fix Mandelbrot divergence threshold; switch to view with correct aspect ratio

shaders/shader.comp

@@ -12,7 +12,7 @@ struct Pixel{
 
 layout(std140, binding = 0) buffer buf
 {
-   Pixel imageData[];
+  Pixel imageData[];
 };
 
 void main() {
@@ -28,29 +28,31 @@ void main() {
   float y = float(gl_GlobalInvocationID.y) / float(HEIGHT);
 
   /*
-  What follows is code for rendering the mandelbrot set. 
+  What follows is code for rendering the mandelbrot set.
   */
   vec2 uv = vec2(x,y);
+  uv.y -= 0.5; // center vertically
+  uv *= vec2(1, 0.75); // adjust for 4:3 aspect ratio
   float n = 0.0;
-  vec2 c = vec2(-.445, 0.0) +  (uv - 0.5)*(2.0+ 1.7*0.2  ), 
+  vec2 c = uv * 3 + vec2(-2.1, 0.0),
   z = vec2(0.0);
-  const int M =128;
+  const int M = 128;
   for (int i = 0; i<M; i++)
   {
     z = vec2(z.x*z.x - z.y*z.y, 2.*z.x*z.y) + c;
-    if (dot(z, z) > 2) break;
+    if (dot(z, z) > 4) break;
     n++;
   }
-          
+
   // we use a simple cosine palette to determine color:
-  // http://iquilezles.org/www/articles/palettes/palettes.htm         
+  // http://iquilezles.org/www/articles/palettes/palettes.htm
   float t = float(n) / float(M);
-  vec3 d = vec3(0.3, 0.3 ,0.5);
-  vec3 e = vec3(-0.2, -0.3 ,-0.5);
+  vec3 d = vec3(0.3, 0.3, 0.5);
+  vec3 e = vec3(-0.2, -0.3, -0.5);
   vec3 f = vec3(2.1, 2.0, 3.0);
   vec3 g = vec3(0.0, 0.1, 0.0);
-  vec4 color = vec4( d + e*cos( 6.28318*(f*t+g) ) ,1.0);
+  vec4 color = vec4( d + e*cos( 6.28318*(f*t+g) ), 1.0);
 
   // store the rendered mandelbrot set into a storage buffer:
   imageData[WIDTH * gl_GlobalInvocationID.y + gl_GlobalInvocationID.x].value = color;
-}
+}