints = proc.numInputPoints();
SkASSERT(3 == numInputPoints || 4 == numInputPoints);
int inputWidth = (4 == numInputPoints || proc.hasInputWeight()) ? 4 : 3;
const char* posValues = (4 == inputWidth) ? "sk_Position" : "sk_Position.xyz";
g->codeAppendf("float%ix2 pts = transpose(float2x%i(sk_in[0].%s, sk_in[1].%s));",
inputWidth, inputWidth, posValues, posValues);
GrShaderVar wind("wind", kHalf_GrSLType);
g->declareGlobal(wind);
Shader::CalcWind(proc, g, "pts", wind.c_str());
if (PrimitiveType::kWeightedTriangles == proc.fPrimitiveType) {
SkASSERT(3 == numInputPoints);
SkASSERT(kFloat4_GrVertexAttribType == proc.fVertexAttribute.cpuType());
g->codeAppendf("%s *= half(sk_in[0].sk_Position.w);", wind.c_str());
}
SkString emitVertexFn;
SkSTArray<2, GrShaderVar> emitArgs;
const char* corner = emitArgs.emplace_back("corner", kFloat2_GrSLType).c_str();
const char* bloatdir = emitArgs.emplace_back("bloatdir", kFloat2_GrSLType).c_str();
const char* coverage = nullptr;
if (this->hasCoverage()) {
coverage = emitArgs.emplace_back("coverage", kHalf_GrSLType).c_str();
}
const char* cornerCoverage = nullptr;
if (GSSubpass::kCorners == proc.fGSSubpass) {
cornerCoverage = emitArgs.emplace_back("corner_coverage", kHalf2_GrSLType).c_str();
}
g->emitFunction(kVoid_GrSLType, "emitVertex", emitArgs.count(), emitArgs.begin(), [&]() {
SkString fnBody;
if (coverage) {
fnBody.appendf("%s *= %s;", coverage, wind.c_str());
}
if (cornerCoverage) {
fnBody.appendf("%s.x *= %s;", cornerCoverage, wind.c_str());
}
fnBody.appendf("float2 vertexpos = fma(%s, float2(bloat), %s);", bloatdir, corner);
fShader->emitVaryings(varyingHandler, GrGLSLVarying::Scope::kGeoToFrag, &fnBody,
"vertexpos", coverage ? coverage : wind.c_str(), cornerCoverage);
g->emitVertex(&fnBody, "vertexpos", rtAdjust);
return fnBody;
}().c_str(), &emitVertexFn);
float bloat = kAABloatRadius;
#ifdef SK_DEBUG
if (proc.debugBloatEnabled()) {
bloat *= proc.debugBloat();
}
#endif
g->defineConstant("bloat", bloat);
this->onEmitGeometryShader(proc, g, wind, emitVertexFn.c_str());
}
virtual void onEmitGeometryShader(const GrCCCoverageProcessor&, GrGLSLGeometryBuilder*,
const GrShaderVar& wind, const char* emitVertexFn) const = 0;
virtual ~GSImpl() {}
const std::unique_ptr<Shader> fShader;
typedef GrGLSLGeometryProcessor INHERITED;
};
/**
* Generates conservative rasters around a triangle and its edges, and calculates coverage ramps.
*
* Triangle rough outlines are drawn in two steps: (1) draw a conservative raster of the entire
* triangle, with a coverage of +1, and (2) draw conservative rasters around each edge, with a
* coverage ramp from -1 to 0. These edge coverage values convert jagged conservative raster edges
* into smooth, antialiased ones.
*
* The final corners get touched up in a later step by GSTriangleCornerImpl.
*/
class GrCCCoverageProcessor::GSTriangleHullImpl : public GrCCCoverageProcessor::GSImpl {
public:
GSTriangleHullImpl(std::unique_ptr<Shader> shader) : GSImpl(std::move(shader)) {}
bool hasCoverage() const override { return true; }
void onEmitGeometryShader(const GrCCCoverageProcessor&, GrGLSLGeometryBuilder* g,
const GrShaderVar& wind, const char* emitVertexFn) const override {
fShader->emitSetupCode(g, "pts", wind.c_str());
// Visualize the input triangle as upright and equilateral, with a flat base. Paying special
// attention to wind, we can identify the points as top, bottom-left, and bottom-right.
//
// NOTE: We generate the rasters in 5 independent invocations, so each invocation designates
// the corner it will begin with as the top.
g->codeAppendf("int i = (%s > 0 ? sk_InvocationID : 4 - sk_InvocationID) %% 3;",
wind.c_str());
g->codeAppend ("float2 top = pts[i];");
g->codeAppendf("float2 right = pts[(i + (%s > 0 ? 1 : 2)) %% 3];", wind.c_str());
g->codeAppendf("float2 left = pts[(i + (%s > 0 ? 2 : 1)) %% 3];", wind.c_str());
// Determine which direction to outset the conservative raster from each of the three edges.
g->codeAppend ("float2 leftbloat = sign(top - left);");
g->codeAppend ("leftbloat = float2(0 != leftbloat.y ? leftbloat.y : leftbloat.x, "
"0 != leftbloat.x ? -leftbloat.x : -leftbloat.y);");
g->codeAppend ("float2 rightbloat = sign(right - top);");
g->codeAppend ("rightbloat = float2(0 != rightbloat.y ? rightbloat.y : rightbloat.x, "
"0 != rightbloat.x ? -rightbloat.x : -rightbloat.y);");
g->codeAppend ("float2 downbloat = sign(left - right);");
g->codeAppend ("downbloat = float2(0 != downbloat.y ? downbloat.y : downbloat.x, "
"0 != downbloat.x ? -downbloat.x : -downbloat.y);");
// The triangle's conservative raster has a coverage of +1 all around.
g->codeAppend ("half4 coverages = half4(+1);");
// Edges have coverage ramps.
g->codeAppend ("if (sk_InvocationID >= 2) {"); // Are we an edge?
Shader::CalcEdgeCoverageAtBloatVertex(g, "top", "right",
"float2(+rightbloat.y, -rightbloat.x)",
"coverages[0]");
g->codeAppend ( "coverages.yzw = half3(-1, 0, -1 - coverages[0]);");
// Reassign bloats to characterize a conservative raster around a single edge, rather than
// the entire triangle.
g->codeAppend ( "leftbloat = downbloat = -rightbloat;");
g->codeAppend ("}");
// Here we generate the conservative raster geometry. The triangle's conservative raster is
// the convex hull of 3 pixel-size boxes centered on the input points. This translates to a
// convex polygon with either one, two, or three vertices at each input point (depending on
// how sharp the corner is) that we split between two invocations. Edge conservative rasters
// are convex hulls of 2 pixel-size boxes, one at each endpoint. For more details on
// conservative raster, see:
// https://developer.nvidia.com/gpugems/GPUGems2/gpugems2_chapter42.html
g->codeAppendf("bool2 left_right_notequal = notEqual(leftbloat, rightbloat);");
g->codeAppend ("if (all(left_right_notequal)) {");
// The top corner will have three conservative raster vertices. Emit the
// middle one first to the triangle strip.
g->codeAppendf( "%s(top, float2(-leftbloat.y, +leftbloat.x), coverages[0]);",
emitVertexFn);
g->codeAppend ("}");
g->codeAppend ("if (any(left_right_notequal)) {");
// Second conservative raster vertex for the top corner.
g->codeAppendf( "%s(top, rightbloat, coverages[1]);", emitVertexFn);
g->codeAppend ("}");
// Main interior body.
g->codeAppendf("%s(top, leftbloat, coverages[2]);", emitVertexFn);
g->codeAppendf("%s(right, rightbloat, coverages[1]);", emitVertexFn);
// Here the invocations diverge slightly. We can't symmetrically divide three triangle
// points between two invocations, so each does the following:
//
// sk_InvocationID=0: Finishes the main interior body of the triangle hull.
// sk_InvocationID=1: Remaining two conservative raster vertices for the third hull corner.
// sk_InvocationID=2..4: Finish the opposite endpoint of their corresponding edge.
g->codeAppendf("bool2 right_down_notequal = notEqual(rightbloat, downbloat);");
g->codeAppend ("if (any(right_down_notequal) || 0 == sk_InvocationID) {");
g->codeAppendf( "%s((0 == sk_InvocationID) ? left : right, "
"(0 == sk_InvocationID) ? leftbloat : downbloat, "
"coverages[2]);", emitVertexFn);
g->codeAppend ("}");
g->codeAppend ("if (all(right_down_notequal) && 0 != sk_InvocationID) {");
g->codeAppendf( "%s(right, float2(-rightbloat.y, +rightbloat.x), coverages[3]);",
emitVertexFn);
g->codeAppend ("}");
// 5 invocations: 2 triangle hull invocations and 3 edges.
g->configure(InputType::kLines, OutputType::kTriangleStrip, 6, 5);
}
};
/**
* Generates a conservative raster around a convex quadrilateral that encloses a cubic or quadratic.
*/
class GrCCCoverageProcessor::GSCurveHullImpl : public GrCCCoverageProcessor::GSImpl {
public:
GSCurveHullImpl(std::unique_ptr<Shader> shader) : GSImpl(std::move(shader)) {}
void onEmitGeometryShader(const GrCCCoverageProcessor&, GrGLSLGeometryBuilder* g,
const GrShaderVar& wind, const char* emitVertexFn) const override {
const char* hullPts = "pts";
fShader->emitSetupCode(g, "pts", wind.c_str(), &hullPts);
// Visualize the input (convex) quadrilateral as a square. Paying special attention to wind,
// we can identify the points by their corresponding corner.
//
// NOTE: We split the square down the diagonal from top-right to bottom-left, and generate
// the hull in two independent invocations. Each invocation designates the corner it will
// begin with as top-left.
g->codeAppend ("int i = sk_InvocationID * 2;");
g->codeAppendf("float2 topleft = %s[i];", hullPts);
g->codeAppendf("float2 topright = %s[%s > 0 ? i + 1 : 3 - i];", hullPts, wind.c_str());
g->codeAppendf("float2 bottomleft = %s[%s > 0 ? 3 - i : i + 1];", hullPts, wind.c_str());
g->codeAppendf("float2 bottomright = %s[2 - i];", hullPts);
// Determine how much to outset the conservative raster hull from the relevant edges.
g->codeAppend ("float2 leftbloat = float2(topleft.y > bottomleft.y ? +1 : -1, "
"topleft.x > bottomleft.x ? -1 : +1);");
g->codeAppend ("float2 upbloat = float2(topright.y > topleft.y ? +1 : -1, "
"topright.x > topleft.x ? -1 : +1);");
g->codeAppend ("float2 rightbloat = float2(bottomright.y > topright.y ? +1 : -1, "
"bottomright.x > topright.x ? -1 : +1);");
// Here we generate the conservative raster geometry. It is the convex hull of 4 pixel-size
// boxes centered on the input points, split evenly between two invocations. This translates
// to a polygon with either one, two, or three vertices at each input point, depending on
// how sharp the corner is. For more details on conservative raster, see:
// https://developer.nvidia.com/gpugems/GPUGems2/gpugems2_chapter42.html
g->codeAppendf("bool2 left_up_notequal = notEqual(leftbloat, upbloat);");
g->codeAppend ("if (all(left_up_notequal)) {");
// The top-left corner will have three conservative raster vertices.
// Emit the middle one first to the triangle strip.
g->codeAppendf( "%s(topleft, float2(-leftbloat.y, leftbloat.x));", emitVertexFn);
g->codeAppend ("}");
g->codeAppend ("if (any(left_up_notequal)) {");
// Second conservative raster vertex for the top-left corner.
g->codeAppendf( "%s(topleft, leftbloat);", emitVertexFn);
g->codeAppend ("}");
// Main interior body of this invocation's half of the hull.
g->codeAppendf("%s(topleft, upbloat);", emitVertexFn);
g->codeAppendf("%s(bottomleft, leftbloat);", emitVertexFn);
g->codeAppendf("%s(topright, upbloat);", emitVertexFn);
// Remaining two conservative raster vertices for the top-right corner.
g->codeAppendf("bool2 up_right_notequal = notEqual(upbloat, rightbloat);");
g->codeAppend ("if (any(up_right_notequal)) {");
g->codeAppendf( "%s(topright, rightbloat);", emitVertexFn);
g->codeAppend ("}");
g->codeAppend ("if (all(up_right_notequal)) {");
g->codeAppendf( "%s(topright, float2(-upbloat.y, upbloat.x));", emitVertexFn);
g->codeAppend ("}");
g->configure(InputType::kLines, OutputType::kTriangleStrip, 7, 2);
}
};
/**
* Generates conservative rasters around corners (aka pixel-size boxes) and calculates
* coverage and attenuation ramps to fix up the coverage values written by the hulls.
*/
class GrCCCoverageProcessor::GSCornerImpl : public GrCCCoverageProcessor::GSImpl {
public:
GSCornerImpl(std::unique_ptr<Shader> shader) : GSImpl(std::move(shader)) {}
bool hasCoverage() const override { return true; }
void onEmitGeometryShader(const GrCCCoverageProcessor& proc, GrGLSLGeometryBuilder* g,
const GrShaderVar& wind, const char* emitVertexFn) const override {
fShader->emitSetupCode(g, "pts", wind.c_str());
g->codeAppendf("int corneridx = sk_InvocationID;");
if (!proc.isTriangles()) {
g->codeAppendf("corneridx *= %i;", proc.numInputPoints() - 1);
}
g->codeAppendf("float2 corner = pts[corneridx];");
g->codeAppendf("float2 left = pts[(corneridx + (%s > 0 ? %i : 1)) %% %i];",
wind.c_str(), proc.numInputPoints() - 1, proc.numInputPoints());
g->codeAppendf("float2 right = pts[(corneridx + (%s > 0 ? 1 : %i)) %% %i];",
wind.c_str(), proc.numInputPoints() - 1, proc.numInputPoints());
g->codeAppend ("float2 leftdir = corner - left;");
g->codeAppend ("leftdir = (float2(0) != leftdir) ? normalize(leftdir) : float2(1, 0);");
g->codeAppend ("float2 rightdir = right - corner;");
g->codeAppend ("rightdir = (float2(0) != rightdir) ? normalize(rightdir) : float2(1, 0);");
// Find "outbloat" and "crossbloat" at our corner. The outbloat points diagonally out of the
// triangle, in the direction that should ramp to zero coverage with attenuation. The
// crossbloat runs perpindicular to outbloat.
g->codeAppend ("float2 outbloat = float2(leftdir.x > rightdir.x ? +1 : -1, "
"leftdir.y > rightdir.y ? +1 : -1);");
g->codeAppend ("float2 crossbloat = float2(-outbloat.y, +outbloat.x);");
g->codeAppend ("half attenuation; {");
Shader::CalcCornerAttenuation(g, "leftdir", "rightdir", "attenuation");
g->codeAppend ("}");
if (proc.isTriangles()) {
g->codeAppend ("half2 left_coverages; {");
Shader::CalcEdgeCoveragesAtBloatVertices(g, "left", "corner", "-outbloat",
"-crossbloat", "left_coverages");
g->codeAppend ("}");
g->codeAppend ("half2 right_coverages; {");
Shader::CalcEdgeCoveragesAtBloatVertices(g, "corner", "right", "-outbloat",
"crossbloat", "right_coverages");
g->codeAppend ("}");
// Emit a corner box. The first coverage argument erases the values that were written
// previously by the hull and edge geometry. The second pair are multiplied together by
// the fragment shader. They ramp to 0 with attenuation in the direction of outbloat,
// and linearly from left-edge coverage to right-edge coverage in the direction of
// crossbloat.
//
// NOTE: Since this is not a linear mapping, it is important that the box's diagonal
// shared edge points in the direction of outbloat.
g->codeAppendf("%s(corner, -crossbloat, right_coverages[1] - left_coverages[1],"
"half2(1 + left_coverages[1], 1));",
emitVertexFn);
g->codeAppendf("%s(corner, outbloat, 1 + left_coverages[0] + right_coverages[0], "
"half2(0, attenuation));",
emitVertexFn);
g->codeAppendf("%s(corner, -outbloat, -1 - left_coverages[0] - right_coverages[0], "
"half2(1 + left_coverages[0] + right_coverages[0], 1));",
emitVertexFn);
g->codeAppendf("%s(corner, crossbloat, left_coverages[1] - right_coverages[1],"
"half2(1 + right_coverages[1], 1));",
emitVertexFn);
} else {
// Curves are simpler. The first coverage value of -1 means "wind = -wind", and causes
// the Shader to erase what it had written previously for the hull. Then, at each vertex
// of the corner box, the Shader will calculate the curve's local coverage value,
// interpolate it alongside our attenuation parameter, and multiply the two together for
// a final coverage value.
g->codeAppendf("%s(corner, -crossbloat, -1, half2(1));", emitVertexFn);
g->codeAppendf("%s(corner, outbloat, -1, half2(0, attenuation));",
emitVertexFn);
g->codeAppendf("%s(corner, -outbloat, -1, half2(1));", emitVertexFn);
g->codeAppendf("%s(corner, crossbloat, -1, half2(1));", emitVertexFn);
}
g->configure(InputType::kLines, OutputType::kTriangleStrip, 4, proc.isTriangles() ? 3 : 2);
}
};
void GrCCCoverageProcessor::initGS() {
SkASSERT(Impl::kGeometryShader == fImpl);
if (4 == this->numInputPoints() || this->hasInputWeight()) {
fVertexAttribute =
{"x_or_y_values", kFloat4_GrVertexAttribType, kFloat4_GrSLType};
GR_STATIC_ASSERT(sizeof(QuadPointInstance) ==
2 * GrVertexAttribTypeSize(kFloat4_GrVertexAttribType));
GR_STATIC_ASSERT(offsetof(QuadPointInstance, fY) ==
GrVertexAttribTypeSize(kFloat4_GrVertexAttribType));
} else {
fVertexAttribute =
{"x_or_y_values", kFloat3_GrVertexAttribType, kFloat3_GrSLType};
GR_STATIC_ASSERT(sizeof(TriPointInstance) ==
2 * GrVertexAttribTypeSize(kFloat3_GrVertexAttribType));
GR_STATIC_ASSERT(offsetof(TriPointInstance, fY) ==
GrVertexAttribTypeSize(kFloat3_GrVertexAttribType));
}
this->setVertexAttributes(&fVertexAttribute, 1);
this->setWillUseGeoShader();
}
void GrCCCoverageProcessor::appendGSMesh(sk_sp<const GrGpuBuffer> instanceBuffer, int instanceCount,
int baseInstance, SkTArray<GrMesh>* out) const {
// GSImpl doesn't actually make instanced draw calls. Instead, we feed transposed x,y point
// values to the GPU in a regular vertex array and draw kLines (see initGS). Then, each vertex
// invocation receives either the shape's x or y values as inputs, which it forwards to the
// geometry shader.
SkASSERT(Impl::kGeometryShader == fImpl);
GrMesh& mesh = out->emplace_back(GrPrimitiveType::kLines);
mesh.setNonIndexedNonInstanced(instanceCount * 2);
mesh.setVertexData(std::move(instanceBuffer), baseInstance * 2);
}
GrGLSLPrimitiveProcessor* GrCCCoverageProcessor::createGSImpl(std::unique_ptr<Shader> shadr) const {
if (GSSubpass::kHulls == fGSSubpass) {
return this->isTriangles()
? (GSImpl*) new GSTriangleHullImpl(std::move(shadr))
: (GSImpl*) new GSCurveHullImpl(std::move(shadr));
}
SkASSERT(GSSubpass::kCorners == fGSSubpass);
return new GSCornerImpl(std::move(shadr));
}