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#version 110
varying vec4 color;
varying vec2 pos;
uniform vec2 center;
uniform float radius;
void main() {
float dist_squared = dot(pos - center, pos - center);
float threshold = 0.8 * radius; // radius border starts at
float thickness = radius - threshold;
if (dist_squared > threshold * threshold && dist_squared < radius * radius) {
float dist = sqrt(dist_squared);
float v = (dist - threshold) / thickness;
v = 2.0 * v - 1.0;
gl_FragColor = color * (1.0 - v * v);
} else {
discard;
}
}
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