61 lines
1.1 KiB
GLSL
61 lines
1.1 KiB
GLSL
#version 120
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#ifdef GL_ES
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precision highp float;
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#endif
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#define PI 3.14159265359
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vec3 pal(in float t, in vec3 a, in vec3 b, in vec3 c, in vec3 d) {
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return a + b*cos(6.28318*(c*t+d));
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}
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uniform vec2 u_resolution;
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uniform vec2 u_mouse;
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uniform float u_time;
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uniform vec2 u_translation;
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uniform float u_scale;
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uniform vec3 u_rgb_1;
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uniform vec3 u_rgb_2;
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uniform vec3 u_rgb_3;
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uniform vec3 u_rgb_4;
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uniform vec2 u_julia_set;
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#define N 256. // Number of iterations?
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#define B 4. // What does B mean?
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float iterate_julia(vec2 p, vec2 c)
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{
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vec2 z = p;
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float i;
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for (i = 0.; i < N; i++) {
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z = mat2(z, -z.y, z.x) * z + c;
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if (dot(z, z) > B*B) break;
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}
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if (p.y < 0.f) return i;
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return i - log(log(dot(z, z)) / log(B)) / log(2.);
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}
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void main() {
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vec2 R = u_resolution.xy;
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vec2 uv = (u_scale * gl_FragCoord.xy - R - 1.) / R.y - u_translation;
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float n = iterate_julia(uv, u_julia_set) / N;
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vec3 col = pal(fract(n + 0.5), u_rgb_1, u_rgb_2, u_rgb_3, u_rgb_4);
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//if (n == 1.) {n = 0; }
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gl_FragColor = vec4(n == 1. ? vec3(0) : col, 1.);
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}
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