1 INPUT mediump vec2 vPosition;
2 INPUT mediump vec2 vRectSize;
3 INPUT mediump vec2 vOptRectSize;
4 INPUT mediump vec4 vCornerRadius;
6 uniform lowp vec4 uColor;
7 uniform lowp vec3 mixColor;
8 uniform mediump float blurRadius;
12 OUT_COLOR = vec4(mixColor, 1.0) * uColor;
13 if(abs(vPosition.x) < vOptRectSize.x && abs(vPosition.y) < vOptRectSize.y)
18 mediump float radius =
20 mix(vCornerRadius.x, vCornerRadius.y, sign(vPosition.x) * 0.5 + 0.5),
21 mix(vCornerRadius.w, vCornerRadius.z, sign(vPosition.x) * 0.5 + 0.5),
22 sign(vPosition.y) * 0.5 + 0.5
25 mediump vec2 v = abs(vPosition) - vRectSize + radius;
26 mediump float cy = radius + blurRadius;
27 mediump float cr = radius + blurRadius;
29 cy = min(cy, min(vRectSize.x, vRectSize.y) - radius);
30 v = vec2(min(v.x, v.y), max(v.x, v.y));
33 mediump float blur = 1.0;
34 mediump float potential = 0.0;
35 mediump float alias = min(radius, 1.0);
36 mediump float potentialMin = cy + radius - blurRadius - alias;
37 mediump float potentialMax = cy + radius + blurRadius + alias;
39 // move center of circles for reduce defact
40 mediump float cyDiff = min(cy, 0.2 * blurRadius);
44 mediump float diffFromBaseline = cy * v.y - (cy + cr) * v.x;
46 if(diffFromBaseline > 0.0)
48 // out of calculation bound.
51 // for anti-alias when blurRaidus = 0.0
52 mediump float heuristicBaselineScale = max(1.0 , cr * (cr + cy));
53 mediump float potentialDiff = min(alias, diffFromBaseline / heuristicBaselineScale);
54 potentialMin += potentialDiff;
55 potentialMax -= potentialDiff;
59 // get some circle centered (x, x) and radius (r = cr / cy * x)
60 // s.t. point v is on that circle
61 // highest point of that circle is (x, x + r) and potential is x + r
63 // solve (v.x - x)^2 + (v.y - x)^2 = (cr / cy * x)^2
65 mediump float A = (cr * cr - 2.0 * cy * cy);
66 mediump float B = cy * (v.x + v.y);
67 mediump float V = dot(v,v);
68 mediump float D = B * B + A * V;
69 potential = V * (cr + cy) / (sqrt(D) + B);
72 blur = 1.0 - smoothstep(potentialMin, potentialMax, potential);