75 lines
2.0 KiB
GLSL
75 lines
2.0 KiB
GLSL
#version 100
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precision highp float;
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uniform float u_time;
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uniform vec2 u_resolution;
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uniform float u_zoom;
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uniform vec2 u_center; // Unused if using perturbation?
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uniform sampler2D u_ref_orbit; // Stores Reference Z (Real=Luminance, Imag=Alpha)
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// Sliders
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uniform float u_exponent; // Perturbation usually assumes Z^2.
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uniform vec2 u_z_start;
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uniform vec2 u_c_offset;
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// Complex Math helpers
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vec2 complex_mul(vec2 a, vec2 b) {
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return vec2(a.x*b.x - a.y*b.y, a.x*b.y + a.y*b.x);
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}
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vec2 complex_sq(vec2 a) {
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return vec2(a.x*a.x - a.y*a.y, 2.0*a.x*a.y);
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}
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void main() {
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// Current pixel coordinate relative to screen center
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vec2 p = (gl_FragCoord.xy - u_resolution.xy * 0.5) / u_resolution.y;
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// Delta C (Difference from Reference Point)
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vec2 dc = p / u_zoom;
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// Apply C Offset from sliders (as Delta C)
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dc += u_c_offset;
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// Initial Delta Z
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vec2 dz = vec2(0.0);
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float iter = 0.0;
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float max_iter = 1000.0;
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for (float i = 0.0; i < 1000.0; i++) {
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// Fetch Reference Z from Texture
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vec4 ref = texture2D(u_ref_orbit, vec2((i + 0.5) / 1024.0, 0.5));
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// Decode Range [0, 1] -> [-4, 4]
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// Z = Val * 8 - 4
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// Use R and G channels (was R and A)
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vec2 Zn = vec2(ref.r * 8.0 - 4.0, ref.g * 8.0 - 4.0);
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// dz = 2*Zn*dz + dz^2 + dc
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vec2 two_Zn_dz = complex_mul(2.0 * Zn, dz);
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vec2 dz_sq = complex_sq(dz);
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dz = two_Zn_dz + dz_sq + dc; // Perturbation formula
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// Check Escape: |Zn + dz|^2 > 4
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vec2 current_z = Zn + dz;
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if (dot(current_z, current_z) > 4.0) {
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iter = i;
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break;
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}
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}
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// Coloring
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float t = iter / max_iter;
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// Standard Black Interior
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if (iter >= 999.0) {
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gl_FragColor = vec4(0.0, 0.0, 0.0, 1.0);
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} else {
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// Original "Generic" Palette
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gl_FragColor = vec4(sqrt(t), t*t, sin(t * 3.14), 1.0);
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}
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}
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