1 INPUT mediump vec2 vPosition;
2 INPUT mediump vec2 vRectSize;
3 INPUT mediump float vCornerRadius;
5 uniform lowp vec4 uColor;
6 uniform lowp vec3 mixColor;
7 uniform mediump float blurRadius;
11 OUT_COLOR = vec4(mixColor, 1.0) * uColor;
13 mediump vec2 v = abs(vPosition) - vRectSize;
14 mediump float cy = vCornerRadius + blurRadius;
15 mediump float cr = vCornerRadius + blurRadius;
17 cy = min(cy, min(vRectSize.x, vRectSize.y));
18 v = vec2(min(v.x, v.y), max(v.x, v.y));
21 mediump float blur = 1.0;
22 mediump float potential = 0.0;
23 mediump float alias = min(vCornerRadius, 1.0);
24 mediump float potentialMin = cy + vCornerRadius - blurRadius - alias;
25 mediump float potentialMax = cy + vCornerRadius + blurRadius + alias;
27 // move center of circles for reduce defact
28 mediump float cyDiff = min(cy, 0.2 * blurRadius);
32 mediump float diffFromBaseline = cy * v.y - (cy + cr) * v.x;
34 if(diffFromBaseline > 0.0)
36 // out of calculation bound.
39 // for anti-alias when blurRaidus = 0.0
40 mediump float heuristicBaselineScale = max(1.0 , cr * (cr + cy));
41 mediump float potentialDiff = min(alias, diffFromBaseline / heuristicBaselineScale);
42 potentialMin += potentialDiff;
43 potentialMax -= potentialDiff;
47 // get some circle centered (x, x) and radius (r = cr / cy * x)
48 // s.t. point v is on that circle
49 // highest point of that circle is (x, x + r) and potential is x + r
51 // solve (v.x - x)^2 + (v.y - x)^2 = (cr / cy * x)^2
53 mediump float A = (cr * cr - 2.0 * cy * cy);
54 mediump float B = cy * (v.x + v.y);
55 mediump float V = dot(v,v);
56 mediump float D = B * B + A * V;
57 potential = V * (cr + cy) / (sqrt(D) + B);
60 blur = 1.0 - smoothstep(potentialMin, potentialMax, potential);