| /* |
| * Copyright 2020 Google LLC. |
| * |
| * Use of this source code is governed by a BSD-style license that can be |
| * found in the LICENSE file. |
| */ |
| |
| #include "src/gpu/tessellate/GrStrokeTessellateShader.h" |
| |
| #include "src/gpu/glsl/GrGLSLFragmentShaderBuilder.h" |
| #include "src/gpu/glsl/GrGLSLGeometryProcessor.h" |
| #include "src/gpu/glsl/GrGLSLVarying.h" |
| #include "src/gpu/glsl/GrGLSLVertexGeoBuilder.h" |
| #include "src/gpu/tessellate/GrStrokeTessellator.h" |
| #include "src/gpu/tessellate/GrWangsFormula.h" |
| |
| // The built-in atan() is undefined when x==0. This method relieves that restriction, but also can |
| // return values larger than 2*PI. This shouldn't matter for our purposes. |
| static const char* kAtan2Fn = R"( |
| float atan2(float2 v) { |
| float bias = 0.0; |
| if (abs(v.y) > abs(v.x)) { |
| v = float2(v.y, -v.x); |
| bias = PI/2.0; |
| } |
| return atan(v.y, v.x) + bias; |
| })"; |
| |
| static const char* kCosineBetweenVectorsFn = R"( |
| float cosine_between_vectors(float2 a, float2 b) { |
| float ab_cosTheta = dot(a,b); |
| float ab_pow2 = dot(a,a) * dot(b,b); |
| return (ab_pow2 == 0.0) ? 1.0 : clamp(ab_cosTheta * inversesqrt(ab_pow2), -1.0, 1.0); |
| })"; |
| |
| // Extends the middle radius to either the miter point, or the bevel edge if we surpassed the miter |
| // limit and need to revert to a bevel join. |
| static const char* kMiterExtentFn = R"( |
| float miter_extent(float cosTheta, float miterLimit) { |
| float x = fma(cosTheta, .5, .5); |
| return (x * miterLimit * miterLimit >= 1.0) ? inversesqrt(x) : sqrt(x); |
| })"; |
| |
| static const char* kLengthPow2Fn = R"( |
| float length_pow2(float2 v) { |
| return dot(v, v); |
| })"; |
| |
| static const char* kNumRadialSegmentsPerRadian = R"( |
| float num_radial_segments_per_radian(float parametricIntolerance, float strokeRadius) { |
| return .5 / acos(max(1.0 - 1.0/(parametricIntolerance * strokeRadius), -1.0)); |
| })"; |
| |
| // Unlike mix(), this does not return b when t==1. But it otherwise seems to get better |
| // precision than "a*(1 - t) + b*t" for things like chopping cubics on exact cusp points. |
| // We override this result anyway when t==1 so it shouldn't be a problem. |
| static const char* kUncheckedMixFn = R"( |
| float unchecked_mix(float a, float b, float T) { |
| return fma(b - a, T, a); |
| } |
| float2 unchecked_mix(float2 a, float2 b, float T) { |
| return fma(b - a, float2(T), a); |
| } |
| float4 unchecked_mix(float4 a, float4 b, float4 T) { |
| return fma(b - a, T, a); |
| })"; |
| |
| // Calculates the number of evenly spaced (in the parametric sense) segments to chop a cubic into. |
| // (See GrWangsFormula::cubic() for more documentation on this formula.) The final tessellated strip |
| // will be a composition of these parametric segments as well as radial segments. |
| static void append_wangs_formula_fn(SkString* code, bool hasConics) { |
| code->appendf(R"( |
| float wangs_formula(in float4x2 P, in float w, in float parametricIntolerance) { |
| const float CUBIC_TERM_POW2 = %f; |
| float l0 = length_pow2(fma(float2(-2), P[1], P[2]) + P[0]); |
| float l1 = length_pow2(fma(float2(-2), P[2], P[3]) + P[1]); |
| float m = CUBIC_TERM_POW2 * max(l0, l1);)", GrWangsFormula::length_term_pow2<3>(1)); |
| if (hasConics) { |
| code->appendf(R"( |
| const float QUAD_TERM_POW2 = %f; |
| m = (w > 0.0) ? QUAD_TERM_POW2 * l0 : m;)", GrWangsFormula::length_term_pow2<2>(1)); |
| } |
| code->append(R"( |
| return max(ceil(sqrt(parametricIntolerance * sqrt(m))), 1.0); |
| })"); |
| } |
| |
| class GrStrokeTessellateShader::TessellationImpl : public GrGLSLGeometryProcessor { |
| public: |
| const char* getTessArgsUniformName(const GrGLSLUniformHandler& uniformHandler) const { |
| return uniformHandler.getUniformCStr(fTessArgsUniform); |
| } |
| const char* getTranslateUniformName(const GrGLSLUniformHandler& uniformHandler) const { |
| return uniformHandler.getUniformCStr(fTranslateUniform); |
| } |
| const char* getAffineMatrixUniformName(const GrGLSLUniformHandler& uniformHandler) const { |
| return uniformHandler.getUniformCStr(fAffineMatrixUniform); |
| } |
| |
| private: |
| void onEmitCode(EmitArgs& args, GrGPArgs* gpArgs) override { |
| const auto& shader = args.fGeomProc.cast<GrStrokeTessellateShader>(); |
| auto* uniHandler = args.fUniformHandler; |
| auto* v = args.fVertBuilder; |
| |
| args.fVaryingHandler->emitAttributes(shader); |
| |
| v->defineConstant("float", "PI", "3.141592653589793238"); |
| |
| // The vertex shader chops the curve into 3 sections in order to meet our tessellation |
| // requirements. The stroke tessellator does not allow curve sections to inflect or to |
| // rotate more than 180 degrees. |
| // |
| // We start by chopping at inflections (if the curve has any), or else at midtangent. If we |
| // still don't have 3 sections after that then we just subdivide uniformly in parametric |
| // space. |
| using TypeModifier = GrShaderVar::TypeModifier; |
| v->defineConstantf("float", "kParametricEpsilon", "1.0 / (%i * 128)", |
| args.fShaderCaps->maxTessellationSegments()); // 1/128 of a segment. |
| |
| // [numSegmentsInJoin, innerJoinRadiusMultiplier, prevJoinTangent.xy] |
| v->declareGlobal(GrShaderVar("vsJoinArgs0", kFloat4_GrSLType, TypeModifier::Out)); |
| |
| // [joinAngle0, radsPerJoinSegment, joinOutsetClamp.xy] |
| v->declareGlobal(GrShaderVar("vsJoinArgs1", kFloat4_GrSLType, TypeModifier::Out)); |
| |
| // Curve args. |
| v->declareGlobal(GrShaderVar("vsPts01", kFloat4_GrSLType, TypeModifier::Out)); |
| v->declareGlobal(GrShaderVar("vsPts23", kFloat4_GrSLType, TypeModifier::Out)); |
| v->declareGlobal(GrShaderVar("vsPts45", kFloat4_GrSLType, TypeModifier::Out)); |
| v->declareGlobal(GrShaderVar("vsPts67", kFloat4_GrSLType, TypeModifier::Out)); |
| v->declareGlobal(GrShaderVar("vsPts89", kFloat4_GrSLType, TypeModifier::Out)); |
| v->declareGlobal(GrShaderVar("vsTans01", kFloat4_GrSLType, TypeModifier::Out)); |
| v->declareGlobal(GrShaderVar("vsTans23", kFloat4_GrSLType, TypeModifier::Out)); |
| if (shader.hasDynamicStroke()) { |
| // [NUM_RADIAL_SEGMENTS_PER_RADIAN, STROKE_RADIUS] |
| v->declareGlobal(GrShaderVar("vsStrokeArgs", kFloat2_GrSLType, TypeModifier::Out)); |
| } |
| if (shader.hasDynamicColor()) { |
| v->declareGlobal(GrShaderVar("vsColor", kHalf4_GrSLType, TypeModifier::Out)); |
| } |
| |
| v->insertFunction(kAtan2Fn); |
| v->insertFunction(kCosineBetweenVectorsFn); |
| v->insertFunction(kMiterExtentFn); |
| v->insertFunction(kUncheckedMixFn); |
| v->insertFunction(kLengthPow2Fn); |
| if (shader.hasDynamicStroke()) { |
| v->insertFunction(kNumRadialSegmentsPerRadian); |
| } |
| |
| if (!shader.hasDynamicStroke()) { |
| // [PARAMETRIC_INTOLERANCE, NUM_RADIAL_SEGMENTS_PER_RADIAN, JOIN_TYPE, STROKE_RADIUS] |
| const char* tessArgsName; |
| fTessArgsUniform = uniHandler->addUniform(nullptr, |
| kVertex_GrShaderFlag | |
| kTessControl_GrShaderFlag | |
| kTessEvaluation_GrShaderFlag, |
| kFloat4_GrSLType, "tessArgs", &tessArgsName); |
| v->codeAppendf(R"( |
| float NUM_RADIAL_SEGMENTS_PER_RADIAN = %s.y; |
| float JOIN_TYPE = %s.z;)", tessArgsName, tessArgsName); |
| } else { |
| const char* parametricIntoleranceName; |
| fTessArgsUniform = uniHandler->addUniform(nullptr, |
| kVertex_GrShaderFlag | |
| kTessControl_GrShaderFlag | |
| kTessEvaluation_GrShaderFlag, |
| kFloat_GrSLType, "parametricIntolerance", |
| ¶metricIntoleranceName); |
| v->codeAppendf(R"( |
| float STROKE_RADIUS = dynamicStrokeAttr.x; |
| float NUM_RADIAL_SEGMENTS_PER_RADIAN = num_radial_segments_per_radian(%s,STROKE_RADIUS); |
| float JOIN_TYPE = dynamicStrokeAttr.y;)", parametricIntoleranceName); |
| } |
| |
| if (!shader.viewMatrix().isIdentity()) { |
| fTranslateUniform = uniHandler->addUniform(nullptr, kTessEvaluation_GrShaderFlag, |
| kFloat2_GrSLType, "translate", nullptr); |
| const char* affineMatrixName; |
| // Hairlines apply the affine matrix in their vertex shader, prior to tessellation. |
| // Otherwise the entire view matrix gets applied at the end of the tess eval shader. |
| auto affineMatrixVisibility = (shader.fStroke.isHairlineStyle()) ? |
| kVertex_GrShaderFlag : kTessEvaluation_GrShaderFlag; |
| fAffineMatrixUniform = uniHandler->addUniform(nullptr, affineMatrixVisibility, |
| kFloat4_GrSLType, "affineMatrix", |
| &affineMatrixName); |
| if (affineMatrixVisibility & kVertex_GrShaderFlag) { |
| v->codeAppendf("float2x2 AFFINE_MATRIX = float2x2(%s);\n", affineMatrixName); |
| } |
| } |
| |
| v->codeAppend(R"( |
| // Unpack the control points. |
| float2 prevControlPoint = prevCtrlPtAttr; |
| float4x2 P = float4x2(pts01Attr, pts23Attr);)"); |
| |
| if (shader.fStroke.isHairlineStyle() && !shader.viewMatrix().isIdentity()) { |
| // Hairline case. Transform the points before tessellation. We can still hold off on the |
| // translate until the end; we just need to perform the scale and skew right now. |
| if (shader.hasConics()) { |
| v->codeAppend(R"( |
| P[0] = AFFINE_MATRIX * P[0]; |
| P[1] = AFFINE_MATRIX * P[1]; |
| P[2] = AFFINE_MATRIX * P[2]; |
| P[3] = isinf(P[3].y) ? P[3] : AFFINE_MATRIX * P[3];)"); |
| } else { |
| v->codeAppend(R"( |
| P = AFFINE_MATRIX * P;)"); |
| } |
| v->codeAppend(R"( |
| prevControlPoint = AFFINE_MATRIX * prevControlPoint;)"); |
| } |
| |
| v->codeAppend(R"( |
| // Find the tangents. It's imperative that we compute these tangents from the original |
| // (pre-chopping) input points or else the seams might crack. |
| float2 prevJoinTangent = P[0] - prevControlPoint; |
| float2 tan0 = ((P[1] == P[0]) ? P[2] : P[1]) - P[0]; |
| float2 tan1 = (P[3] == P[2] || isinf(P[3].y)) ? P[2] - P[1] : P[3] - P[2]; |
| |
| if (tan0 == float2(0)) { |
| // [p0, p0, p0, p3] is a reserved pattern that means this patch is a "bowtie". |
| P[3] = P[0]; // Colocate all the points on the center of the bowtie. |
| // Use the final curve section to draw the bowtie. Since the points are colocated, this |
| // curve will register as a line, which overrides innerTangents as [tan0, tan0]. That |
| // disables the first two sections of the curve because their tangents and points are |
| // all equal. |
| tan0 = prevJoinTangent; |
| prevJoinTangent = float2(0); // Disable the join section. |
| } |
| |
| if (tan1 == float2(0)) { |
| // [p0, p3, p3, p3] is a reserved pattern that means this patch is a join only. Colocate |
| // all the curve's points to ensure it gets disabled by the tessellation stages. |
| P[1] = P[2] = P[3] = P[0]; |
| // Since the points are colocated, this curve will register as a line, which overrides |
| // innerTangents as [tan0, tan0]. Setting tan1=tan0 as well results in all tangents and |
| // all points being equal, which disables every section of the curve. |
| tan1 = tan0; |
| } |
| |
| // Calculate the number of segments to chop the join into. |
| float cosTheta = cosine_between_vectors(prevJoinTangent, tan0); |
| float joinRotation = (cosTheta == 1) ? 0 : acos(cosTheta); |
| if (cross(prevJoinTangent, tan0) < 0) { |
| joinRotation = -joinRotation; |
| } |
| float joinRadialSegments = abs(joinRotation) * NUM_RADIAL_SEGMENTS_PER_RADIAN; |
| float numSegmentsInJoin = (joinRadialSegments != 0 /*Is the join non-empty?*/ && |
| JOIN_TYPE >= 0 /*Is the join not a round type?*/) |
| ? sign(JOIN_TYPE) + 1 // Non-empty bevel joins have 1 segment and miters have 2. |
| : ceil(joinRadialSegments); // Otherwise round up the number of radial segments. |
| |
| // Extends the middle join edge to the miter point. |
| float innerJoinRadiusMultiplier = 1; |
| if (JOIN_TYPE > 0 /*Is the join a miter type?*/) { |
| innerJoinRadiusMultiplier = miter_extent(cosTheta, JOIN_TYPE/*miterLimit*/); |
| } |
| |
| // Clamps join geometry to the exterior side of the junction. |
| float2 joinOutsetClamp = float2(-1, 1); |
| if (joinRadialSegments > .1 /*Does the join rotate more than 1/10 of a segment?*/) { |
| // Only clamp if the join angle is large enough to guarantee there won't be cracks on |
| // the interior side of the junction. |
| joinOutsetClamp = (joinRotation > 0) ? float2(-1, 0) : float2(0, 1); |
| } |
| |
| // Pack join args for the tessellation control stage. |
| vsJoinArgs0 = float4(numSegmentsInJoin, innerJoinRadiusMultiplier, prevJoinTangent); |
| vsJoinArgs1 = float4(atan2(prevJoinTangent), joinRotation / numSegmentsInJoin, |
| joinOutsetClamp); |
| |
| // Now find where to chop the curve so the resulting sub-curves are convex and do not rotate |
| // more than 180 degrees. We don't need to worry about cusps because the caller chops those |
| // out on the CPU. Start by finding the cubic's power basis coefficients. These define the |
| // bezier curve as: |
| // |
| // |T^3| |
| // Cubic(T) = x,y = |A 3B 3C| * |T^2| + P0 |
| // |. . .| |T | |
| // |
| // And the tangent direction (scaled by a uniform 1/3) will be: |
| // |
| // |T^2| |
| // Tangent_Direction(T) = dx,dy = |A 2B C| * |T | |
| // |. . .| |1 | |
| // |
| float2 C = P[1] - P[0]; |
| float2 D = P[2] - P[1]; |
| float2 E = P[3] - P[0]; |
| float2 B = D - C; |
| float2 A = fma(float2(-3), D, E); |
| |
| // Now find the cubic's inflection function. There are inflections where F' x F'' == 0. |
| // We formulate this as a quadratic equation: F' x F'' == aT^2 + bT + c == 0. |
| // See: https://www.microsoft.com/en-us/research/wp-content/uploads/2005/01/p1000-loop.pdf |
| // NOTE: We only need the roots, so a uniform scale factor does not affect the solution. |
| float a = cross(A, B); |
| float b = cross(A, C); |
| float c = cross(B, C); |
| float b_over_2 = b*.5; |
| float discr_over_4 = b_over_2*b_over_2 - a*c; |
| |
| float2x2 innerTangents = float2x2(0); |
| if (discr_over_4 <= 0) { |
| // The curve does not inflect. This means it might rotate more than 180 degrees instead. |
| // Craft a quadratic whose roots are the points were rotation == 180 deg and 0. (These |
| // are the points where the tangent is parallel to tan0.) |
| // |
| // Tangent_Direction(T) x tan0 == 0 |
| // (AT^2 x tan0) + (2BT x tan0) + (C x tan0) == 0 |
| // (A x C)T^2 + (2B x C)T + (C x C) == 0 [[because tan0 == P1 - P0 == C]] |
| // bT^2 + 2cT + 0 == 0 [[because A x C == b, B x C == c]] |
| // |
| // NOTE: When P0 == P1 then C != tan0, C == 0 and these roots will be undefined. But |
| // that's ok because when P0 == P1 the curve cannot rotate more than 180 degrees anyway. |
| a = b; |
| b_over_2 = c; |
| c = 0; |
| discr_over_4 = b_over_2*b_over_2; |
| innerTangents[0] = -C; |
| } |
| |
| // Solve our quadratic equation for the chop points. This is inspired by the quadratic |
| // formula from Numerical Recipes in C. |
| float q = sqrt(discr_over_4); |
| if (b_over_2 > 0) { |
| q = -q; |
| } |
| q -= b_over_2; |
| float2 chopT = float2((a != 0) ? q/a : 0, |
| (q != 0) ? c/q : 0); |
| |
| // Reposition any chop points that fall outside ~0..1 and clear their innerTangent. |
| int numOutside = 0; |
| if (chopT[0] <= kParametricEpsilon || chopT[0] >= 1 - kParametricEpsilon) { |
| innerTangents[0] = float2(0); |
| ++numOutside; |
| } |
| if (chopT[1] <= kParametricEpsilon || chopT[1] >= 1 - kParametricEpsilon) { |
| // Swap places with chopT[0]. This ensures chopT[0] is outside when numOutside > 0. |
| chopT = chopT.ts; |
| innerTangents = float2x2(0,0, innerTangents[0]); |
| ++numOutside; |
| } |
| if (numOutside == 2) { |
| chopT[1] = 2/3.0; |
| } |
| if (numOutside >= 1) { |
| chopT[0] = (chopT[1] <= .5) ? chopT[1] * .5 : fma(chopT[1], .5, .5); |
| } |
| |
| // Sort the chop points. |
| if (chopT[0] > chopT[1]) { |
| chopT = chopT.ts; |
| innerTangents = float2x2(innerTangents[1], innerTangents[0]); |
| } |
| |
| // If the curve is a straight line, point, or conic, don't chop it into sections after all. |
| if ((P[0] == P[1] && P[2] == P[3]) || isinf(P[3].y)) { |
| chopT = float2(0); |
| innerTangents = float2x2(tan0, tan0); |
| } |
| |
| // Chop the curve at chopT[0] and chopT[1]. |
| float4 ab = unchecked_mix(P[0].xyxy, P[1].xyxy, chopT.sstt); |
| float4 bc = unchecked_mix(P[1].xyxy, P[2].xyxy, chopT.sstt); |
| float4 cd = isinf(P[3].y) ? P[2].xyxy : unchecked_mix(P[2].xyxy, P[3].xyxy, chopT.sstt); |
| float4 abc = unchecked_mix(ab, bc, chopT.sstt); |
| float4 bcd = unchecked_mix(bc, cd, chopT.sstt); |
| float4 abcd = unchecked_mix(abc, bcd, chopT.sstt); |
| float4 middle = unchecked_mix(abc, bcd, chopT.ttss); |
| |
| // Find tangents at the chop points if an inner tangent wasn't specified. |
| if (innerTangents[0] == float2(0)) { |
| innerTangents[0] = bcd.xy - abc.xy; |
| } |
| if (innerTangents[1] == float2(0)) { |
| innerTangents[1] = bcd.zw - abc.zw; |
| } |
| |
| // Pack curve args for the tessellation control stage. |
| vsPts01 = float4(P[0], ab.xy); |
| vsPts23 = float4(abc.xy, abcd.xy); |
| vsPts45 = middle; |
| vsPts67 = float4(abcd.zw, bcd.zw); |
| vsPts89 = float4(cd.zw, P[3]); |
| vsTans01 = float4(tan0, innerTangents[0]); |
| vsTans23 = float4(innerTangents[1], tan1);)"); |
| if (shader.hasDynamicStroke()) { |
| v->codeAppend(R"( |
| vsStrokeArgs = float2(NUM_RADIAL_SEGMENTS_PER_RADIAN, STROKE_RADIUS);)"); |
| } |
| if (shader.hasDynamicColor()) { |
| v->codeAppend(R"( |
| vsColor = dynamicColorAttr;)"); |
| } |
| |
| if (!shader.hasDynamicColor()) { |
| // The fragment shader just outputs a uniform color. |
| const char* colorUniformName; |
| fColorUniform = uniHandler->addUniform(nullptr, kFragment_GrShaderFlag, kHalf4_GrSLType, |
| "color", &colorUniformName); |
| args.fFragBuilder->codeAppendf("half4 %s = %s;", args.fOutputColor, colorUniformName); |
| } else { |
| // Color gets passed in from the tess evaluation shader. |
| SkString flatness(args.fShaderCaps->preferFlatInterpolation() ? "flat" : ""); |
| args.fFragBuilder->declareGlobal(GrShaderVar(SkString("tesColor"), kHalf4_GrSLType, |
| TypeModifier::In, 0, SkString(), |
| flatness)); |
| args.fFragBuilder->codeAppendf("half4 %s = tesColor;", args.fOutputColor); |
| } |
| args.fFragBuilder->codeAppendf("const half4 %s = half4(1);", args.fOutputCoverage); |
| } |
| |
| void setData(const GrGLSLProgramDataManager& pdman, |
| const GrGeometryProcessor& geomProc) override { |
| const auto& shader = geomProc.cast<GrStrokeTessellateShader>(); |
| const auto& stroke = shader.fStroke; |
| |
| if (!shader.hasDynamicStroke()) { |
| GrStrokeTolerances tolerances; |
| if (!stroke.isHairlineStyle()) { |
| tolerances = GrStrokeTolerances::MakeNonHairline(shader.viewMatrix().getMaxScale(), |
| stroke.getWidth()); |
| } else { |
| // In the hairline case we transform prior to tessellation. Set up tolerances for an |
| // identity viewMatrix and a strokeWidth of 1. |
| tolerances = GrStrokeTolerances::MakeNonHairline(1, 1); |
| } |
| float strokeRadius = (stroke.isHairlineStyle()) ? .5f : stroke.getWidth() * .5; |
| pdman.set4f(fTessArgsUniform, |
| tolerances.fParametricIntolerance, // PARAMETRIC_INTOLERANCE |
| tolerances.fNumRadialSegmentsPerRadian, // NUM_RADIAL_SEGMENTS_PER_RADIAN |
| GetJoinType(shader.fStroke), // JOIN_TYPE |
| strokeRadius); // STROKE_RADIUS |
| } else { |
| SkASSERT(!stroke.isHairlineStyle()); |
| float maxScale = shader.viewMatrix().getMaxScale(); |
| pdman.set1f(fTessArgsUniform, GrStrokeTolerances::CalcParametricIntolerance(maxScale)); |
| } |
| |
| // Set up the view matrix, if any. |
| const SkMatrix& m = shader.viewMatrix(); |
| if (!m.isIdentity()) { |
| pdman.set2f(fTranslateUniform, m.getTranslateX(), m.getTranslateY()); |
| pdman.set4f(fAffineMatrixUniform, m.getScaleX(), m.getSkewY(), m.getSkewX(), |
| m.getScaleY()); |
| } |
| |
| if (!shader.hasDynamicColor()) { |
| pdman.set4fv(fColorUniform, 1, shader.fColor.vec()); |
| } |
| } |
| |
| GrGLSLUniformHandler::UniformHandle fTessArgsUniform; |
| GrGLSLUniformHandler::UniformHandle fTranslateUniform; |
| GrGLSLUniformHandler::UniformHandle fAffineMatrixUniform; |
| GrGLSLUniformHandler::UniformHandle fColorUniform; |
| }; |
| |
| SkString GrStrokeTessellateShader::getTessControlShaderGLSL( |
| const GrGLSLGeometryProcessor* glslGeomProc, |
| const char* versionAndExtensionDecls, |
| const GrGLSLUniformHandler& uniformHandler, |
| const GrShaderCaps& shaderCaps) const { |
| SkASSERT(fMode == Mode::kTessellation); |
| auto impl = static_cast<const GrStrokeTessellateShader::TessellationImpl*>(glslGeomProc); |
| |
| SkString code(versionAndExtensionDecls); |
| // Run 3 invocations: 1 for each section that the vertex shader chopped the curve into. |
| code.append("layout(vertices = 3) out;\n"); |
| code.appendf("precision highp float;\n"); |
| |
| code.appendf("#define float2 vec2\n"); |
| code.appendf("#define float3 vec3\n"); |
| code.appendf("#define float4 vec4\n"); |
| code.appendf("#define float2x2 mat2\n"); |
| code.appendf("#define float4x2 mat4x2\n"); |
| code.appendf("#define PI 3.141592653589793238\n"); |
| code.appendf("#define MAX_TESSELLATION_SEGMENTS %i.0\n", shaderCaps.maxTessellationSegments()); |
| code.appendf("#define cross cross2d\n"); // GLSL already has a function named "cross". |
| |
| const char* tessArgsName = impl->getTessArgsUniformName(uniformHandler); |
| if (!this->hasDynamicStroke()) { |
| code.appendf("uniform vec4 %s;\n", tessArgsName); |
| code.appendf("#define PARAMETRIC_INTOLERANCE %s.x\n", tessArgsName); |
| code.appendf("#define NUM_RADIAL_SEGMENTS_PER_RADIAN %s.y\n", tessArgsName); |
| } else { |
| code.appendf("uniform float %s;\n", tessArgsName); |
| code.appendf("#define PARAMETRIC_INTOLERANCE %s\n", tessArgsName); |
| code.appendf("#define NUM_RADIAL_SEGMENTS_PER_RADIAN vsStrokeArgs[0].x\n"); |
| } |
| |
| code.append(kLengthPow2Fn); |
| append_wangs_formula_fn(&code, this->hasConics()); |
| code.append(kAtan2Fn); |
| code.append(kCosineBetweenVectorsFn); |
| code.append(kMiterExtentFn); |
| code.append(R"( |
| float cross2d(vec2 a, vec2 b) { |
| return determinant(mat2(a,b)); |
| })"); |
| |
| code.append(R"( |
| in vec4 vsJoinArgs0[]; |
| in vec4 vsJoinArgs1[]; |
| in vec4 vsPts01[]; |
| in vec4 vsPts23[]; |
| in vec4 vsPts45[]; |
| in vec4 vsPts67[]; |
| in vec4 vsPts89[]; |
| in vec4 vsTans01[]; |
| in vec4 vsTans23[];)"); |
| if (this->hasDynamicStroke()) { |
| code.append(R"( |
| in vec2 vsStrokeArgs[];)"); |
| } |
| if (this->hasDynamicColor()) { |
| code.append(R"( |
| in mediump vec4 vsColor[];)"); |
| } |
| |
| code.append(R"( |
| out vec4 tcsPts01[]; |
| out vec4 tcsPt2Tan0[]; |
| out vec4 tcsTessArgs[]; // [numCombinedSegments, numParametricSegments, angle0, radsPerSegment] |
| patch out vec4 tcsJoinArgs0; // [numSegmentsInJoin, innerJoinRadiusMultiplier, |
| // prevJoinTangent.xy] |
| patch out vec4 tcsJoinArgs1; // [joinAngle0, radsPerJoinSegment, joinOutsetClamp.xy] |
| patch out vec4 tcsEndPtEndTan;)"); |
| if (this->hasDynamicStroke()) { |
| code.append(R"( |
| patch out float tcsStrokeRadius;)"); |
| } |
| if (this->hasDynamicColor()) { |
| code.append(R"( |
| patch out mediump vec4 tcsColor;)"); |
| } |
| |
| code.append(R"( |
| void main() { |
| // Forward join args to the evaluation stage. |
| tcsJoinArgs0 = vsJoinArgs0[0]; |
| tcsJoinArgs1 = vsJoinArgs1[0];)"); |
| if (this->hasDynamicStroke()) { |
| code.append(R"( |
| tcsStrokeRadius = vsStrokeArgs[0].y;)"); |
| } |
| if (this->hasDynamicColor()) { |
| code.append(R"( |
| tcsColor = vsColor[0];)"); |
| } |
| |
| code.append(R"( |
| // Unpack the curve args from the vertex shader. |
| mat4x2 P; |
| mat2 tangents; |
| if (gl_InvocationID == 0) { |
| // This is the first section of the curve. |
| P = mat4x2(vsPts01[0], vsPts23[0]); |
| tangents = mat2(vsTans01[0]); |
| } else if (gl_InvocationID == 1) { |
| // This is the middle section of the curve. |
| P = mat4x2(vsPts23[0].zw, vsPts45[0], vsPts67[0].xy); |
| tangents = mat2(vsTans01[0].zw, vsTans23[0].xy); |
| } else { |
| // This is the final section of the curve. |
| P = mat4x2(vsPts67[0], vsPts89[0]); |
| tangents = mat2(vsTans23[0]); |
| } |
| |
| // Calculate the number of parametric segments. The final tessellated strip will be a |
| // composition of these parametric segments as well as radial segments. |
| float w = isinf(P[3].y) ? P[3].x : -1.0; // w<0 means the curve is an integral cubic. |
| float numParametricSegments = wangs_formula(P, w, PARAMETRIC_INTOLERANCE); |
| if (P[0] == P[1] && P[2] == P[3]) { |
| // This is how the patch builder articulates lineTos but Wang's formula returns |
| // >>1 segment in this scenario. Assign 1 parametric segment. |
| numParametricSegments = 1.0; |
| } |
| |
| // Determine the curve's start angle. |
| float angle0 = atan2(tangents[0]); |
| |
| // Determine the curve's total rotation. The vertex shader ensures our curve does not rotate |
| // more than 180 degrees or inflect, so the inverse cosine has enough range. |
| float cosTheta = cosine_between_vectors(tangents[0], tangents[1]); |
| float rotation = acos(cosTheta); |
| |
| // Adjust sign of rotation to match the direction the curve turns. |
| // NOTE: Since the curve is not allowed to inflect, we can just check F'(.5) x F''(.5). |
| // NOTE: F'(.5) x F''(.5) has the same sign as (P2 - P0) x (P3 - P1) |
| float turn = isinf(P[3].y) ? cross2d(P[1] - P[0], P[2] - P[1]) |
| : cross2d(P[2] - P[0], P[3] - P[1]); |
| if (turn == 0.0) { // This is the case for joins and cusps where points are co-located. |
| turn = determinant(tangents); |
| } |
| if (turn < 0.0) { |
| rotation = -rotation; |
| } |
| |
| // Calculate the number of evenly spaced radial segments to chop this section of the curve |
| // into. Radial segments divide the curve's rotation into even steps. The final tessellated |
| // strip will be a composition of both parametric and radial segments. |
| float numRadialSegments = abs(rotation) * NUM_RADIAL_SEGMENTS_PER_RADIAN; |
| numRadialSegments = max(ceil(numRadialSegments), 1.0); |
| |
| // The first and last edges are shared by both the parametric and radial sets of edges, so |
| // the total number of edges is: |
| // |
| // numCombinedEdges = numParametricEdges + numRadialEdges - 2 |
| // |
| // It's also important to differentiate between the number of edges and segments in a strip: |
| // |
| // numCombinedSegments = numCombinedEdges - 1 |
| // |
| // So the total number of segments in the combined strip is: |
| // |
| // numCombinedSegments = numParametricEdges + numRadialEdges - 2 - 1 |
| // = numParametricSegments + 1 + numRadialSegments + 1 - 2 - 1 |
| // = numParametricSegments + numRadialSegments - 1 |
| // |
| float numCombinedSegments = numParametricSegments + numRadialSegments - 1.0; |
| |
| if (P[0] == P[3] && tangents[0] == tangents[1]) { |
| // The vertex shader intentionally disabled our section. Set numCombinedSegments to 0. |
| numCombinedSegments = 0.0; |
| } |
| |
| // Pack the args for the evaluation stage. |
| tcsPts01[gl_InvocationID] = vec4(P[0], P[1]); |
| tcsPt2Tan0[gl_InvocationID] = vec4(P[2], tangents[0]); |
| tcsTessArgs[gl_InvocationID] = vec4(numCombinedSegments, numParametricSegments, angle0, |
| rotation / numRadialSegments); |
| if (gl_InvocationID == 2) { |
| tcsEndPtEndTan = vec4(P[3], tangents[1]); |
| } |
| |
| barrier(); |
| |
| // Tessellate a quad strip with enough segments for the join plus all 3 curve sections |
| // combined. |
| float numTotalCombinedSegments = tcsJoinArgs0.x + tcsTessArgs[0].x + tcsTessArgs[1].x + |
| tcsTessArgs[2].x; |
| |
| if (tcsJoinArgs0.x != 0.0 && tcsJoinArgs0.x != numTotalCombinedSegments) { |
| // We are tessellating a quad strip with both a single-sided join and a double-sided |
| // stroke. Add one more edge to the join. This new edge will fall parallel with the |
| // first edge of the stroke, eliminating artifacts on the transition from single |
| // sided to double. |
| ++tcsJoinArgs0.x; |
| ++numTotalCombinedSegments; |
| } |
| |
| numTotalCombinedSegments = min(numTotalCombinedSegments, MAX_TESSELLATION_SEGMENTS); |
| gl_TessLevelInner[0] = numTotalCombinedSegments; |
| gl_TessLevelInner[1] = 2.0; |
| gl_TessLevelOuter[0] = 2.0; |
| gl_TessLevelOuter[1] = numTotalCombinedSegments; |
| gl_TessLevelOuter[2] = 2.0; |
| gl_TessLevelOuter[3] = numTotalCombinedSegments; |
| })"); |
| |
| return code; |
| } |
| |
| // Computes the location and tangent direction of the stroke edge with the integral id |
| // "combinedEdgeID", where combinedEdgeID is the sorted-order index of parametric and radial edges. |
| static void append_eval_stroke_edge_fn(SkString* code, bool hasConics) { |
| code->append(R"( |
| void eval_stroke_edge(in float4x2 P, in float w, in float numParametricSegments, |
| in float combinedEdgeID, in float2 tan0, in float radsPerSegment, |
| in float angle0, out float2 tangent, out float2 position) { |
| // Start by finding the tangent function's power basis coefficients. These define a tangent |
| // direction (scaled by some uniform value) as: |
| // |T^2| |
| // Tangent_Direction(T) = dx,dy = |A 2B C| * |T | |
| // |. . .| |1 | |
| float2 A, B, C = P[1] - P[0]; |
| float2 D = P[3] - P[0];)"); |
| if (hasConics) { |
| code->append(R"( |
| if (w >= 0.0) { |
| // P0..P2 represent a conic and P3==P2. The derivative of a conic has a cumbersome |
| // order-4 denominator. However, this isn't necessary if we are only interested in a |
| // vector in the same *direction* as a given tangent line. Since the denominator scales |
| // dx and dy uniformly, we can throw it out completely after evaluating the derivative |
| // with the standard quotient rule. This leaves us with a simpler quadratic function |
| // that we use to find a tangent. |
| C *= w; |
| B = .5*D - C; |
| A = (w - 1.0) * D; |
| P[1] *= w; |
| } else {)"); |
| } else { |
| code->append(R"( |
| {)"); |
| } |
| code->append(R"( |
| float2 E = P[2] - P[1]; |
| B = E - C; |
| A = fma(float2(-3), E, D); |
| } |
| |
| // Now find the coefficients that give a tangent direction from a parametric edge ID: |
| // |
| // |parametricEdgeID^2| |
| // Tangent_Direction(parametricEdgeID) = dx,dy = |A B_ C_| * |parametricEdgeID | |
| // |. . .| |1 | |
| // |
| float2 B_ = B * (numParametricSegments * 2.0); |
| float2 C_ = C * (numParametricSegments * numParametricSegments); |
| |
| // Run a binary search to determine the highest parametric edge that is located on or before |
| // the combinedEdgeID. A combined ID is determined by the sum of complete parametric and |
| // radial segments behind it. i.e., find the highest parametric edge where: |
| // |
| // parametricEdgeID + floor(numRadialSegmentsAtParametricT) <= combinedEdgeID |
| // |
| float lastParametricEdgeID = 0.0; |
| float maxParametricEdgeID = min(numParametricSegments - 1.0, combinedEdgeID); |
| float2 tan0norm = normalize(tan0); |
| float negAbsRadsPerSegment = -abs(radsPerSegment); |
| float maxRotation0 = (1.0 + combinedEdgeID) * abs(radsPerSegment); |
| for (int exp = MAX_PARAMETRIC_SEGMENTS_LOG2 - 1; exp >= 0; --exp) { |
| // Test the parametric edge at lastParametricEdgeID + 2^exp. |
| float testParametricID = lastParametricEdgeID + float(1 << exp); |
| if (testParametricID <= maxParametricEdgeID) { |
| float2 testTan = fma(float2(testParametricID), A, B_); |
| testTan = fma(float2(testParametricID), testTan, C_); |
| float cosRotation = dot(normalize(testTan), tan0norm); |
| float maxRotation = fma(testParametricID, negAbsRadsPerSegment, maxRotation0); |
| maxRotation = min(maxRotation, PI); |
| // Is rotation <= maxRotation? (i.e., is the number of complete radial segments |
| // behind testT, + testParametricID <= combinedEdgeID?) |
| if (cosRotation >= cos(maxRotation)) { |
| // testParametricID is on or before the combinedEdgeID. Keep it! |
| lastParametricEdgeID = testParametricID; |
| } |
| } |
| } |
| |
| // Find the T value of the parametric edge at lastParametricEdgeID. |
| float parametricT = lastParametricEdgeID / numParametricSegments; |
| |
| // Now that we've identified the highest parametric edge on or before the combinedEdgeID, |
| // the highest radial edge is easy: |
| float lastRadialEdgeID = combinedEdgeID - lastParametricEdgeID; |
| |
| // Find the tangent vector on the edge at lastRadialEdgeID. |
| float radialAngle = fma(lastRadialEdgeID, radsPerSegment, angle0); |
| tangent = float2(cos(radialAngle), sin(radialAngle)); |
| float2 norm = float2(-tangent.y, tangent.x); |
| |
| // Find the T value where the cubic's tangent is orthogonal to norm. This is a quadratic: |
| // |
| // dot(norm, Tangent_Direction(T)) == 0 |
| // |
| // |T^2| |
| // norm * |A 2B C| * |T | == 0 |
| // |. . .| |1 | |
| // |
| float3 coeffs = norm * float3x2(A,B,C); |
| float a=coeffs.x, b_over_2=coeffs.y, c=coeffs.z; |
| float discr_over_4 = max(b_over_2*b_over_2 - a*c, 0.0); |
| float q = sqrt(discr_over_4); |
| if (b_over_2 > 0.0) { |
| q = -q; |
| } |
| q -= b_over_2; |
| |
| // Roots are q/a and c/q. Since each curve section does not inflect or rotate more than 180 |
| // degrees, there can only be one tangent orthogonal to "norm" inside 0..1. Pick the root |
| // nearest .5. |
| float _5qa = -.5*q*a; |
| float2 root = (abs(fma(q,q,_5qa)) < abs(fma(a,c,_5qa))) ? float2(q,a) : float2(c,q); |
| float radialT = (root.t != 0.0) ? root.s / root.t : 0.0; |
| radialT = clamp(radialT, 0.0, 1.0); |
| |
| if (lastRadialEdgeID == 0.0) { |
| // The root finder above can become unstable when lastRadialEdgeID == 0 (e.g., if there |
| // are roots at exatly 0 and 1 both). radialT should always == 0 in this case. |
| radialT = 0.0; |
| } |
| |
| // Now that we've identified the T values of the last parametric and radial edges, our final |
| // T value for combinedEdgeID is whichever is larger. |
| float T = max(parametricT, radialT); |
| |
| // Evaluate the cubic at T. Use De Casteljau's for its accuracy and stability. |
| float2 ab = unchecked_mix(P[0], P[1], T); |
| float2 bc = unchecked_mix(P[1], P[2], T); |
| float2 cd = unchecked_mix(P[2], P[3], T); |
| float2 abc = unchecked_mix(ab, bc, T); |
| float2 bcd = unchecked_mix(bc, cd, T); |
| float2 abcd = unchecked_mix(abc, bcd, T);)"); |
| |
| if (hasConics) { |
| code->append(R"( |
| // Evaluate the conic weights at T. |
| float u = unchecked_mix(1.0, w, T); |
| float v = unchecked_mix(w, 1.0, T); |
| float uv = unchecked_mix(u, v, T);)"); |
| } |
| |
| code->appendf(R"( |
| position =%s abcd;)", (hasConics) ? " (w >= 0.0) ? abc/uv :" : ""); |
| |
| code->appendf(R"( |
| // If we went with T=parametricT, then update the tangent. Otherwise leave it at the radial |
| // tangent found previously. (In the event that parametricT == radialT, we keep the radial |
| // tangent.) |
| if (T != radialT) {)"); |
| code->appendf(R"( |
| tangent =%s bcd - abc;)", (hasConics) ? " (w >= 0.0) ? bc*u - ab*v :" : ""); |
| code->appendf(R"( |
| } |
| })"); |
| } |
| |
| SkString GrStrokeTessellateShader::getTessEvaluationShaderGLSL( |
| const GrGLSLGeometryProcessor* glslGeomProc, |
| const char* versionAndExtensionDecls, |
| const GrGLSLUniformHandler& uniformHandler, |
| const GrShaderCaps& shaderCaps) const { |
| SkASSERT(fMode == Mode::kTessellation); |
| auto impl = static_cast<const GrStrokeTessellateShader::TessellationImpl*>(glslGeomProc); |
| |
| SkString code(versionAndExtensionDecls); |
| code.append("layout(quads, equal_spacing, ccw) in;\n"); |
| code.appendf("precision highp float;\n"); |
| |
| code.appendf("#define float2 vec2\n"); |
| code.appendf("#define float3 vec3\n"); |
| code.appendf("#define float4 vec4\n"); |
| code.appendf("#define float2x2 mat2\n"); |
| code.appendf("#define float3x2 mat3x2\n"); |
| code.appendf("#define float4x2 mat4x2\n"); |
| code.appendf("#define PI 3.141592653589793238\n"); |
| code.appendf("#define MAX_PARAMETRIC_SEGMENTS_LOG2 %i\n", |
| SkNextLog2(shaderCaps.maxTessellationSegments())); |
| |
| if (!this->hasDynamicStroke()) { |
| const char* tessArgsName = impl->getTessArgsUniformName(uniformHandler); |
| code.appendf("uniform vec4 %s;\n", tessArgsName); |
| code.appendf("#define STROKE_RADIUS %s.w\n", tessArgsName); |
| } else { |
| code.appendf("#define STROKE_RADIUS tcsStrokeRadius\n"); |
| } |
| |
| if (!this->viewMatrix().isIdentity()) { |
| const char* translateName = impl->getTranslateUniformName(uniformHandler); |
| code.appendf("uniform vec2 %s;\n", translateName); |
| code.appendf("#define TRANSLATE %s\n", translateName); |
| if (!fStroke.isHairlineStyle()) { |
| // In the normal case we need the affine matrix too. (In the hairline case we already |
| // applied the affine matrix in the vertex shader.) |
| const char* affineMatrixName = impl->getAffineMatrixUniformName(uniformHandler); |
| code.appendf("uniform vec4 %s;\n", affineMatrixName); |
| code.appendf("#define AFFINE_MATRIX mat2(%s)\n", affineMatrixName); |
| } |
| } |
| |
| code.append(R"( |
| in vec4 tcsPts01[]; |
| in vec4 tcsPt2Tan0[]; |
| in vec4 tcsTessArgs[]; // [numCombinedSegments, numParametricSegments, angle0, radsPerSegment] |
| patch in vec4 tcsJoinArgs0; // [numSegmentsInJoin, innerJoinRadiusMultiplier, |
| // prevJoinTangent.xy] |
| patch in vec4 tcsJoinArgs1; // [joinAngle0, radsPerJoinSegment, joinOutsetClamp.xy] |
| patch in vec4 tcsEndPtEndTan;)"); |
| if (this->hasDynamicStroke()) { |
| code.append(R"( |
| patch in float tcsStrokeRadius;)"); |
| } |
| if (this->hasDynamicColor()) { |
| code.appendf(R"( |
| patch in mediump vec4 tcsColor; |
| %s out mediump vec4 tesColor;)", shaderCaps.preferFlatInterpolation() ? "flat" : ""); |
| } |
| |
| code.append(R"( |
| uniform vec4 sk_RTAdjust;)"); |
| |
| code.append(kUncheckedMixFn); |
| append_eval_stroke_edge_fn(&code, this->hasConics()); |
| |
| code.append(R"( |
| void main() { |
| // Our patch is composed of exactly "numTotalCombinedSegments + 1" stroke-width edges that |
| // run orthogonal to the curve and make a strip of "numTotalCombinedSegments" quads. |
| // Determine which discrete edge belongs to this invocation. An edge can either come from a |
| // parametric segment or a radial one. |
| float numSegmentsInJoin = tcsJoinArgs0.x; |
| float numTotalCombinedSegments = numSegmentsInJoin + tcsTessArgs[0].x + tcsTessArgs[1].x + |
| tcsTessArgs[2].x; |
| float totalEdgeID = round(gl_TessCoord.x * numTotalCombinedSegments); |
| |
| // Furthermore, the vertex shader may have chopped the curve into 3 different sections. |
| // Determine which section we belong to, and where we fall relative to its first edge. |
| float localEdgeID = totalEdgeID; |
| mat4x2 P; |
| vec2 tan0; |
| vec3 tessellationArgs; |
| float strokeRadius = STROKE_RADIUS; |
| vec2 strokeOutsetClamp = vec2(-1, 1); |
| if (localEdgeID < numSegmentsInJoin || numSegmentsInJoin == numTotalCombinedSegments) { |
| // Our edge belongs to the join preceding the curve. |
| P = mat4x2(tcsPts01[0].xyxy, tcsPts01[0].xyxy); |
| tan0 = tcsJoinArgs0.zw; |
| tessellationArgs = vec3(1, tcsJoinArgs1.xy); |
| strokeRadius *= (localEdgeID == 1.0) ? tcsJoinArgs0.y : 1.0; |
| strokeOutsetClamp = tcsJoinArgs1.zw; |
| } else if ((localEdgeID -= numSegmentsInJoin) < tcsTessArgs[0].x) { |
| // Our edge belongs to the first curve section. |
| P = mat4x2(tcsPts01[0], tcsPt2Tan0[0].xy, tcsPts01[1].xy); |
| tan0 = tcsPt2Tan0[0].zw; |
| tessellationArgs = tcsTessArgs[0].yzw; |
| } else if ((localEdgeID -= tcsTessArgs[0].x) < tcsTessArgs[1].x) { |
| // Our edge belongs to the second curve section. |
| P = mat4x2(tcsPts01[1], tcsPt2Tan0[1].xy, tcsPts01[2].xy); |
| tan0 = tcsPt2Tan0[1].zw; |
| tessellationArgs = tcsTessArgs[1].yzw; |
| } else { |
| // Our edge belongs to the third curve section. |
| localEdgeID -= tcsTessArgs[1].x; |
| P = mat4x2(tcsPts01[2], tcsPt2Tan0[2].xy, tcsEndPtEndTan.xy); |
| tan0 = tcsPt2Tan0[2].zw; |
| tessellationArgs = tcsTessArgs[2].yzw; |
| } |
| float numParametricSegments = tessellationArgs.x; |
| float angle0 = tessellationArgs.y; |
| float radsPerSegment = tessellationArgs.z; |
| |
| float w = -1.0; // w<0 means the curve is an integral cubic.)"); |
| |
| if (this->hasConics()) { |
| code.append(R"( |
| if (isinf(P[3].y)) { |
| w = P[3].x; // The curve is actually a conic. |
| P[3] = P[2]; // Setting p3 equal to p2 works for the remaining rotational logic. |
| })"); |
| } |
| |
| code.append(R"( |
| float2 tangent, position; |
| eval_stroke_edge(P, w, numParametricSegments, localEdgeID, tan0, radsPerSegment, angle0, |
| tangent, position); |
| |
| if (localEdgeID == 0.0) { |
| // The first local edge of each section uses the provided tan0. This ensures continuous |
| // rotation across chops made by the vertex shader as well as crack-free seaming between |
| // patches. (NOTE: position is always equal to P[0] here when localEdgeID==0.) |
| tangent = tan0; |
| } |
| |
| if (gl_TessCoord.x == 1.0) { |
| // The final edge of the quad strip always uses the provided endPt and endTan. This |
| // ensures crack-free seaming between patches. |
| tangent = tcsEndPtEndTan.zw; |
| position = P[3]; |
| } |
| |
| // Determine how far to outset our vertex orthogonally from the curve. |
| float outset = gl_TessCoord.y * 2.0 - 1.0; |
| outset = clamp(outset, strokeOutsetClamp.x, strokeOutsetClamp.y); |
| outset *= strokeRadius; |
| |
| vec2 vertexPos = position + normalize(vec2(-tangent.y, tangent.x)) * outset;)"); |
| |
| if (!this->viewMatrix().isIdentity()) { |
| if (!fStroke.isHairlineStyle()) { |
| // Normal case. Do the transform after tessellation. |
| code.append("vertexPos = AFFINE_MATRIX * vertexPos + TRANSLATE;"); |
| } else { |
| // Hairline case. The scale and skew already happened before tessellation. |
| code.append("vertexPos = vertexPos + TRANSLATE;"); |
| } |
| } |
| |
| code.append(R"( |
| gl_Position = vec4(vertexPos * sk_RTAdjust.xz + sk_RTAdjust.yw, 0.0, 1.0);)"); |
| |
| if (this->hasDynamicColor()) { |
| code.append(R"( |
| tesColor = tcsColor;)"); |
| } |
| |
| code.append(R"( |
| })"); |
| |
| return code; |
| } |
| |
| class GrStrokeTessellateShader::IndirectImpl : public GrGLSLGeometryProcessor { |
| void onEmitCode(EmitArgs& args, GrGPArgs* gpArgs) override { |
| const auto& shader = args.fGeomProc.cast<GrStrokeTessellateShader>(); |
| SkPaint::Join joinType = shader.fStroke.getJoin(); |
| args.fVaryingHandler->emitAttributes(shader); |
| |
| // Constants. |
| args.fVertBuilder->defineConstant("MAX_PARAMETRIC_SEGMENTS_LOG2", |
| GrTessellationPathRenderer::kMaxResolveLevel); |
| args.fVertBuilder->defineConstant("float", "PI", "3.141592653589793238"); |
| |
| // Helper functions. |
| if (shader.hasDynamicStroke()) { |
| args.fVertBuilder->insertFunction(kNumRadialSegmentsPerRadian); |
| } |
| args.fVertBuilder->insertFunction(kAtan2Fn); |
| args.fVertBuilder->insertFunction(kLengthPow2Fn); |
| args.fVertBuilder->insertFunction(kMiterExtentFn); |
| args.fVertBuilder->insertFunction(kUncheckedMixFn); |
| args.fVertBuilder->insertFunction(kCosineBetweenVectorsFn); |
| append_wangs_formula_fn(&args.fVertBuilder->functions(), shader.hasConics()); |
| append_eval_stroke_edge_fn(&args.fVertBuilder->functions(), shader.hasConics()); |
| |
| // Tessellation control uniforms and/or dynamic attributes. |
| if (!shader.hasDynamicStroke()) { |
| // [PARAMETRIC_INTOLERANCE, NUM_RADIAL_SEGMENTS_PER_RADIAN, JOIN_TYPE, STROKE_RADIUS] |
| const char* tessArgsName; |
| fTessControlArgsUniform = args.fUniformHandler->addUniform( |
| nullptr, kVertex_GrShaderFlag, kFloat4_GrSLType, "tessControlArgs", |
| &tessArgsName); |
| args.fVertBuilder->codeAppendf(R"( |
| float PARAMETRIC_INTOLERANCE = %s.x; |
| float NUM_RADIAL_SEGMENTS_PER_RADIAN = %s.y; |
| float JOIN_TYPE = %s.z; |
| float STROKE_RADIUS = %s.w;)", tessArgsName, tessArgsName, tessArgsName, tessArgsName); |
| } else { |
| const char* parametricIntoleranceName; |
| fTessControlArgsUniform = args.fUniformHandler->addUniform( |
| nullptr, kVertex_GrShaderFlag, kFloat_GrSLType, "parametricIntolerance", |
| ¶metricIntoleranceName); |
| args.fVertBuilder->codeAppendf(R"( |
| float PARAMETRIC_INTOLERANCE = %s; |
| float STROKE_RADIUS = dynamicStrokeAttr.x; |
| float NUM_RADIAL_SEGMENTS_PER_RADIAN = num_radial_segments_per_radian( |
| PARAMETRIC_INTOLERANCE, STROKE_RADIUS); |
| float JOIN_TYPE = dynamicStrokeAttr.y;)", parametricIntoleranceName); |
| } |
| |
| // View matrix uniforms. |
| if (!shader.viewMatrix().isIdentity()) { |
| const char* translateName, *affineMatrixName; |
| fAffineMatrixUniform = args.fUniformHandler->addUniform( |
| nullptr, kVertex_GrShaderFlag, kFloat4_GrSLType, "affineMatrix", |
| &affineMatrixName); |
| fTranslateUniform = args.fUniformHandler->addUniform( |
| nullptr, kVertex_GrShaderFlag, kFloat2_GrSLType, "translate", &translateName); |
| args.fVertBuilder->codeAppendf("float2x2 AFFINE_MATRIX = float2x2(%s);\n", |
| affineMatrixName); |
| args.fVertBuilder->codeAppendf("float2 TRANSLATE = %s;\n", translateName); |
| } |
| |
| // Tessellation code. |
| args.fVertBuilder->codeAppend(R"( |
| float4x2 P = float4x2(pts01Attr, pts23Attr); |
| float2 lastControlPoint = argsAttr.xy; |
| float w = -1; // w<0 means the curve is an integral cubic.)"); |
| if (shader.hasConics()) { |
| args.fVertBuilder->codeAppend(R"( |
| if (isinf(P[3].y)) { |
| w = P[3].x; // The curve is actually a conic. |
| P[3] = P[2]; // Setting p3 equal to p2 works for the remaining rotational logic. |
| })"); |
| } |
| if (shader.fStroke.isHairlineStyle() && !shader.viewMatrix().isIdentity()) { |
| // Hairline case. Transform the points before tessellation. We can still hold off on the |
| // translate until the end; we just need to perform the scale and skew right now. |
| args.fVertBuilder->codeAppend(R"( |
| P = AFFINE_MATRIX * P; |
| lastControlPoint = AFFINE_MATRIX * lastControlPoint;)"); |
| } |
| args.fVertBuilder->codeAppend(R"( |
| float numTotalEdges = abs(argsAttr.z); |
| |
| // Find how many parametric segments this stroke requires. |
| float numParametricSegments = min(wangs_formula(P, w, PARAMETRIC_INTOLERANCE), |
| float(1 << MAX_PARAMETRIC_SEGMENTS_LOG2)); |
| if (P[0] == P[1] && P[2] == P[3]) { |
| // This is how we describe lines, but Wang's formula does not return 1 in this case. |
| numParametricSegments = 1; |
| } |
| |
| // Find the starting and ending tangents. |
| float2 tan0 = ((P[0] == P[1]) ? (P[1] == P[2]) ? P[3] : P[2] : P[1]) - P[0]; |
| float2 tan1 = P[3] - ((P[3] == P[2]) ? (P[2] == P[1]) ? P[0] : P[1] : P[2]); |
| if (tan0 == float2(0)) { |
| // The stroke is a point. This special case tells us to draw a stroke-width circle as a |
| // 180 degree point stroke instead. |
| tan0 = float2(1,0); |
| tan1 = float2(-1,0); |
| })"); |
| |
| if (shader.fStroke.getJoin() == SkPaint::kRound_Join || shader.hasDynamicStroke()) { |
| args.fVertBuilder->codeAppend(R"( |
| // Determine how many edges to give to the round join. We emit the first and final edges |
| // of the join twice: once full width and once restricted to half width. This guarantees |
| // perfect seaming by matching the vertices from the join as well as from the strokes on |
| // either side. |
| float joinRads = acos(cosine_between_vectors(P[0] - lastControlPoint, tan0)); |
| float numRadialSegmentsInJoin = max(ceil(joinRads * NUM_RADIAL_SEGMENTS_PER_RADIAN), 1); |
| // +2 because we emit the beginning and ending edges twice (see above comment). |
| float numEdgesInJoin = numRadialSegmentsInJoin + 2; |
| // The stroke section needs at least two edges. Don't assign more to the join than |
| // "numTotalEdges - 2". |
| numEdgesInJoin = min(numEdgesInJoin, numTotalEdges - 2); |
| // Negative argsAttr.z means the join is a chop, and chop joins get exactly one segment. |
| if (argsAttr.z < 0) { |
| // +2 because we emit the beginning and ending edges twice (see above comment). |
| numEdgesInJoin = 1 + 2; |
| })"); |
| if (shader.hasDynamicStroke()) { |
| args.fVertBuilder->codeAppend(R"( |
| if (JOIN_TYPE >= 0 /*Is the join not a round type?*/) { |
| // Bevel and miter joins get 1 and 2 segments respectively. |
| // +2 because we emit the beginning and ending edges twice (see above comments). |
| numEdgesInJoin = sign(JOIN_TYPE) + 1 + 2; |
| })"); |
| } |
| } else { |
| args.fVertBuilder->codeAppendf(R"( |
| float numEdgesInJoin = %i;)", NumExtraEdgesInIndirectJoin(joinType)); |
| } |
| |
| args.fVertBuilder->codeAppend(R"( |
| // Find which direction the curve turns. |
| // NOTE: Since the curve is not allowed to inflect, we can just check F'(.5) x F''(.5). |
| // NOTE: F'(.5) x F''(.5) has the same sign as (P2 - P0) x (P3 - P1) |
| float turn = cross(P[2] - P[0], P[3] - P[1]); |
| float combinedEdgeID = float(sk_VertexID >> 1) - numEdgesInJoin; |
| if (combinedEdgeID < 0) { |
| tan1 = tan0; |
| // Don't let tan0 become zero. The code as-is isn't built to handle that case. tan0=0 |
| // means the join is disabled, and to disable it with the existing code we can leave |
| // tan0 equal to tan1. |
| if (lastControlPoint != P[0]) { |
| tan0 = P[0] - lastControlPoint; |
| } |
| turn = cross(tan0, tan1); |
| } |
| |
| // Calculate the curve's starting angle and rotation. |
| float angle0 = atan2(tan0); |
| float cosTheta = cosine_between_vectors(tan0, tan1); |
| float rotation = acos(cosTheta); |
| if (turn < 0) { |
| // Adjust sign of rotation to match the direction the curve turns. |
| rotation = -rotation; |
| } |
| |
| float numRadialSegments; |
| float outset = ((sk_VertexID & 1) == 0) ? +1 : -1; |
| if (combinedEdgeID < 0) { |
| // We belong to the preceding join. The first and final edges get duplicated, so we only |
| // have "numEdgesInJoin - 2" segments. |
| numRadialSegments = numEdgesInJoin - 2; |
| numParametricSegments = 1; // Joins don't have parametric segments. |
| P = float4x2(P[0], P[0], P[0], P[0]); // Colocate all points on the junction point. |
| // Shift combinedEdgeID to the range [-1, numRadialSegments]. This duplicates the first |
| // edge and lands one edge at the very end of the join. (The duplicated final edge will |
| // actually come from the section of our strip that belongs to the stroke.) |
| combinedEdgeID += numRadialSegments + 1; |
| // We normally restrict the join on one side of the junction, but if the tangents are |
| // nearly equivalent this could theoretically result in bad seaming and/or cracks on the |
| // side we don't put it on. If the tangents are nearly equivalent then we leave the join |
| // double-sided. |
| float sinEpsilon = 1e-2; // ~= sin(180deg / 3000) |
| bool tangentsNearlyParallel = |
| (abs(turn) * inversesqrt(dot(tan0, tan0) * dot(tan1, tan1))) < sinEpsilon; |
| if (!tangentsNearlyParallel || dot(tan0, tan1) < 0) { |
| // There are two edges colocated at the beginning. Leave the first one double sided |
| // for seaming with the previous stroke. (The double sided edge at the end will |
| // actually come from the section of our strip that belongs to the stroke.) |
| if (combinedEdgeID >= 0) { |
| outset = (turn < 0) ? min(outset, 0) : max(outset, 0); |
| } |
| } |
| combinedEdgeID = max(combinedEdgeID, 0); |
| } else { |
| // We belong to the stroke. |
| float maxCombinedSegments = numTotalEdges - numEdgesInJoin - 1; |
| numRadialSegments = max(ceil(abs(rotation) * NUM_RADIAL_SEGMENTS_PER_RADIAN), 1); |
| numRadialSegments = min(numRadialSegments, maxCombinedSegments); |
| numParametricSegments = min(numParametricSegments, |
| maxCombinedSegments - numRadialSegments + 1); |
| } |
| |
| float numCombinedSegments = numParametricSegments + numRadialSegments - 1; |
| float radsPerSegment = rotation / numRadialSegments;)"); |
| |
| if (joinType == SkPaint::kMiter_Join || shader.hasDynamicStroke()) { |
| args.fVertBuilder->codeAppendf(R"( |
| // Vertices #4 and #5 belong to the edge of the join that extends to the miter point. |
| if ((sk_VertexID | 1) == (4 | 5) && %s) { |
| outset *= miter_extent(cosTheta, JOIN_TYPE/*miterLimit*/); |
| })", shader.hasDynamicStroke() ? "JOIN_TYPE > 0/*Is the join a miter type?*/" : "true"); |
| } |
| |
| args.fVertBuilder->codeAppend(R"( |
| float2 strokeCoord, tangent; |
| if (0 < combinedEdgeID && combinedEdgeID < numCombinedSegments) { |
| eval_stroke_edge(P, w, numParametricSegments, combinedEdgeID, tan0, radsPerSegment, |
| angle0, tangent, strokeCoord); |
| } else { |
| // Edges at the beginning and end of the strip use exact endpoints and tangents. This |
| // ensures crack-free seaming between instances. |
| strokeCoord = (combinedEdgeID == 0) ? P[0] : P[3]; |
| tangent = (combinedEdgeID == 0) ? tan0 : tan1; |
| if (combinedEdgeID > numCombinedSegments) { |
| outset = 0; // The strip has more edges than we need. Drop this one. |
| } |
| } |
| |
| float2 ortho = normalize(float2(tangent.y, -tangent.x)); |
| strokeCoord += ortho * (STROKE_RADIUS * outset);)"); |
| |
| if (shader.viewMatrix().isIdentity()) { |
| // No transform matrix. |
| gpArgs->fPositionVar.set(kFloat2_GrSLType, "strokeCoord"); |
| gpArgs->fLocalCoordVar.set(kFloat2_GrSLType, "strokeCoord"); |
| } else if (!shader.fStroke.isHairlineStyle()) { |
| // Normal case. Do the transform after tessellation. |
| args.fVertBuilder->codeAppend(R"( |
| float2 devCoord = AFFINE_MATRIX * strokeCoord + TRANSLATE;)"); |
| gpArgs->fPositionVar.set(kFloat2_GrSLType, "devCoord"); |
| gpArgs->fLocalCoordVar.set(kFloat2_GrSLType, "strokeCoord"); |
| } else { |
| // Hairline case. The scale and skew already happened before tessellation. |
| args.fVertBuilder->codeAppend(R"( |
| float2 devCoord = strokeCoord + TRANSLATE; |
| float2 localCoord = inverse(AFFINE_MATRIX) * strokeCoord;)"); |
| gpArgs->fPositionVar.set(kFloat2_GrSLType, "devCoord"); |
| gpArgs->fLocalCoordVar.set(kFloat2_GrSLType, "localCoord"); |
| } |
| |
| if (!shader.hasDynamicColor()) { |
| // The fragment shader just outputs a uniform color. |
| const char* colorUniformName; |
| fColorUniform = args.fUniformHandler->addUniform( |
| nullptr, kFragment_GrShaderFlag, kHalf4_GrSLType, "color", &colorUniformName); |
| args.fFragBuilder->codeAppendf("half4 %s = %s;", args.fOutputColor, colorUniformName); |
| } else { |
| // Color gets passed in through an instance attrib. |
| args.fFragBuilder->codeAppendf("half4 %s;", args.fOutputColor); |
| args.fVaryingHandler->addPassThroughAttribute( |
| shader.fAttribs.back(), args.fOutputColor, |
| GrGLSLVaryingHandler::Interpolation::kCanBeFlat); |
| } |
| args.fFragBuilder->codeAppendf("const half4 %s = half4(1);", args.fOutputCoverage); |
| } |
| |
| void setData(const GrGLSLProgramDataManager& pdman, |
| const GrGeometryProcessor& geomProc) override { |
| const auto& shader = geomProc.cast<GrStrokeTessellateShader>(); |
| const auto& stroke = shader.fStroke; |
| |
| if (!shader.hasDynamicStroke()) { |
| // Set up the tessellation control uniforms. |
| GrStrokeTolerances tolerances; |
| if (!stroke.isHairlineStyle()) { |
| tolerances = GrStrokeTolerances::MakeNonHairline(shader.viewMatrix().getMaxScale(), |
| stroke.getWidth()); |
| } else { |
| // In the hairline case we transform prior to tessellation. Set up tolerances for an |
| // identity viewMatrix and a strokeWidth of 1. |
| tolerances = GrStrokeTolerances::MakeNonHairline(1, 1); |
| } |
| float strokeRadius = (stroke.isHairlineStyle()) ? .5f : stroke.getWidth() * .5; |
| pdman.set4f(fTessControlArgsUniform, |
| tolerances.fParametricIntolerance, // PARAMETRIC_INTOLERANCE |
| tolerances.fNumRadialSegmentsPerRadian, // NUM_RADIAL_SEGMENTS_PER_RADIAN |
| GetJoinType(shader.fStroke), // JOIN_TYPE |
| strokeRadius); // STROKE_RADIUS |
| } else { |
| SkASSERT(!stroke.isHairlineStyle()); |
| float maxScale = shader.viewMatrix().getMaxScale(); |
| pdman.set1f(fTessControlArgsUniform, |
| GrStrokeTolerances::CalcParametricIntolerance(maxScale)); |
| } |
| |
| // Set up the view matrix, if any. |
| const SkMatrix& m = shader.viewMatrix(); |
| if (!m.isIdentity()) { |
| pdman.set2f(fTranslateUniform, m.getTranslateX(), m.getTranslateY()); |
| pdman.set4f(fAffineMatrixUniform, m.getScaleX(), m.getSkewY(), m.getSkewX(), |
| m.getScaleY()); |
| } |
| |
| if (!shader.hasDynamicColor()) { |
| pdman.set4fv(fColorUniform, 1, shader.fColor.vec()); |
| } |
| } |
| |
| GrGLSLUniformHandler::UniformHandle fTessControlArgsUniform; |
| GrGLSLUniformHandler::UniformHandle fTranslateUniform; |
| GrGLSLUniformHandler::UniformHandle fAffineMatrixUniform; |
| GrGLSLUniformHandler::UniformHandle fColorUniform; |
| }; |
| |
| void GrStrokeTessellateShader::getGLSLProcessorKey(const GrShaderCaps&, |
| GrProcessorKeyBuilder* b) const { |
| bool keyNeedsJoin = (fMode == Mode::kIndirect) && !(fShaderFlags & ShaderFlags::kDynamicStroke); |
| SkASSERT(fStroke.getJoin() >> 2 == 0); |
| // Attribs get worked into the key automatically during GrGeometryProcessor::getAttributeKey(). |
| // When color is in a uniform, it's always wide. kWideColor doesn't need to be considered here. |
| uint32_t key = (uint32_t)(fShaderFlags & ~ShaderFlags::kWideColor); |
| key = (key << 1) | (uint32_t)fMode; |
| key = (key << 2) | ((keyNeedsJoin) ? fStroke.getJoin() : 0); |
| key = (key << 1) | (uint32_t)fStroke.isHairlineStyle(); |
| key = (key << 1) | (uint32_t)this->viewMatrix().isIdentity(); |
| b->add32(key); |
| } |
| |
| GrGLSLGeometryProcessor* GrStrokeTessellateShader::createGLSLInstance(const GrShaderCaps&) const { |
| return (fMode == Mode::kTessellation) ? (GrGLSLGeometryProcessor*)new TessellationImpl |
| : new IndirectImpl; |
| } |
