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#version 130
out vec4 fragColor;
uniform vec2 res;
uniform float time;
const float sharpness = 300;
const float PI = 3.14159265358979323846;
mat2 rot(float a) {
return mat2(
cos(a), -sin(a),
sin(a), cos(a)
);
}
float poly(float n, vec2 m, float r, float rt, vec2 p) {
vec2 diff = (m - p) * rot(rt);
float d = length(diff);
float alpha = PI / n;
float gamma = mod(abs(atan(diff.x, diff.y)), alpha*2);
if (gamma > alpha)
gamma -= 2*alpha;
float r2 = r * cos(alpha) / cos(gamma);
return clamp((r2 - d)*sharpness, 0.0, 1.0);
}
float poly_d(float n, vec2 m, float r, float rt, vec2 p) {
return poly(n, m, r, rt, p) - poly(n, m, r - 1/sharpness, rt, 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;
float c;
c = poly_d(5 - 3*cos(time/1000), vec2(0, 0), 0.5, PI * time/1000, p);
scene = abs(scene - c);
c = poly_d(5 - 3*cos(time/1000), vec2(0, 0), 0.5, -PI * time/1000, p);
scene = abs(scene - c);
fragColor = vec4(vec3(1, 1, 1) * scene, 1);
}
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