diff options
author | 2013-08-01 17:09:11 +0000 | |
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committer | 2013-08-01 17:09:11 +0000 | |
commit | 3f2a2d5fdc833dd20900ee90249b03474d0e00b3 (patch) | |
tree | 9d608b97c2eb2a83f12bd2204c1b18483e11280a | |
parent | 7fb83c8c72f2a035e84a4ee4ee6abcf5a4872166 (diff) |
Add Loop Blinn hairline conics to GPU
BUG=
R=bsalomon@google.com
Review URL: https://codereview.chromium.org/21036008
git-svn-id: http://skia.googlecode.com/svn/trunk@10487 2bbb7eff-a529-9590-31e7-b0007b416f81
-rw-r--r-- | samplecode/SampleHairCurves.cpp | 22 | ||||
-rw-r--r-- | src/gpu/GrAAHairLinePathRenderer.cpp | 236 |
2 files changed, 167 insertions, 91 deletions
diff --git a/samplecode/SampleHairCurves.cpp b/samplecode/SampleHairCurves.cpp index 183fc10995..2cf0b3c900 100644 --- a/samplecode/SampleHairCurves.cpp +++ b/samplecode/SampleHairCurves.cpp @@ -35,6 +35,7 @@ protected: canvas->save(); canvas->scale(1000 * SK_Scalar1, 1000 * SK_Scalar1); SkRandom rand; + SkRandom randW; SkPath curves; SkPath hulls; SkPath ctrlPts; @@ -82,6 +83,27 @@ protected: SkScalar pts[] = { rand.nextUScalar1(), rand.nextUScalar1(), rand.nextUScalar1(), rand.nextUScalar1(), + rand.nextUScalar1(), rand.nextUScalar1(), + }; + SkScalar weight = randW.nextUScalar1() * 2.0f; + + curves.moveTo(pts[0], pts[1]); + curves.conicTo(pts[2], pts[3], + pts[4], pts[5], + weight); + + hulls.moveTo(pts[0], pts[1]); + hulls.lineTo(pts[2], pts[3]); + hulls.lineTo(pts[4], pts[5]); + + ctrlPts.addCircle(pts[0], pts[1], SK_Scalar1 / 200); + ctrlPts.addCircle(pts[2], pts[3], SK_Scalar1 / 200); + ctrlPts.addCircle(pts[4], pts[5], SK_Scalar1 / 200); + } + for (int i = 0; i < 100; ++i) { + SkScalar pts[] = { + rand.nextUScalar1(), rand.nextUScalar1(), + rand.nextUScalar1(), rand.nextUScalar1(), }; curves.moveTo(pts[0], pts[1]); curves.lineTo(pts[2], pts[3]); diff --git a/src/gpu/GrAAHairLinePathRenderer.cpp b/src/gpu/GrAAHairLinePathRenderer.cpp index 67c2a32863..ecd938961e 100644 --- a/src/gpu/GrAAHairLinePathRenderer.cpp +++ b/src/gpu/GrAAHairLinePathRenderer.cpp @@ -1,4 +1,3 @@ - /* * Copyright 2011 Google Inc. * @@ -146,9 +145,9 @@ int get_float_exp(float x) { // Uses the max curvature function for quads to estimate // where to chop the conic. If the max curvature is not // found along the curve segment it will return 1 and -// dst[0] is the orginal conic. If it returns 2 the dst[0] +// dst[0] is the original conic. If it returns 2 the dst[0] // and dst[1] are the two new conics. -int chop_conic(const SkPoint src[3], SkConic dst[2], const SkScalar weight) { +int split_conic(const SkPoint src[3], SkConic dst[2], const SkScalar weight) { SkScalar t = SkFindQuadMaxCurvature(src); if (t == 0) { if (dst) { @@ -165,6 +164,21 @@ int chop_conic(const SkPoint src[3], SkConic dst[2], const SkScalar weight) { } } +// Calls split_conic on the entire conic and then once more on each subsection. +// Most cases will result in either 1 conic (chop point is not within t range) +// or 3 points (split once and then one subsection is split again). +int chop_conic(const SkPoint src[3], SkConic dst[4], const SkScalar weight) { + SkConic dstTemp[2]; + int conicCnt = split_conic(src, dstTemp, weight); + if (2 == conicCnt) { + int conicCnt2 = split_conic(dstTemp[0].fPts, dst, dstTemp[0].fW); + conicCnt = conicCnt2 + split_conic(dstTemp[1].fPts, &dst[conicCnt2], dstTemp[1].fW); + } else { + dst[0] = dstTemp[0]; + } + return conicCnt; +} + // returns 0 if quad/conic is degen or close to it // in this case approx the path with lines // otherwise returns 1 @@ -271,7 +285,10 @@ int generate_lines_and_quads(const SkPath& path, SkPath::Verb verb = iter.next(pathPts); switch (verb) { case SkPath::kConic_Verb: { - SkConic dst[2]; + SkConic dst[4]; + // We chop the conics to create tighter clipping to hide error + // that appears near max curvature of very thin conics. Thin + // hyperbolas with high weight still show error. int conicCnt = chop_conic(pathPts, dst, iter.conicWeight()); for (int i = 0; i < conicCnt; ++i) { SkPoint* chopPnts = dst[i].fPts; @@ -424,21 +441,18 @@ struct Vertex { SkScalar fC; } fLine; struct { - SkScalar fA; - SkScalar fB; - SkScalar fC; - SkScalar fD; - SkScalar fE; - SkScalar fF; + SkScalar fK; + SkScalar fL; + SkScalar fM; } fConic; GrVec fQuadCoord; struct { - SkScalar fBogus[6]; + SkScalar fBogus[4]; }; }; }; -GR_STATIC_ASSERT(sizeof(Vertex) == 4 * sizeof(GrPoint)); +GR_STATIC_ASSERT(sizeof(Vertex) == 3 * sizeof(GrPoint)); void intersect_lines(const SkPoint& ptA, const SkVector& normA, const SkPoint& ptB, const SkVector& normB, @@ -538,43 +552,67 @@ void bloat_quad(const SkPoint qpts[3], const SkMatrix* toDevice, DevToUV.apply<kVertsPerQuad, sizeof(Vertex), sizeof(GrPoint)>(verts); } +// Input: +// Three control points: p[0], p[1], p[2] and weight: w +// Output: +// Let: +// l = (2*w * (y1 - y0), 2*w * (x0 - x1), 2*w * (x1*y0 - x0*y1)) +// m = (2*w * (y2 - y1), 2*w * (x1 - x2), 2*w * (x2*y1 - x1*y2)) +// k = (y2 - y0, x0 - x2, (x2 - x0)*y0 - (y2 - y0)*x0 ) +void calc_conic_klm(const SkPoint p[3], const SkScalar weight, + SkScalar k[3], SkScalar l[3], SkScalar m[3]) { + const SkScalar w2 = 2 * weight; + l[0] = w2 * (p[1].fY - p[0].fY); + l[1] = w2 * (p[0].fX - p[1].fX); + l[2] = w2 * (p[1].fX * p[0].fY - p[0].fX * p[1].fY); + + m[0] = w2 * (p[2].fY - p[1].fY); + m[1] = w2 * (p[1].fX - p[2].fX); + m[2] = w2 * (p[2].fX * p[1].fY - p[1].fX * p[2].fY); + + k[0] = p[2].fY - p[0].fY; + k[1] = p[0].fX - p[2].fX; + k[2] = (p[2].fX - p[0].fX) * p[0].fY - (p[2].fY - p[0].fY) * p[0].fX; + + // scale the max absolute value of coeffs to 10 + SkScalar scale = 0.0f; + for (int i = 0; i < 3; ++i) { + scale = SkMaxScalar(scale, SkScalarAbs(k[i])); + scale = SkMaxScalar(scale, SkScalarAbs(l[i])); + scale = SkMaxScalar(scale, SkScalarAbs(m[i])); + } + GrAssert(scale > 0); + scale /= 10.0f; + k[0] /= scale; + k[1] /= scale; + k[2] /= scale; + l[0] /= scale; + l[1] /= scale; + l[2] /= scale; + m[0] /= scale; + m[1] /= scale; + m[2] /= scale; +} +// Equations based off of Loop-Blinn Quadratic GPU Rendering // Input Parametric: // P(t) = (P0*(1-t)^2 + 2*w*P1*t*(1-t) + P2*t^2) / (1-t)^2 + 2*w*t*(1-t) + t^2) // Output Implicit: -// Ax^2 + Bxy + Cy^2 + Dx + Ey + F = 0 -// A = 4w^2*(y0-y1)(y1-y2)-(y0-y2)^2 -// B = 4w^2*((x0-x1)(y2-y1)+(x1-x2)(y1-y0)) + 2(x0-x2)(y0-y2) -// C = 4w^2(x0-x1)(x1-x2) - (x0-x2)^2 -// D = 4w^2((x0y1-x1y0)(y1-y2)+(x1y2-x2y1)(y0-y1)) + 2(y2-y0)(x0y2-x2y0) -// E = 4w^2((y0x1-y1x0)(x1-x2)+(y1x2-y2x1)(x0-x1)) + 2(x2-x0)(y0x2-y2x0) -// F = 4w^2(x1y2-x2y1)(x0y1-x1y0) - (x2y0-x0y2)^2 - +// f(x, y, w) = f(P) = K^2 - LM +// K = dot(k, P), L = dot(l, P), M = dot(m, P) +// k, l, m are calculated in function calc_conic_klm void set_conic_coeffs(const SkPoint p[3], Vertex verts[kVertsPerQuad], const float weight) { - const float ww4 = 4 * weight * weight; - const float x0Mx1 = p[0].fX - p[1].fX; - const float x1Mx2 = p[1].fX - p[2].fX; - const float x0Mx2 = p[0].fX - p[2].fX; - const float y0My1 = p[0].fY - p[1].fY; - const float y1My2 = p[1].fY - p[2].fY; - const float y0My2 = p[0].fY - p[2].fY; - const float x0y1Mx1y0 = p[0].fX*p[1].fY - p[1].fX*p[0].fY; - const float x1y2Mx2y1 = p[1].fX*p[2].fY - p[2].fX*p[1].fY; - const float x0y2Mx2y0 = p[0].fX*p[2].fY - p[2].fX*p[0].fY; - const float a = ww4 * y0My1 * y1My2 - y0My2 * y0My2; - const float b = -ww4 * (x0Mx1 * y1My2 + x1Mx2 * y0My1) + 2 * x0Mx2 * y0My2; - const float c = ww4 * x0Mx1 * x1Mx2 - x0Mx2 * x0Mx2; - const float d = ww4 * (x0y1Mx1y0 * y1My2 + x1y2Mx2y1 * y0My1) - 2 * y0My2 * x0y2Mx2y0; - const float e = -ww4 * (x0y1Mx1y0 * x1Mx2 + x1y2Mx2y1 * x0Mx1) + 2 * x0Mx2 * x0y2Mx2y0; - const float f = ww4 * x1y2Mx2y1 * x0y1Mx1y0 - x0y2Mx2y0 * x0y2Mx2y0; + SkScalar k[3]; + SkScalar l[3]; + SkScalar m[3]; + + calc_conic_klm(p, weight, k, l, m); for (int i = 0; i < kVertsPerQuad; ++i) { - verts[i].fConic.fA = a/f; - verts[i].fConic.fB = b/f; - verts[i].fConic.fC = c/f; - verts[i].fConic.fD = d/f; - verts[i].fConic.fE = e/f; - verts[i].fConic.fF = f/f; + const SkPoint pnt = verts[i].fPos; + verts[i].fConic.fK = pnt.fX * k[0] + pnt.fY * k[1] + k[2]; + verts[i].fConic.fL = pnt.fX * l[0] + pnt.fY * l[1] + l[2]; + verts[i].fConic.fM = pnt.fX * m[0] + pnt.fY * m[1] + m[2]; } } @@ -651,12 +689,47 @@ void add_line(const SkPoint p[2], } /** + * Shader is based off of Loop-Blinn Quadratic GPU Rendering * The output of this effect is a hairline edge for conics. - * Conics specified by implicit equation Ax^2 + Bxy + Cy^2 + Dx + Ey + F = 0. - * A, B, C, D are the first vec4 of vertex attributes and - * E and F are the vec2 attached to 2nd vertex attrribute. + * Conics specified by implicit equation K^2 - LM. + * K, L, and M, are the first three values of the vertex attribute, + * the fourth value is not used. Distance is calculated using a + * first order approximation from the taylor series. * Coverage is max(0, 1-distance). */ + +/** + * Test were also run using a second order distance approximation. + * There were two versions of the second order approx. The first version + * is of roughly the form: + * f(q) = |f(p)| - ||f'(p)||*||q-p|| - ||f''(p)||*||q-p||^2. + * The second is similar: + * f(q) = |f(p)| + ||f'(p)||*||q-p|| + ||f''(p)||*||q-p||^2. + * The exact version of the equations can be found in the paper + * "Distance Approximations for Rasterizing Implicit Curves" by Gabriel Taubin + * + * In both versions we solve the quadratic for ||q-p||. + * Version 1: + * gFM is magnitude of first partials and gFM2 is magnitude of 2nd partials (as derived from paper) + * builder->fsCodeAppend("\t\tedgeAlpha = (sqrt(gFM*gFM+4.0*func*gF2M) - gFM)/(2.0*gF2M);\n"); + * Version 2: + * builder->fsCodeAppend("\t\tedgeAlpha = (gFM - sqrt(gFM*gFM-4.0*func*gF2M))/(2.0*gF2M);\n"); + * + * Also note that 2nd partials of k,l,m are zero + * + * When comparing the two second order approximations to the first order approximations, + * the following results were found. Version 1 tends to underestimate the distances, thus it + * basically increases all the error that we were already seeing in the first order + * approx. So this version is not the one to use. Version 2 has the opposite effect + * and tends to overestimate the distances. This is much closer to what we are + * looking for. It is able to render ellipses (even thin ones) without the need to chop. + * However, it can not handle thin hyperbolas well and thus would still rely on + * chopping to tighten the clipping. Another side effect of the overestimating is + * that the curves become much thinner and "ropey". If all that was ever rendered + * were "not too thin" curves and ellipses then 2nd order may have an advantage since + * only one geometry would need to be rendered. However no benches were run comparing + * chopped first order and non chopped 2nd order. + */ class HairConicEdgeEffect : public GrEffect { public: static GrEffectRef* Create() { @@ -689,38 +762,32 @@ public: const char* outputColor, const char* inputColor, const TextureSamplerArray& samplers) SK_OVERRIDE { - const char *vsCoeffABCDName, *fsCoeffABCDName; - const char *vsCoeffEFName, *fsCoeffEFName; + const char *vsName, *fsName; SkAssertResult(builder->enableFeature( GrGLShaderBuilder::kStandardDerivatives_GLSLFeature)); - builder->addVarying(kVec4f_GrSLType, "ConicCoeffsABCD", - &vsCoeffABCDName, &fsCoeffABCDName); + builder->addVarying(kVec4f_GrSLType, "ConicCoeffs", + &vsName, &fsName); const SkString* attr0Name = builder->getEffectAttributeName(drawEffect.getVertexAttribIndices()[0]); - builder->vsCodeAppendf("\t%s = %s;\n", vsCoeffABCDName, attr0Name->c_str()); - - builder->addVarying(kVec2f_GrSLType, "ConicCoeffsEF", - &vsCoeffEFName, &fsCoeffEFName); - const SkString* attr1Name = - builder->getEffectAttributeName(drawEffect.getVertexAttribIndices()[1]); - builder->vsCodeAppendf("\t%s = %s;\n", vsCoeffEFName, attr1Name->c_str()); - - // Based on Gustavson 2006: "Beyond the Pixel: towards infinite resolution textures" - builder->fsCodeAppendf("\t\tfloat edgeAlpha;\n"); - - builder->fsCodeAppendf("\t\tvec3 uv1 = vec3(%s.xy, 1);\n", builder->fragmentPosition()); - builder->fsCodeAppend("\t\tvec3 u2uvv2 = uv1.xxy * uv1.xyy;\n"); - builder->fsCodeAppendf("\t\tvec3 ABC = %s.xyz;\n", fsCoeffABCDName); - builder->fsCodeAppendf("\t\tvec3 DEF = vec3(%s.w, %s.xy);\n", - fsCoeffABCDName, fsCoeffEFName); - - builder->fsCodeAppend("\t\tfloat dfdx = dot(uv1,vec3(2.0*ABC.x,ABC.y,DEF.x));\n"); - builder->fsCodeAppend("\t\tfloat dfdy = dot(uv1,vec3(ABC.y, 2.0*ABC.z,DEF.y));\n"); - builder->fsCodeAppend("\t\tfloat gF = dfdx*dfdx + dfdy*dfdy;\n"); - builder->fsCodeAppend("\t\tedgeAlpha = dot(ABC,u2uvv2) + dot(DEF,uv1);\n"); - builder->fsCodeAppend("\t\tedgeAlpha = sqrt(edgeAlpha*edgeAlpha / gF);\n"); - builder->fsCodeAppend("\t\tedgeAlpha = max((1.0 - edgeAlpha), 0.0);\n"); + builder->vsCodeAppendf("\t%s = %s;\n", vsName, attr0Name->c_str()); + + builder->fsCodeAppend("\t\tfloat edgeAlpha;\n"); + + builder->fsCodeAppendf("\t\tvec3 dklmdx = dFdx(%s.xyz);\n", fsName); + builder->fsCodeAppendf("\t\tvec3 dklmdy = dFdy(%s.xyz);\n", fsName); + builder->fsCodeAppendf("\t\tfloat dfdx =\n" + "\t\t\t2.0*%s.x*dklmdx.x - %s.y*dklmdx.z - %s.z*dklmdx.y;\n", + fsName, fsName, fsName); + builder->fsCodeAppendf("\t\tfloat dfdy =\n" + "\t\t\t2.0*%s.x*dklmdy.x - %s.y*dklmdy.z - %s.z*dklmdy.y;\n", + fsName, fsName, fsName); + builder->fsCodeAppend("\t\tvec2 gF = vec2(dfdx, dfdy);\n"); + builder->fsCodeAppend("\t\tfloat gFM = sqrt(dot(gF, gF));\n"); + builder->fsCodeAppendf("\t\tfloat func = abs(%s.x*%s.x - %s.y*%s.z);\n", fsName, fsName, + fsName, fsName); + builder->fsCodeAppend("\t\tedgeAlpha = func / gFM;\n"); + builder->fsCodeAppend("\t\tedgeAlpha = max(1.0 - edgeAlpha, 0.0);\n"); // Add line below for smooth cubic ramp // builder->fsCodeAppend("\t\tedgeAlpha = edgeAlpha*edgeAlpha*(3.0-2.0*edgeAlpha);\n"); @@ -742,8 +809,6 @@ public: private: HairConicEdgeEffect() { this->addVertexAttrib(kVec4f_GrSLType); - this->addVertexAttrib(kVec2f_GrSLType); - this->setWillReadFragmentPosition(); } virtual bool onIsEqual(const GrEffect& other) const SK_OVERRIDE { @@ -761,9 +826,8 @@ GrEffectRef* HairConicEdgeEffect::TestCreate(SkMWCRandom* random, GrContext*, const GrDrawTargetCaps& caps, GrTexture*[]) { - return HairConicEdgeEffect::Create(); + return caps.shaderDerivativeSupport() ? HairConicEdgeEffect::Create() : NULL; } -/////////////////////////////////////////////////////////////////////////////// /** * The output of this effect is a hairline edge for quadratics. @@ -965,14 +1029,6 @@ extern const GrVertexAttrib gHairlineAttribs[] = { {kVec2f_GrVertexAttribType, 0, kPosition_GrVertexAttribBinding}, {kVec4f_GrVertexAttribType, sizeof(GrPoint), kEffect_GrVertexAttribBinding} }; - -// Conic -// position + ABCD + EF -extern const GrVertexAttrib gConicVertexAttribs[] = { - { kVec2f_GrVertexAttribType, 0, kPosition_GrVertexAttribBinding }, - { kVec4f_GrVertexAttribType, sizeof(GrPoint), kEffect_GrVertexAttribBinding }, - { kVec2f_GrVertexAttribType, 3*sizeof(GrPoint), kEffect_GrVertexAttribBinding } -}; }; bool GrAAHairLinePathRenderer::createGeom( @@ -1011,7 +1067,7 @@ bool GrAAHairLinePathRenderer::createGeom( int vertCnt = kVertsPerLineSeg * *lineCnt + kVertsPerQuad * *quadCnt + kVertsPerQuad * *conicCnt; - target->drawState()->setVertexAttribs<gConicVertexAttribs>(SK_ARRAY_COUNT(gConicVertexAttribs)); + target->drawState()->setVertexAttribs<gHairlineAttribs>(SK_ARRAY_COUNT(gHairlineAttribs)); GrAssert(sizeof(Vertex) == target->getDrawState().getVertexSize()); if (!arg->set(target, vertCnt, 0)) { @@ -1056,13 +1112,11 @@ bool GrAAHairLinePathRenderer::canDrawPath(const SkPath& path, return false; } - static const uint32_t gReqDerivMask = SkPath::kCubic_SegmentMask | - SkPath::kQuad_SegmentMask; - if (!target->caps()->shaderDerivativeSupport() && - (gReqDerivMask & path.getSegmentMasks())) { - return false; + if (SkPath::kLine_SegmentMask == path.getSegmentMasks() || + target->caps()->shaderDerivativeSupport()) { + return true; } - return true; + return false; } bool GrAAHairLinePathRenderer::onDrawPath(const SkPath& path, |