Add Julia set shader

shaders/julia.frag

@@ -0,0 +1,69 @@
+#version 330 core
+
+out vec4 fragColor;
+
+uniform float u_time;
+uniform uint u_frame;
+uniform vec2 u_resolution;
+uniform vec2 u_mouse;
+
+// Source:
+// https://github.com/kbinani/colormap-shaders/blob/master/shaders/glsl/MATLAB_jet.frag
+float colormap_red(float x) {
+  if (x < 0.7) {
+    return 4.0 * x - 1.5;
+  } else {
+    return -4.0 * x + 4.5;
+  }
+}
+
+float colormap_green(float x) {
+  if (x < 0.5) {
+    return 4.0 * x - 0.5;
+  } else {
+    return -4.0 * x + 3.5;
+  }
+}
+
+float colormap_blue(float x) {
+  if (x < 0.3) {
+    return 4.0 * x + 0.5;
+  } else {
+    return -4.0 * x + 2.5;
+  }
+}
+
+vec4 colormap(float x) {
+  float r = clamp(colormap_red(x), 0.0, 1.0);
+  float g = clamp(colormap_green(x), 0.0, 1.0);
+  float b = clamp(colormap_blue(x), 0.0, 1.0);
+  return vec4(r, g, b, 1.0);
+}
+
+// Julia
+vec2 f(vec2 z, vec2 c) {
+  return vec2(z.x * z.x - z.y * z.y, 2 * z.x * z.y) + c;
+}
+
+float pi = 2.0 * asin(1.0);
+
+void main() {
+  // Changes with time
+  // float a = 2.0 * pi * (int(u_frame) % 500) / 500.0;
+  // vec2 c = 0.7885 * vec2(cos(a), sin(a));
+
+  // Changes with cursor position
+  vec2 c = u_mouse.xy / u_resolution.xy * 2.0 - vec2(1.0, 1.0);
+
+  vec2 z = gl_FragCoord.xy / u_resolution.xy * 3.0 - vec2(1.5, 1.5);
+  int i = 0;
+  while (length(z) <= 2 && i < 1000) {
+    z = f(z, c);
+    i++;
+  }
+  if (i == 1000) {
+    fragColor = vec4(vec3(0.0), 1.0);
+  } else {
+    fragColor = colormap(smoothstep(0.0, 20.0, i));
+  }
+}

shaders/mandelbrot.frag

@@ -48,7 +48,7 @@ vec2 f(vec2 z) {
 void main() {
   vec2 z = vec2(0.0);
   int i = 0;
-  while (length(z) <= 4 && i < 1000) {
+  while (length(z) <= 2 && i < 1000) {
     z = f(z);
     i++;
   }