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#version 120
#define TWO_PI 6.28318530718
uniform float radius;
uniform vec2 centerPos;
uniform float smoothness;
uniform float value;
vec3 hsv2rgb(vec3 c) {
vec4 K = vec4(1.0, 2.0 / 3.0, 1.0 / 3.0, 3.0);
vec3 p = abs(fract(c.xxx + K.xyz) * 6.0 - K.www);
return c.z * mix(K.xxx, clamp(p - K.xxx, 0.0, 1.0), c.y);
}
void main() {
vec2 stuff = gl_FragCoord.xy - centerPos;
float sdf = length(stuff)-radius;
float saturation = 1.0+(sdf / radius);
float clampd = 1.0 - smoothstep(-smoothness, smoothness, sdf);
float angle = atan(-stuff.x, -stuff.y) / TWO_PI + 0.5;
vec3 col = hsv2rgb(vec3(angle, saturation, value));
gl_FragColor = vec4(col,clampd);
}
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