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#version 130
out vec4 fragColor;
uniform vec2 res;
uniform float time;
const float sharpness = 300;
mat2 rot(float a) {
return mat2(
cos(a), -sin(a),
sin(a), cos(a)
);
}
float circle(vec2 m, float r, vec2 p) {
vec2 diff = m - p;
float d = sqrt(dot(diff, diff));
return clamp((r - d)*sharpness, 0.0, 1.0);
}
float circle_d(vec2 m, float r, vec2 p) {
return circle(m, r, p) - circle(m, r - 1/sharpness, p);
}
void main(void) {
vec2 m = res/2;
float s = min(m.x, m.y);
vec2 p = (gl_FragCoord.xy - m) / s;
float scene = 0;
for (int i = 1; i <= 50; i++) {
float c = circle_d(vec2(0.5, 0) * rot(time/500/i), 0.1 + 0.005*i, p);
scene = abs(scene - c);
}
fragColor = vec4(vec3(1, 1, 1) * scene, 1);
}
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