C++ GrGLSLFragmentBuilder::fragmentPosition方法代码示例

void GrGLConvexPolyEffect::emitCode(EmitArgs& args) {
    const GrConvexPolyEffect& cpe = args.fFp.cast<GrConvexPolyEffect>();

    const char *edgeArrayName;
    fEdgeUniform = args.fUniformHandler->addUniformArray(GrGLSLUniformHandler::kFragment_Visibility,
                                                         kVec3f_GrSLType,
                                                         kDefault_GrSLPrecision,
                                                         "edges",
                                                         cpe.getEdgeCount(),
                                                         &edgeArrayName);
    GrGLSLFragmentBuilder* fragBuilder = args.fFragBuilder;
    fragBuilder->codeAppend("\t\tfloat alpha = 1.0;\n");
    fragBuilder->codeAppend("\t\tfloat edge;\n");
    const char* fragmentPos = fragBuilder->fragmentPosition();
    for (int i = 0; i < cpe.getEdgeCount(); ++i) {
        fragBuilder->codeAppendf("\t\tedge = dot(%s[%d], vec3(%s.x, %s.y, 1));\n",
                                 edgeArrayName, i, fragmentPos, fragmentPos);
        if (GrProcessorEdgeTypeIsAA(cpe.getEdgeType())) {
            fragBuilder->codeAppend("\t\tedge = clamp(edge, 0.0, 1.0);\n");
        } else {
            fragBuilder->codeAppend("\t\tedge = edge >= 0.5 ? 1.0 : 0.0;\n");
        }
        fragBuilder->codeAppend("\t\talpha *= edge;\n");
    }

    if (GrProcessorEdgeTypeIsInverseFill(cpe.getEdgeType())) {
        fragBuilder->codeAppend("\talpha = 1.0 - alpha;\n");
    }
    fragBuilder->codeAppendf("\t%s = %s;\n", args.fOutputColor,
                             (GrGLSLExpr4(args.fInputColor) * GrGLSLExpr1("alpha")).c_str());
}

void GLDitherEffect::emitCode(EmitArgs& args) {
    GrGLSLFragmentBuilder* fragBuilder = args.fFragBuilder;
    // Generate a random number based on the fragment position. For this
    // random number generator, we use the "GLSL rand" function
    // that seems to be floating around on the internet. It works under
    // the assumption that sin(<big number>) oscillates with high frequency
    // and sampling it will generate "randomness". Since we're using this
    // for rendering and not cryptography it should be OK.

    // For each channel c, add the random offset to the pixel to either bump
    // it up or let it remain constant during quantization.
    fragBuilder->codeAppendf("\t\tfloat r = "
                             "fract(sin(dot(%s.xy ,vec2(12.9898,78.233))) * 43758.5453);\n",
                             fragBuilder->fragmentPosition());
    fragBuilder->codeAppendf("\t\t%s = (1.0/255.0) * vec4(r, r, r, r) + %s;\n",
                             args.fOutputColor, GrGLSLExpr4(args.fInputColor).c_str());
}

        void onEmitCode(EmitArgs& args, GrGPArgs* gpArgs) override {
            const PLSQuadEdgeEffect& qe = args.fGP.cast<PLSQuadEdgeEffect>();
            GrGLSLVertexBuilder* vsBuilder = args.fVertBuilder;
            GrGLSLVaryingHandler* varyingHandler = args.fVaryingHandler;
            GrGLSLUniformHandler* uniformHandler = args.fUniformHandler;

            // emit attributes
            varyingHandler->emitAttributes(qe);

            GrGLSLVertToFrag uv(kVec2f_GrSLType);
            varyingHandler->addVarying("uv", &uv, kHigh_GrSLPrecision);
            vsBuilder->codeAppendf("%s = %s;", uv.vsOut(), qe.inUV()->fName);

            GrGLSLVertToFrag ep1(kVec2f_GrSLType);
            varyingHandler->addVarying("endpoint1", &ep1, kHigh_GrSLPrecision);
            vsBuilder->codeAppendf("%s = vec2(%s.x, %s.y);", ep1.vsOut(), 
                                  qe.inEndpoint1()->fName, qe.inEndpoint1()->fName);

            GrGLSLVertToFrag ep2(kVec2f_GrSLType);
            varyingHandler->addVarying("endpoint2", &ep2, kHigh_GrSLPrecision);
            vsBuilder->codeAppendf("%s = vec2(%s.x, %s.y);", ep2.vsOut(), 
                                  qe.inEndpoint2()->fName, qe.inEndpoint2()->fName);

            GrGLSLVertToFrag delta(kVec2f_GrSLType);
            varyingHandler->addVarying("delta", &delta, kHigh_GrSLPrecision);
            vsBuilder->codeAppendf("%s = vec2(%s.x - %s.x, %s.y - %s.y) * 0.5;", 
                                   delta.vsOut(), ep1.vsOut(), ep2.vsOut(), ep2.vsOut(), 
                                   ep1.vsOut());

            GrGLSLVertToFrag windings(kInt_GrSLType);
            varyingHandler->addFlatVarying("windings", &windings, kLow_GrSLPrecision);
            vsBuilder->codeAppendf("%s = %s;", 
                                   windings.vsOut(), qe.inWindings()->fName);

            // Setup position
            this->setupPosition(vsBuilder, gpArgs, qe.inPosition()->fName);

            // emit transforms
            this->emitTransforms(vsBuilder, varyingHandler, uniformHandler, gpArgs->fPositionVar, 
                                 qe.inPosition()->fName, qe.localMatrix(), args.fTransformsIn, 
                                 args.fTransformsOut);

            GrGLSLFragmentBuilder* fsBuilder = args.fFragBuilder;
            SkAssertResult(fsBuilder->enableFeature(
                           GrGLSLFragmentShaderBuilder::kPixelLocalStorage_GLSLFeature));
            SkAssertResult(fsBuilder->enableFeature(
                    GrGLSLFragmentShaderBuilder::kStandardDerivatives_GLSLFeature));
            static const int QUAD_ARGS = 2;
            GrGLSLShaderVar inQuadArgs[QUAD_ARGS] = {
                GrGLSLShaderVar("dot", kFloat_GrSLType, 0, kHigh_GrSLPrecision),
                GrGLSLShaderVar("uv", kVec2f_GrSLType, 0, kHigh_GrSLPrecision)
            };
            SkString inQuadName;

            const char* inQuadCode = "if (uv.x * uv.x <= uv.y) {"
                                     "return dot >= 0.0;"
                                     "} else {"
                                     "return false;"
                                     "}";
            fsBuilder->emitFunction(kBool_GrSLType, "in_quad", QUAD_ARGS, inQuadArgs, inQuadCode, 
                                    &inQuadName);
            fsBuilder->declAppendf(GR_GL_PLS_PATH_DATA_DECL);
            // keep the derivative instructions outside the conditional
            fsBuilder->codeAppendf("highp vec2 uvdX = dFdx(%s);", uv.fsIn());
            fsBuilder->codeAppendf("highp vec2 uvdY = dFdy(%s);", uv.fsIn());
            fsBuilder->codeAppend("highp vec2 uvIncX = uvdX * 0.45 + uvdY * -0.1;");
            fsBuilder->codeAppend("highp vec2 uvIncY = uvdX * 0.1 + uvdY * 0.55;");
            fsBuilder->codeAppendf("highp vec2 uv = %s.xy - uvdX * 0.35 - uvdY * 0.25;", 
                                   uv.fsIn());
            fsBuilder->codeAppendf("highp vec2 firstSample = %s.xy - vec2(0.25);",
                                   fsBuilder->fragmentPosition());
            fsBuilder->codeAppendf("highp float d = dot(%s, (firstSample - %s).yx) * 2.0;", 
                                   delta.fsIn(), ep1.fsIn());
            fsBuilder->codeAppendf("pls.windings[0] += %s(d, uv) ? %s : 0;", inQuadName.c_str(), 
                                   windings.fsIn());
            fsBuilder->codeAppend("uv += uvIncX;");
            fsBuilder->codeAppendf("d += %s.x;", delta.fsIn());
            fsBuilder->codeAppendf("pls.windings[1] += %s(d, uv) ? %s : 0;", inQuadName.c_str(), 
                                   windings.fsIn());
            fsBuilder->codeAppend("uv += uvIncY;");
            fsBuilder->codeAppendf("d += %s.y;", delta.fsIn());
            fsBuilder->codeAppendf("pls.windings[2] += %s(d, uv) ? %s : 0;", inQuadName.c_str(), 
                                   windings.fsIn());
            fsBuilder->codeAppend("uv -= uvIncX;");
            fsBuilder->codeAppendf("d -= %s.x;", delta.fsIn());
            fsBuilder->codeAppendf("pls.windings[3] += %s(d, uv) ? %s : 0;", inQuadName.c_str(), 
                                   windings.fsIn());
        }

void GLEllipticalRRectEffect::emitCode(EmitArgs& args) {
    const EllipticalRRectEffect& erre = args.fFp.cast<EllipticalRRectEffect>();
    const char *rectName;
    // The inner rect is the rrect bounds inset by the x/y radii
    fInnerRectUniform = args.fBuilder->addUniform(GrGLSLProgramBuilder::kFragment_Visibility,
                                            kVec4f_GrSLType, kDefault_GrSLPrecision,
                                            "innerRect",
                                            &rectName);

    GrGLSLFragmentBuilder* fragBuilder = args.fFragBuilder;
    const char* fragmentPos = fragBuilder->fragmentPosition();
    // At each quarter-ellipse corner we compute a vector that is the offset of the fragment pos
    // to the ellipse center. The vector is pinned in x and y to be in the quarter-plane relevant
    // to that corner. This means that points near the interior near the rrect top edge will have
    // a vector that points straight up for both the TL left and TR corners. Computing an
    // alpha from this vector at either the TR or TL corner will give the correct result. Similarly,
    // fragments near the other three edges will get the correct AA. Fragments in the interior of
    // the rrect will have a (0,0) vector at all four corners. So long as the radii > 0.5 they will
    // correctly produce an alpha value of 1 at all four corners. We take the min of all the alphas.
    //
    // The code below is a simplified version of the above that performs maxs on the vector
    // components before computing distances and alpha values so that only one distance computation
    // need be computed to determine the min alpha.
    fragBuilder->codeAppendf("\t\tvec2 dxy0 = %s.xy - %s.xy;\n", rectName, fragmentPos);
    fragBuilder->codeAppendf("\t\tvec2 dxy1 = %s.xy - %s.zw;\n", fragmentPos, rectName);
    // The uniforms with the inv squared radii are highp to prevent underflow.
    switch (erre.getRRect().getType()) {
        case SkRRect::kSimple_Type: {
            const char *invRadiiXYSqdName;
            fInvRadiiSqdUniform = args.fBuilder->addUniform(
                                                         GrGLSLProgramBuilder::kFragment_Visibility,
                                                         kVec2f_GrSLType, kHigh_GrSLPrecision,
                                                         "invRadiiXY",
                                                         &invRadiiXYSqdName);
            fragBuilder->codeAppend("\t\tvec2 dxy = max(max(dxy0, dxy1), 0.0);\n");
            // Z is the x/y offsets divided by squared radii.
            fragBuilder->codeAppendf("\t\tvec2 Z = dxy * %s;\n", invRadiiXYSqdName);
            break;
        }
        case SkRRect::kNinePatch_Type: {
            const char *invRadiiLTRBSqdName;
            fInvRadiiSqdUniform = args.fBuilder->addUniform(
                                                         GrGLSLProgramBuilder::kFragment_Visibility,
                                                         kVec4f_GrSLType, kHigh_GrSLPrecision,
                                                         "invRadiiLTRB",
                                                         &invRadiiLTRBSqdName);
            fragBuilder->codeAppend("\t\tvec2 dxy = max(max(dxy0, dxy1), 0.0);\n");
            // Z is the x/y offsets divided by squared radii. We only care about the (at most) one
            // corner where both the x and y offsets are positive, hence the maxes. (The inverse
            // squared radii will always be positive.)
            fragBuilder->codeAppendf("\t\tvec2 Z = max(max(dxy0 * %s.xy, dxy1 * %s.zw), 0.0);\n",
                                     invRadiiLTRBSqdName, invRadiiLTRBSqdName);
            break;
        }
        default:
            SkFAIL("RRect should always be simple or nine-patch.");
    }
    // implicit is the evaluation of (x/a)^2 + (y/b)^2 - 1.
    fragBuilder->codeAppend("\t\tfloat implicit = dot(Z, dxy) - 1.0;\n");
    // grad_dot is the squared length of the gradient of the implicit.
    fragBuilder->codeAppendf("\t\tfloat grad_dot = 4.0 * dot(Z, Z);\n");
    // avoid calling inversesqrt on zero.
    fragBuilder->codeAppend("\t\tgrad_dot = max(grad_dot, 1.0e-4);\n");
    fragBuilder->codeAppendf("\t\tfloat approx_dist = implicit * inversesqrt(grad_dot);\n");

    if (kFillAA_GrProcessorEdgeType == erre.getEdgeType()) {
        fragBuilder->codeAppend("\t\tfloat alpha = clamp(0.5 - approx_dist, 0.0, 1.0);\n");
    } else {
        fragBuilder->codeAppend("\t\tfloat alpha = clamp(0.5 + approx_dist, 0.0, 1.0);\n");
    }

    fragBuilder->codeAppendf("\t\t%s = %s;\n", args.fOutputColor,
                             (GrGLSLExpr4(args.fInputColor) * GrGLSLExpr1("alpha")).c_str());
}