AuroraMiddleware/skia2
1
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

Add a runtime effect gm for squircle clips

Browse Source 
Change-Id: I6bf9cad2dd7095afbc153e90510dd0f7c398797d
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/382936
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>
This commit is contained in:
Chris Dalton 2021-03-15 10:16:09 -06:00 committed by Skia Commit-Bot
parent fa8133347c
commit 4e94fd11cd
1 changed files with 65 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

65
gm/runtimeshader.cpp
View File

@ -335,6 +335,71 @@ public:
};
DEF_GM(return new DefaultColorRT;)
// Emits coverage for a general superellipse defined by the boundary:
//
// x^m + y^n == 1
//
// Where x and y are normalized coordinates ranging from -1..+1 inside the squircle's bounding box.
//
// See: https://en.wikipedia.org/wiki/Superellipse#Generalizations
class ClipSquircle : public RuntimeShaderGM {
public:
ClipSquircle() : RuntimeShaderGM("clip_squircle", {512, 256}, R"(
uniform float2 exponentsMinus1;
uniform float2x2 derivatives;
half4 main(float2 xy) {
xy = abs(xy);
float2 expMinus1 = pow(xy, exponentsMinus1);
float f = dot(expMinus1, xy) - 1; // f = x^m + y^n - 1
float2 grad = expMinus1 * derivatives;
float fwidth = abs(grad.x) + abs(grad.y);
return half4(saturate(.5 - f/fwidth)); // Approx coverage by riding the gradient to f=0.
}
)") {}
void onDraw(SkCanvas* canvas) override {
SkRect squircle = SkRect::MakeXYWH(7, 3, 300, 185.41f);
float m = 5.32f;
float n = 3.14f;
canvas->save();
canvas->rotate(9.2f, 5, 185);
SkRuntimeShaderBuilder builder(fEffect);
builder.uniform("exponentsMinus1") = SkV2{m - 1, n - 1};
// Calculate a 2x2 "derivatives" matrix that the shader will use to find the gradient.
//
// f = s^m + t^n - 1 [s,t are "squircle" coordinates in normalized -1..+1 space]
//
// gradient = [df/dx df/dy] = [ms^(m-1) nt^(n-1)] * |ds/dx ds/dy|
// |dt/dx dt/dy|
//
// = [s^(m-1) t^(n-1)] * |m 0| * |ds/dx ds/dy|
// |0 n| |dt/dx dt/dy|
//
// = [s^(m-1) t^(n-1)] * |2m/squircleWidth 0| * mat2x2(canvasMatrix)^-1
// |0 2n/squricleHeight|
//
// = [s^(m-1) t^(n-1)] * "derivatives"
//
const SkMatrix& M = canvas->getTotalMatrix();
float a=M.getScaleX(), b=M.getSkewX(), c=M.getSkewY(), d=M.getScaleY();
float determinantTimesHalf = (a*d - b*c) * .5f;
float dx = m / (squircle.width() * determinantTimesHalf);
float dy = n / (squircle.height() * determinantTimesHalf);
builder.uniform("derivatives") = SkV4{d*dx, -c*dy, -b*dx, a*dy};
SkMatrix squircleToLocal;
squircleToLocal.setScaleTranslate(squircle.width()*.5f, squircle.height()*.5f,
squircle.centerX(), squircle.centerY());
canvas->clipShader(builder.makeShader(&squircleToLocal, false));
canvas->clear(SkColorSetARGB(255, 144, 123, 189));
canvas->restore();
}
};
DEF_GM(return new ClipSquircle;)
DEF_SIMPLE_GM(child_sampling_rt, canvas, 256,256) {
static constexpr char scale[] =