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Changes to make 2pt gradient source code better aligned with our future doc

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See https://skia-review.googlesource.com/c/skia/+/89340 for the doc

Bug: skia:
Change-Id: I7a57eea317bbc424278c9eaa524a6b7e3b36178e
Reviewed-on: https://skia-review.googlesource.com/90203
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Yuqian Li <liyuqian@google.com>
This commit is contained in:
Yuqian Li 2018-01-02 13:10:19 -05:00 committed by Skia Commit-Bot
parent df6290ce03
commit ad8b489f9e
1 changed files with 23 additions and 24 deletions
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47
src/shaders/gradients/SkTwoPointConicalGradient_gpu.cpp
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@ -17,6 +17,7 @@
// For brevity
typedef GrGLSLProgramDataManager::UniformHandle UniformHandle;
// Please see https://skia.org/dev/design/conical for how our shader works.
class TwoPointConicalEffect : public GrGradientEffect {
public:
class DegeneratedGLSLProcessor; // radial (center0 == center1) or strip (r0 == r1) case
@ -300,6 +301,7 @@ private:
// FocalGLSLProcessor
//////////////////////////////////////////////////////////////////////////////
// Please see https://skia.org/dev/design/conical for how our shader works.
class TwoPointConicalEffect::FocalGLSLProcessor : public GrGradientEffect::GLSLProcessor {
protected:
void emitCode(EmitArgs& args) override {
@ -320,48 +322,44 @@ protected:
const char* p = coords2D.c_str();
if (ge.isFocalOnCircle()) {
fragBuilder->codeAppendf("half %s_prime = dot(%s, %s) / %s.x;", tName, p, p, p);
fragBuilder->codeAppendf("half x_t = dot(%s, %s) / %s.x;", p, p, p);
} else if (ge.isWellBehaved()) {
// empty sign is positive
char sign = ge.isRadiusIncreasing() ? ' ' : '-';
fragBuilder->codeAppendf("half %s_prime = %clength(%s) - %s.x * %s;",
tName, sign, p, p, p0.c_str());
fragBuilder->codeAppendf("half x_t = length(%s) - %s.x * %s;", p, p, p0.c_str());
} else {
char sign = ge.isSwapped() ? '-' : ' ';
char sign = (ge.isSwapped() || !ge.isRadiusIncreasing()) ? '-' : ' ';
fragBuilder->codeAppendf("half temp = %s.x * %s.x - %s.y * %s.y;", p, p, p, p);
// Initialize t_prime to illegal state (where r(t) < 0)
fragBuilder->codeAppendf("half %s_prime = %s;",
tName, ge.isRadiusIncreasing() ? "-1" : "1");
// Initialize x_t to illegal state
fragBuilder->codeAppendf("half x_t = -1;");
// Only do sqrt if temp >= 0; this is significantly slower than checking temp >= 0 in
// the if statement that checks r(t) >= 0. But GPU may break if we sqrt a negative
// float. (Although I havevn't observed that on any devices so far, and the old approach
// also does sqrt negative value without a check.) If the performance is really
// critical, maybe we should just compute the area where temp and t_prime are always
// critical, maybe we should just compute the area where temp and x_t are always
// valid and drop all these ifs.
fragBuilder->codeAppendf("if (temp >= 0) {");
fragBuilder->codeAppendf("%s_prime = (%csqrt(temp) - %s.x * %s);",
tName, sign, p, p0.c_str());
fragBuilder->codeAppendf("x_t = (%csqrt(temp) - %s.x * %s);", sign, p, p0.c_str());
fragBuilder->codeAppendf("}");
}
// "- 0" is much faster than "- p1" so we specialize the natively focal case where p1 = 0.
fragBuilder->codeAppendf("half %s = %s_prime - %s;", tName, tName,
ge.isNativelyFocal() ? "0" : p1.c_str());
if (ge.isSwapped()) {
fragBuilder->codeAppendf("%s = 1 - %s;", tName, tName);
}
// empty sign is positive
char sign = ge.isRadiusIncreasing() ? ' ' : '-';
// "- 0" is much faster than "- p1" so we specialize the natively focal case where p1 = 0.
fragBuilder->codeAppendf("half %s = %cx_t - %s;", tName, sign,
ge.isNativelyFocal() ? "0" : p1.c_str());
if (!ge.isWellBehaved()) {
// output will default to transparent black (we simply won't write anything
// else to it if invalid, instead of discarding or returning prematurely)
fragBuilder->codeAppendf("%s = half4(0.0,0.0,0.0,0.0);", args.fOutputColor);
// r(t) must be nonnegative; we need to swap direction if r0 > r1 because we did a final
// scale of r1 / (r1 - r0) that's negative if r0 > r1.
char direction = ge.isRadiusIncreasing() ? '>' : '<';
fragBuilder->codeAppendf("if (%s_prime %c= 0.0) {", tName, direction);
fragBuilder->codeAppendf("if (x_t > 0.0) {");
}
if (ge.isSwapped()) {
fragBuilder->codeAppendf("%s = 1 - %s;", tName, tName);
}
this->emitColor(fragBuilder,
uniformHandler,
args.fShaderCaps,
@ -496,7 +494,8 @@ TwoPointConicalEffect::Data::Data(const SkTwoPointConicalGradient& shader, SkMat
} else {
matrix.postScale(r1 / (r1 * r1 - 1), 1 / sqrt(SkScalarAbs(r1 * r1 - 1)));
}
matrix.postScale(r1 / (r1 - r0), r1 / (r1 - r0));
SkScalar scale = SkScalarAbs(r1 / (r1 - r0)); // |1 - f|
matrix.postScale(scale, scale);
}
}
}