/* * 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) : 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(); // 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 *= 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 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) : 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) : 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) : 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 instanceBuffer, int instanceCount, int baseInstance, SkTArray* 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 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)); }