/*
* 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;
using Shader = GrCCCoverageProcessor::Shader;
/**
* 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)) {}
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.numAttribs());
gpArgs->fPositionVar.set(GrVertexAttribTypeToSLType(proc.getAttrib(0).fType),
proc.getAttrib(0).fName);
// 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);
const char* posValues = (4 == numInputPoints) ? "sk_Position" : "sk_Position.xyz";
g->codeAppendf("float%ix2 pts = transpose(float2x%i(sk_in[0].%s, sk_in[1].%s));",
numInputPoints, numInputPoints, posValues, posValues);
GrShaderVar wind("wind", kHalf_GrSLType);
g->declareGlobal(wind);
if (WindMethod::kCrossProduct == proc.fWindMethod) {
g->codeAppend ("float area_x2 = determinant(float2x2(pts[0] - pts[1], "
"pts[0] - pts[2]));");
if (4 == numInputPoints) {
g->codeAppend ("area_x2 += determinant(float2x2(pts[0] - pts[2], "
"pts[0] - pts[3]));");
}
g->codeAppendf("%s = sign(area_x2);", wind.c_str());
} else {
SkASSERT(WindMethod::kInstanceData == proc.fWindMethod);
SkASSERT(3 == numInputPoints);
SkASSERT(kFloat4_GrVertexAttribType == proc.getAttrib(0).fType);
g->codeAppendf("%s = sk_in[0].sk_Position.w;", wind.c_str());
}
SkString emitVertexFn;
SkSTArray<2, GrShaderVar> emitArgs;
const char* position = emitArgs.emplace_back("position", kFloat2_GrSLType).c_str();
const char* coverage = nullptr;
if (RenderPass::kTriangleEdges == proc.fRenderPass) {
coverage = emitArgs.emplace_back("coverage", kHalf_GrSLType).c_str();
}
g->emitFunction(kVoid_GrSLType, "emitVertex", emitArgs.count(), emitArgs.begin(), [&]() {
SkString fnBody;
fShader->emitVaryings(varyingHandler, GrGLSLVarying::Scope::kGeoToFrag, &fnBody,
position, coverage, wind.c_str());
g->emitVertex(&fnBody, position, rtAdjust);
return fnBody;
}().c_str(), &emitVertexFn);
float bloat = kAABloatRadius;
#ifdef SK_DEBUG
if (proc.debugVisualizationsEnabled()) {
bloat *= proc.debugBloat();
}
#endif
g->defineConstant("bloat", bloat);
this->onEmitGeometryShader(g, wind, emitVertexFn.c_str());
}
virtual void onEmitGeometryShader(GrGLSLGeometryBuilder*, const GrShaderVar& wind,
const char* emitVertexFn) const = 0;
virtual ~GSImpl() {}
const std::unique_ptr<Shader> fShader;
typedef GrGLSLGeometryProcessor INHERITED;
};
/**
* Generates a conservative raster hull around a triangle. (See comments for RenderPass)
*/
class GSHull3Impl : public GrCCCoverageProcessor::GSImpl {
public:
GSHull3Impl(std::unique_ptr<Shader> shader) : GSImpl(std::move(shader)) {}
void onEmitGeometryShader(GrGLSLGeometryBuilder* g, const GrShaderVar& wind,
const char* emitVertexFn) const override {
Shader::GeometryVars vars;
fShader->emitSetupCode(g, "pts", nullptr, wind.c_str(), &vars);
const char* hullPts = vars.fHullVars.fAlternatePoints;
if (!hullPts) {
hullPts = "pts";
}
// 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 hull in 2 independent invocations, so each invocation designates
// the corner it will begin with as the top.
g->codeAppendf("int i = %s > 0 ? sk_InvocationID : 1 - sk_InvocationID;", wind.c_str());
g->codeAppendf("float2 top = %s[i];", hullPts);
g->codeAppendf("float2 left = %s[%s > 0 ? (1 - i) * 2 : i + 1];", hullPts, wind.c_str());
g->codeAppendf("float2 right = %s[%s > 0 ? i + 1 : (1 - i) * 2];", hullPts, wind.c_str());
// Determine how much to outset the conservative raster hull from each of the three edges.
g->codeAppend ("float2 leftbloat = float2(top.y > left.y ? +bloat : -bloat, "
"top.x > left.x ? -bloat : +bloat);");
g->codeAppend ("float2 rightbloat = float2(right.y > top.y ? +bloat : -bloat, "
"right.x > top.x ? -bloat : +bloat);");
g->codeAppend ("float2 downbloat = float2(left.y > right.y ? +bloat : -bloat, "
"left.x > right.x ? -bloat : +bloat);");
// Here we generate the conservative raster geometry. It is the convex hull of 3 pixel-size
// boxes centered on the input points, split 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_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));", emitVertexFn);
g->codeAppend ("}");
g->codeAppend ("if (any(left_right_notequal)) {");
// Second conservative raster vertex for the top corner.
g->codeAppendf( "%s(top + rightbloat);", emitVertexFn);
g->codeAppend ("}");
// Main interior body of the triangle.
g->codeAppendf("%s(top + leftbloat);", emitVertexFn);
g->codeAppendf("%s(right + rightbloat);", emitVertexFn);
// Here the two invocations diverge. 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.
// sk_InvocationID=1: Remaining two conservative raster vertices for the third corner.
g->codeAppendf("bool2 right_down_notequal = notEqual(rightbloat, downbloat);");
g->codeAppend ("if (any(right_down_notequal) || 0 == sk_InvocationID) {");
g->codeAppendf( "%s(sk_InvocationID == 0 ? left + leftbloat : right + downbloat);",
emitVertexFn);
g->codeAppend ("}");
g->codeAppend ("if (all(right_down_notequal) && 0 != sk_InvocationID) {");
g->codeAppendf( "%s(right + float2(-rightbloat.y, rightbloat.x));", emitVertexFn);
g->codeAppend ("}");
g->configure(InputType::kLines, OutputType::kTriangleStrip, 6, 2);
}
};
/**
* Generates a conservative raster hull around a convex quadrilateral. (See comments for RenderPass)
*/
class GSHull4Impl : public GrCCCoverageProcessor::GSImpl {
public:
GSHull4Impl(std::unique_ptr<Shader> shader) : GSImpl(std::move(shader)) {}
void onEmitGeometryShader(GrGLSLGeometryBuilder* g, const GrShaderVar& wind,
const char* emitVertexFn) const override {
Shader::GeometryVars vars;
fShader->emitSetupCode(g, "pts", nullptr, wind.c_str(), &vars);
const char* hullPts = vars.fHullVars.fAlternatePoints;
if (!hullPts) {
hullPts = "pts";
}
// 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 ? +bloat : -bloat, "
"topleft.x > bottomleft.x ? -bloat : bloat);");
g->codeAppend ("float2 upbloat = float2(topright.y > topleft.y ? +bloat : -bloat, "
"topright.x > topleft.x ? -bloat : +bloat);");
g->codeAppend ("float2 rightbloat = float2(bottomright.y > topright.y ? +bloat : -bloat, "
"bottomright.x > topright.x ? -bloat : +bloat);");
// 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 conservatives around each edge of a triangle. (See comments for RenderPass)
*/
class GSEdgeImpl : public GrCCCoverageProcessor::GSImpl {
public:
GSEdgeImpl(std::unique_ptr<Shader> shader) : GSImpl(std::move(shader)) {}
void onEmitGeometryShader(GrGLSLGeometryBuilder* g, const GrShaderVar& wind,
const char* emitVertexFn) const override {
fShader->emitSetupCode(g, "pts", "sk_InvocationID", wind.c_str(), nullptr);
g->codeAppend ("int nextidx = 2 != sk_InvocationID ? sk_InvocationID + 1 : 0;");
g->codeAppendf("float2 left = pts[%s > 0 ? sk_InvocationID : nextidx];", wind.c_str());
g->codeAppendf("float2 right = pts[%s > 0 ? nextidx : sk_InvocationID];", wind.c_str());
Shader::EmitEdgeDistanceEquation(g, "left", "right", "float3 edge_distance_equation");
// Which quadrant does the vector from left -> right fall into?
g->codeAppend ("float2 qlr = sign(right - left);");
g->codeAppend ("float2x2 outer_pts = float2x2(left - bloat * qlr, right + bloat * qlr);");
g->codeAppend ("half2 outer_coverage = edge_distance_equation.xy * outer_pts + "
"edge_distance_equation.z;");
g->codeAppend ("float2 d1 = float2(qlr.y, -qlr.x);");
g->codeAppend ("float2 d2 = d1;");
g->codeAppend ("bool aligned = qlr.x == 0 || qlr.y == 0;");
g->codeAppend ("if (aligned) {");
g->codeAppend ( "d1 -= qlr;");
g->codeAppend ( "d2 += qlr;");
g->codeAppend ("}");
// Emit the convex hull of 2 pixel-size boxes centered on the endpoints of the edge. Each
// invocation emits a different edge. Emit negative coverage that subtracts the appropiate
// amount back out from the hull we drew above.
g->codeAppend ("if (!aligned) {");
g->codeAppendf( "%s(outer_pts[0], outer_coverage[0]);", emitVertexFn);
g->codeAppend ("}");
g->codeAppendf("%s(left + bloat * d1, -1);", emitVertexFn);
g->codeAppendf("%s(left - bloat * d2, 0);", emitVertexFn);
g->codeAppendf("%s(right + bloat * d2, -1);", emitVertexFn);
g->codeAppendf("%s(right - bloat * d1, 0);", emitVertexFn);
g->codeAppend ("if (!aligned) {");
g->codeAppendf( "%s(outer_pts[1], outer_coverage[1]);", emitVertexFn);
g->codeAppend ("}");
g->configure(InputType::kLines, OutputType::kTriangleStrip, 6, 3);
}
};
/**
* Generates conservative rasters around corners. (See comments for RenderPass)
*/
class GSCornerImpl : public GrCCCoverageProcessor::GSImpl {
public:
GSCornerImpl(std::unique_ptr<Shader> shader, int numCorners)
: GSImpl(std::move(shader)), fNumCorners(numCorners) {}
void onEmitGeometryShader(GrGLSLGeometryBuilder* g, const GrShaderVar& wind,
const char* emitVertexFn) const override {
Shader::GeometryVars vars;
fShader->emitSetupCode(g, "pts", "sk_InvocationID", wind.c_str(), &vars);
const char* corner = vars.fCornerVars.fPoint;
SkASSERT(corner);
g->codeAppendf("%s(%s + float2(-bloat, -bloat));", emitVertexFn, corner);
g->codeAppendf("%s(%s + float2(-bloat, +bloat));", emitVertexFn, corner);
g->codeAppendf("%s(%s + float2(+bloat, -bloat));", emitVertexFn, corner);
g->codeAppendf("%s(%s + float2(+bloat, +bloat));", emitVertexFn, corner);
g->configure(InputType::kLines, OutputType::kTriangleStrip, 4, fNumCorners);
}
private:
const int fNumCorners;
};
void GrCCCoverageProcessor::initGS() {
SkASSERT(Impl::kGeometryShader == fImpl);
if (RenderPassIsCubic(fRenderPass) || WindMethod::kInstanceData == fWindMethod) {
SkASSERT(WindMethod::kCrossProduct == fWindMethod || 3 == this->numInputPoints());
this->addVertexAttrib("x_or_y_values", kFloat4_GrVertexAttribType);
SkASSERT(sizeof(QuadPointInstance) == this->getVertexStride() * 2);
SkASSERT(offsetof(QuadPointInstance, fY) == this->getVertexStride());
GR_STATIC_ASSERT(0 == offsetof(QuadPointInstance, fX));
} else {
this->addVertexAttrib("x_or_y_values", kFloat3_GrVertexAttribType);
SkASSERT(sizeof(TriPointInstance) == this->getVertexStride() * 2);
SkASSERT(offsetof(TriPointInstance, fY) == this->getVertexStride());
GR_STATIC_ASSERT(0 == offsetof(TriPointInstance, fX));
}
this->setWillUseGeoShader();
}
void GrCCCoverageProcessor::appendGSMesh(GrBuffer* 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(instanceBuffer, baseInstance * 2);
}
GrGLSLPrimitiveProcessor* GrCCCoverageProcessor::createGSImpl(std::unique_ptr<Shader> shadr) const {
switch (fRenderPass) {
case RenderPass::kTriangleHulls:
return new GSHull3Impl(std::move(shadr));
case RenderPass::kQuadraticHulls:
case RenderPass::kCubicHulls:
return new GSHull4Impl(std::move(shadr));
case RenderPass::kTriangleEdges:
return new GSEdgeImpl(std::move(shadr));
case RenderPass::kTriangleCorners:
return new GSCornerImpl(std::move(shadr), 3);
case RenderPass::kQuadraticCorners:
case RenderPass::kCubicCorners:
return new GSCornerImpl(std::move(shadr), 2);
}
SK_ABORT("Invalid RenderPass");
return nullptr;
}