1 /*
2 * Copyright 2017 Google Inc.
3 *
4 * Use of this source code is governed by a BSD-style license that can be
5 * found in the LICENSE file.
6 */
7
8 #include "GrCCCoverageProcessor.h"
9
10 #include "GrMesh.h"
11 #include "glsl/GrGLSLVertexGeoBuilder.h"
12
13 using InputType = GrGLSLGeometryBuilder::InputType;
14 using OutputType = GrGLSLGeometryBuilder::OutputType;
15 using Shader = GrCCCoverageProcessor::Shader;
16
17 /**
18 * This class and its subclasses implement the coverage processor with geometry shaders.
19 */
20 class GrCCCoverageProcessor::GSImpl : public GrGLSLGeometryProcessor {
21 protected:
GSImpl(std::unique_ptr<Shader> shader)22 GSImpl(std::unique_ptr<Shader> shader) : fShader(std::move(shader)) {}
23
setData(const GrGLSLProgramDataManager & pdman,const GrPrimitiveProcessor &,FPCoordTransformIter && transformIter)24 void setData(const GrGLSLProgramDataManager& pdman, const GrPrimitiveProcessor&,
25 FPCoordTransformIter&& transformIter) final {
26 this->setTransformDataHelper(SkMatrix::I(), pdman, &transformIter);
27 }
28
onEmitCode(EmitArgs & args,GrGPArgs * gpArgs)29 void onEmitCode(EmitArgs& args, GrGPArgs* gpArgs) final {
30 const GrCCCoverageProcessor& proc = args.fGP.cast<GrCCCoverageProcessor>();
31
32 // The vertex shader simply forwards transposed x or y values to the geometry shader.
33 SkASSERT(1 == proc.numAttribs());
34 gpArgs->fPositionVar.set(GrVertexAttribTypeToSLType(proc.getAttrib(0).fType),
35 proc.getAttrib(0).fName);
36
37 // Geometry shader.
38 GrGLSLVaryingHandler* varyingHandler = args.fVaryingHandler;
39 this->emitGeometryShader(proc, varyingHandler, args.fGeomBuilder, args.fRTAdjustName);
40 varyingHandler->emitAttributes(proc);
41 varyingHandler->setNoPerspective();
42 SkASSERT(!args.fFPCoordTransformHandler->nextCoordTransform());
43
44 // Fragment shader.
45 fShader->emitFragmentCode(proc, args.fFragBuilder, args.fOutputColor, args.fOutputCoverage);
46 }
47
emitGeometryShader(const GrCCCoverageProcessor & proc,GrGLSLVaryingHandler * varyingHandler,GrGLSLGeometryBuilder * g,const char * rtAdjust) const48 void emitGeometryShader(const GrCCCoverageProcessor& proc,
49 GrGLSLVaryingHandler* varyingHandler, GrGLSLGeometryBuilder* g,
50 const char* rtAdjust) const {
51 int numInputPoints = proc.numInputPoints();
52 SkASSERT(3 == numInputPoints || 4 == numInputPoints);
53
54 const char* posValues = (4 == numInputPoints) ? "sk_Position" : "sk_Position.xyz";
55 g->codeAppendf("float%ix2 pts = transpose(float2x%i(sk_in[0].%s, sk_in[1].%s));",
56 numInputPoints, numInputPoints, posValues, posValues);
57
58 GrShaderVar wind("wind", kHalf_GrSLType);
59 g->declareGlobal(wind);
60 if (WindMethod::kCrossProduct == proc.fWindMethod) {
61 g->codeAppend ("float area_x2 = determinant(float2x2(pts[0] - pts[1], "
62 "pts[0] - pts[2]));");
63 if (4 == numInputPoints) {
64 g->codeAppend ("area_x2 += determinant(float2x2(pts[0] - pts[2], "
65 "pts[0] - pts[3]));");
66 }
67 g->codeAppendf("%s = sign(area_x2);", wind.c_str());
68 } else {
69 SkASSERT(WindMethod::kInstanceData == proc.fWindMethod);
70 SkASSERT(3 == numInputPoints);
71 SkASSERT(kFloat4_GrVertexAttribType == proc.getAttrib(0).fType);
72 g->codeAppendf("%s = sk_in[0].sk_Position.w;", wind.c_str());
73 }
74
75 SkString emitVertexFn;
76 SkSTArray<2, GrShaderVar> emitArgs;
77 const char* position = emitArgs.emplace_back("position", kFloat2_GrSLType).c_str();
78 const char* coverage = nullptr;
79 if (RenderPass::kTriangleEdges == proc.fRenderPass) {
80 coverage = emitArgs.emplace_back("coverage", kHalf_GrSLType).c_str();
81 }
82 g->emitFunction(kVoid_GrSLType, "emitVertex", emitArgs.count(), emitArgs.begin(), [&]() {
83 SkString fnBody;
84 fShader->emitVaryings(varyingHandler, GrGLSLVarying::Scope::kGeoToFrag, &fnBody,
85 position, coverage, wind.c_str());
86 g->emitVertex(&fnBody, position, rtAdjust);
87 return fnBody;
88 }().c_str(), &emitVertexFn);
89
90 float bloat = kAABloatRadius;
91 #ifdef SK_DEBUG
92 if (proc.debugVisualizationsEnabled()) {
93 bloat *= proc.debugBloat();
94 }
95 #endif
96 g->defineConstant("bloat", bloat);
97
98 this->onEmitGeometryShader(g, wind, emitVertexFn.c_str());
99 }
100
101 virtual void onEmitGeometryShader(GrGLSLGeometryBuilder*, const GrShaderVar& wind,
102 const char* emitVertexFn) const = 0;
103
~GSImpl()104 virtual ~GSImpl() {}
105
106 const std::unique_ptr<Shader> fShader;
107
108 typedef GrGLSLGeometryProcessor INHERITED;
109 };
110
111 /**
112 * Generates a conservative raster hull around a triangle. (See comments for RenderPass)
113 */
114 class GSHull3Impl : public GrCCCoverageProcessor::GSImpl {
115 public:
GSHull3Impl(std::unique_ptr<Shader> shader)116 GSHull3Impl(std::unique_ptr<Shader> shader) : GSImpl(std::move(shader)) {}
117
onEmitGeometryShader(GrGLSLGeometryBuilder * g,const GrShaderVar & wind,const char * emitVertexFn) const118 void onEmitGeometryShader(GrGLSLGeometryBuilder* g, const GrShaderVar& wind,
119 const char* emitVertexFn) const override {
120 Shader::GeometryVars vars;
121 fShader->emitSetupCode(g, "pts", nullptr, wind.c_str(), &vars);
122
123 const char* hullPts = vars.fHullVars.fAlternatePoints;
124 if (!hullPts) {
125 hullPts = "pts";
126 }
127
128 // Visualize the input triangle as upright and equilateral, with a flat base. Paying special
129 // attention to wind, we can identify the points as top, bottom-left, and bottom-right.
130 //
131 // NOTE: We generate the hull in 2 independent invocations, so each invocation designates
132 // the corner it will begin with as the top.
133 g->codeAppendf("int i = %s > 0 ? sk_InvocationID : 1 - sk_InvocationID;", wind.c_str());
134 g->codeAppendf("float2 top = %s[i];", hullPts);
135 g->codeAppendf("float2 left = %s[%s > 0 ? (1 - i) * 2 : i + 1];", hullPts, wind.c_str());
136 g->codeAppendf("float2 right = %s[%s > 0 ? i + 1 : (1 - i) * 2];", hullPts, wind.c_str());
137
138 // Determine how much to outset the conservative raster hull from each of the three edges.
139 g->codeAppend ("float2 leftbloat = float2(top.y > left.y ? +bloat : -bloat, "
140 "top.x > left.x ? -bloat : +bloat);");
141 g->codeAppend ("float2 rightbloat = float2(right.y > top.y ? +bloat : -bloat, "
142 "right.x > top.x ? -bloat : +bloat);");
143 g->codeAppend ("float2 downbloat = float2(left.y > right.y ? +bloat : -bloat, "
144 "left.x > right.x ? -bloat : +bloat);");
145
146 // Here we generate the conservative raster geometry. It is the convex hull of 3 pixel-size
147 // boxes centered on the input points, split between two invocations. This translates to a
148 // polygon with either one, two, or three vertices at each input point, depending on how
149 // sharp the corner is. For more details on conservative raster, see:
150 // https://developer.nvidia.com/gpugems/GPUGems2/gpugems2_chapter42.html
151 g->codeAppendf("bool2 left_right_notequal = notEqual(leftbloat, rightbloat);");
152 g->codeAppend ("if (all(left_right_notequal)) {");
153 // The top corner will have three conservative raster vertices. Emit the
154 // middle one first to the triangle strip.
155 g->codeAppendf( "%s(top + float2(-leftbloat.y, leftbloat.x));", emitVertexFn);
156 g->codeAppend ("}");
157 g->codeAppend ("if (any(left_right_notequal)) {");
158 // Second conservative raster vertex for the top corner.
159 g->codeAppendf( "%s(top + rightbloat);", emitVertexFn);
160 g->codeAppend ("}");
161
162 // Main interior body of the triangle.
163 g->codeAppendf("%s(top + leftbloat);", emitVertexFn);
164 g->codeAppendf("%s(right + rightbloat);", emitVertexFn);
165
166 // Here the two invocations diverge. We can't symmetrically divide three triangle points
167 // between two invocations, so each does the following:
168 //
169 // sk_InvocationID=0: Finishes the main interior body of the triangle.
170 // sk_InvocationID=1: Remaining two conservative raster vertices for the third corner.
171 g->codeAppendf("bool2 right_down_notequal = notEqual(rightbloat, downbloat);");
172 g->codeAppend ("if (any(right_down_notequal) || 0 == sk_InvocationID) {");
173 g->codeAppendf( "%s(sk_InvocationID == 0 ? left + leftbloat : right + downbloat);",
174 emitVertexFn);
175 g->codeAppend ("}");
176 g->codeAppend ("if (all(right_down_notequal) && 0 != sk_InvocationID) {");
177 g->codeAppendf( "%s(right + float2(-rightbloat.y, rightbloat.x));", emitVertexFn);
178 g->codeAppend ("}");
179
180 g->configure(InputType::kLines, OutputType::kTriangleStrip, 6, 2);
181 }
182 };
183
184 /**
185 * Generates a conservative raster hull around a convex quadrilateral. (See comments for RenderPass)
186 */
187 class GSHull4Impl : public GrCCCoverageProcessor::GSImpl {
188 public:
GSHull4Impl(std::unique_ptr<Shader> shader)189 GSHull4Impl(std::unique_ptr<Shader> shader) : GSImpl(std::move(shader)) {}
190
onEmitGeometryShader(GrGLSLGeometryBuilder * g,const GrShaderVar & wind,const char * emitVertexFn) const191 void onEmitGeometryShader(GrGLSLGeometryBuilder* g, const GrShaderVar& wind,
192 const char* emitVertexFn) const override {
193 Shader::GeometryVars vars;
194 fShader->emitSetupCode(g, "pts", nullptr, wind.c_str(), &vars);
195
196 const char* hullPts = vars.fHullVars.fAlternatePoints;
197 if (!hullPts) {
198 hullPts = "pts";
199 }
200
201 // Visualize the input (convex) quadrilateral as a square. Paying special attention to wind,
202 // we can identify the points by their corresponding corner.
203 //
204 // NOTE: We split the square down the diagonal from top-right to bottom-left, and generate
205 // the hull in two independent invocations. Each invocation designates the corner it will
206 // begin with as top-left.
207 g->codeAppend ("int i = sk_InvocationID * 2;");
208 g->codeAppendf("float2 topleft = %s[i];", hullPts);
209 g->codeAppendf("float2 topright = %s[%s > 0 ? i + 1 : 3 - i];", hullPts, wind.c_str());
210 g->codeAppendf("float2 bottomleft = %s[%s > 0 ? 3 - i : i + 1];", hullPts, wind.c_str());
211 g->codeAppendf("float2 bottomright = %s[2 - i];", hullPts);
212
213 // Determine how much to outset the conservative raster hull from the relevant edges.
214 g->codeAppend ("float2 leftbloat = float2(topleft.y > bottomleft.y ? +bloat : -bloat, "
215 "topleft.x > bottomleft.x ? -bloat : bloat);");
216 g->codeAppend ("float2 upbloat = float2(topright.y > topleft.y ? +bloat : -bloat, "
217 "topright.x > topleft.x ? -bloat : +bloat);");
218 g->codeAppend ("float2 rightbloat = float2(bottomright.y > topright.y ? +bloat : -bloat, "
219 "bottomright.x > topright.x ? -bloat : +bloat);");
220
221 // Here we generate the conservative raster geometry. It is the convex hull of 4 pixel-size
222 // boxes centered on the input points, split evenly between two invocations. This translates
223 // to a polygon with either one, two, or three vertices at each input point, depending on
224 // how sharp the corner is. For more details on conservative raster, see:
225 // https://developer.nvidia.com/gpugems/GPUGems2/gpugems2_chapter42.html
226 g->codeAppendf("bool2 left_up_notequal = notEqual(leftbloat, upbloat);");
227 g->codeAppend ("if (all(left_up_notequal)) {");
228 // The top-left corner will have three conservative raster vertices.
229 // Emit the middle one first to the triangle strip.
230 g->codeAppendf( "%s(topleft + float2(-leftbloat.y, leftbloat.x));", emitVertexFn);
231 g->codeAppend ("}");
232 g->codeAppend ("if (any(left_up_notequal)) {");
233 // Second conservative raster vertex for the top-left corner.
234 g->codeAppendf( "%s(topleft + leftbloat);", emitVertexFn);
235 g->codeAppend ("}");
236
237 // Main interior body of this invocation's half of the hull.
238 g->codeAppendf("%s(topleft + upbloat);", emitVertexFn);
239 g->codeAppendf("%s(bottomleft + leftbloat);", emitVertexFn);
240 g->codeAppendf("%s(topright + upbloat);", emitVertexFn);
241
242 // Remaining two conservative raster vertices for the top-right corner.
243 g->codeAppendf("bool2 up_right_notequal = notEqual(upbloat, rightbloat);");
244 g->codeAppend ("if (any(up_right_notequal)) {");
245 g->codeAppendf( "%s(topright + rightbloat);", emitVertexFn);
246 g->codeAppend ("}");
247 g->codeAppend ("if (all(up_right_notequal)) {");
248 g->codeAppendf( "%s(topright + float2(-upbloat.y, upbloat.x));", emitVertexFn);
249 g->codeAppend ("}");
250
251 g->configure(InputType::kLines, OutputType::kTriangleStrip, 7, 2);
252 }
253 };
254
255 /**
256 * Generates conservatives around each edge of a triangle. (See comments for RenderPass)
257 */
258 class GSEdgeImpl : public GrCCCoverageProcessor::GSImpl {
259 public:
GSEdgeImpl(std::unique_ptr<Shader> shader)260 GSEdgeImpl(std::unique_ptr<Shader> shader) : GSImpl(std::move(shader)) {}
261
onEmitGeometryShader(GrGLSLGeometryBuilder * g,const GrShaderVar & wind,const char * emitVertexFn) const262 void onEmitGeometryShader(GrGLSLGeometryBuilder* g, const GrShaderVar& wind,
263 const char* emitVertexFn) const override {
264 fShader->emitSetupCode(g, "pts", "sk_InvocationID", wind.c_str(), nullptr);
265
266 g->codeAppend ("int nextidx = 2 != sk_InvocationID ? sk_InvocationID + 1 : 0;");
267 g->codeAppendf("float2 left = pts[%s > 0 ? sk_InvocationID : nextidx];", wind.c_str());
268 g->codeAppendf("float2 right = pts[%s > 0 ? nextidx : sk_InvocationID];", wind.c_str());
269
270 Shader::EmitEdgeDistanceEquation(g, "left", "right", "float3 edge_distance_equation");
271
272 // Which quadrant does the vector from left -> right fall into?
273 g->codeAppend ("float2 qlr = sign(right - left);");
274 g->codeAppend ("float2x2 outer_pts = float2x2(left - bloat * qlr, right + bloat * qlr);");
275 g->codeAppend ("half2 outer_coverage = edge_distance_equation.xy * outer_pts + "
276 "edge_distance_equation.z;");
277
278 g->codeAppend ("float2 d1 = float2(qlr.y, -qlr.x);");
279 g->codeAppend ("float2 d2 = d1;");
280 g->codeAppend ("bool aligned = qlr.x == 0 || qlr.y == 0;");
281 g->codeAppend ("if (aligned) {");
282 g->codeAppend ( "d1 -= qlr;");
283 g->codeAppend ( "d2 += qlr;");
284 g->codeAppend ("}");
285
286 // Emit the convex hull of 2 pixel-size boxes centered on the endpoints of the edge. Each
287 // invocation emits a different edge. Emit negative coverage that subtracts the appropiate
288 // amount back out from the hull we drew above.
289 g->codeAppend ("if (!aligned) {");
290 g->codeAppendf( "%s(outer_pts[0], outer_coverage[0]);", emitVertexFn);
291 g->codeAppend ("}");
292 g->codeAppendf("%s(left + bloat * d1, -1);", emitVertexFn);
293 g->codeAppendf("%s(left - bloat * d2, 0);", emitVertexFn);
294 g->codeAppendf("%s(right + bloat * d2, -1);", emitVertexFn);
295 g->codeAppendf("%s(right - bloat * d1, 0);", emitVertexFn);
296 g->codeAppend ("if (!aligned) {");
297 g->codeAppendf( "%s(outer_pts[1], outer_coverage[1]);", emitVertexFn);
298 g->codeAppend ("}");
299
300 g->configure(InputType::kLines, OutputType::kTriangleStrip, 6, 3);
301 }
302 };
303
304 /**
305 * Generates conservative rasters around corners. (See comments for RenderPass)
306 */
307 class GSCornerImpl : public GrCCCoverageProcessor::GSImpl {
308 public:
GSCornerImpl(std::unique_ptr<Shader> shader,int numCorners)309 GSCornerImpl(std::unique_ptr<Shader> shader, int numCorners)
310 : GSImpl(std::move(shader)), fNumCorners(numCorners) {}
311
onEmitGeometryShader(GrGLSLGeometryBuilder * g,const GrShaderVar & wind,const char * emitVertexFn) const312 void onEmitGeometryShader(GrGLSLGeometryBuilder* g, const GrShaderVar& wind,
313 const char* emitVertexFn) const override {
314 Shader::GeometryVars vars;
315 fShader->emitSetupCode(g, "pts", "sk_InvocationID", wind.c_str(), &vars);
316
317 const char* corner = vars.fCornerVars.fPoint;
318 SkASSERT(corner);
319
320 g->codeAppendf("%s(%s + float2(-bloat, -bloat));", emitVertexFn, corner);
321 g->codeAppendf("%s(%s + float2(-bloat, +bloat));", emitVertexFn, corner);
322 g->codeAppendf("%s(%s + float2(+bloat, -bloat));", emitVertexFn, corner);
323 g->codeAppendf("%s(%s + float2(+bloat, +bloat));", emitVertexFn, corner);
324
325 g->configure(InputType::kLines, OutputType::kTriangleStrip, 4, fNumCorners);
326 }
327
328 private:
329 const int fNumCorners;
330 };
331
initGS()332 void GrCCCoverageProcessor::initGS() {
333 SkASSERT(Impl::kGeometryShader == fImpl);
334 if (RenderPassIsCubic(fRenderPass) || WindMethod::kInstanceData == fWindMethod) {
335 SkASSERT(WindMethod::kCrossProduct == fWindMethod || 3 == this->numInputPoints());
336 this->addVertexAttrib("x_or_y_values", kFloat4_GrVertexAttribType);
337 SkASSERT(sizeof(QuadPointInstance) == this->getVertexStride() * 2);
338 SkASSERT(offsetof(QuadPointInstance, fY) == this->getVertexStride());
339 GR_STATIC_ASSERT(0 == offsetof(QuadPointInstance, fX));
340 } else {
341 this->addVertexAttrib("x_or_y_values", kFloat3_GrVertexAttribType);
342 SkASSERT(sizeof(TriPointInstance) == this->getVertexStride() * 2);
343 SkASSERT(offsetof(TriPointInstance, fY) == this->getVertexStride());
344 GR_STATIC_ASSERT(0 == offsetof(TriPointInstance, fX));
345 }
346 this->setWillUseGeoShader();
347 }
348
appendGSMesh(GrBuffer * instanceBuffer,int instanceCount,int baseInstance,SkTArray<GrMesh> * out) const349 void GrCCCoverageProcessor::appendGSMesh(GrBuffer* instanceBuffer, int instanceCount,
350 int baseInstance, SkTArray<GrMesh>* out) const {
351 // GSImpl doesn't actually make instanced draw calls. Instead, we feed transposed x,y point
352 // values to the GPU in a regular vertex array and draw kLines (see initGS). Then, each vertex
353 // invocation receives either the shape's x or y values as inputs, which it forwards to the
354 // geometry shader.
355 SkASSERT(Impl::kGeometryShader == fImpl);
356 GrMesh& mesh = out->emplace_back(GrPrimitiveType::kLines);
357 mesh.setNonIndexedNonInstanced(instanceCount * 2);
358 mesh.setVertexData(instanceBuffer, baseInstance * 2);
359 }
360
createGSImpl(std::unique_ptr<Shader> shadr) const361 GrGLSLPrimitiveProcessor* GrCCCoverageProcessor::createGSImpl(std::unique_ptr<Shader> shadr) const {
362 switch (fRenderPass) {
363 case RenderPass::kTriangleHulls:
364 return new GSHull3Impl(std::move(shadr));
365 case RenderPass::kQuadraticHulls:
366 case RenderPass::kCubicHulls:
367 return new GSHull4Impl(std::move(shadr));
368 case RenderPass::kTriangleEdges:
369 return new GSEdgeImpl(std::move(shadr));
370 case RenderPass::kTriangleCorners:
371 return new GSCornerImpl(std::move(shadr), 3);
372 case RenderPass::kQuadraticCorners:
373 case RenderPass::kCubicCorners:
374 return new GSCornerImpl(std::move(shadr), 2);
375 }
376 SK_ABORT("Invalid RenderPass");
377 return nullptr;
378 }
379