[examples] Fixed shaders_mandelbrot_set for WebGL (#5286)

examples/shaders/resources/shaders/glsl100/mandelbrot_set.fs

@@ -17,6 +17,9 @@ uniform int maxIterations;      // Max iterations per pixel
 const float max = 4.0;          // We consider infinite as 4.0: if a point reaches a distance of 4.0 it will escape to infinity
 const float max2 = max*max;     // Square of max to avoid computing square root
 
+// WebGL shaders for loop iteration limit only const
+const int maxIterationsLimit = 20000;
+
 void main()
 {
     // The pixel coordinates are scaled so they are on the mandelbrot scale
@@ -31,31 +34,29 @@ void main()
     // Fc(z) = z^2 + c on the complex numbers c from the plane does not diverge to infinity starting at z = 0
     // Here: z = a + bi. Iterations: z -> z^2 + c = (a + bi)^2 + (c.x + c.yi) = (a^2 - b^2 + c.x) + (2ab + c.y)i
 
-    int iter = 0;
+    for (int iter = 0; iter < maxIterationsLimit; ++iter)
-    while (iter < maxIterations)
     {
         float aa = a*a;
         float bb = b*b;
-        if (aa + bb > max2)
-            break;
-
-        float twoab = 2.0*a*b;
-        a = aa - bb + c.x;
-        b = twoab + c.y;
-
-        ++iter;
-    }
-
         if (iter >= maxIterations)
         {
             gl_FragColor = vec4(0.0, 0.0, 0.0, 1.0);
+            return;
         }
-    else
+        if (aa + bb > max2)
         {
             float normR = float(iter - (iter/55)*55)/55.0;
             float normG = float(iter - (iter/69)*69)/69.0;
             float normB = float(iter - (iter/40)*40)/40.0;
         
             gl_FragColor = vec4(sin(normR*PI), sin(normG*PI), sin(normB*PI), 1.0);
+            return;
         }
+
+        float twoab = 2.0*a*b;
+        a = aa - bb + c.x;
+        b = twoab + c.y;
+    }
+
+    gl_FragColor = vec4(0.0, 0.0, 0.0, 1.0);
 }

examples/shaders/shaders_mandelbrot_set.c

@@ -70,8 +70,13 @@ int main(void)
     float zoom = startingZoom;
     // Depending on the zoom the mximum number of iterations must be adapted to get more detail as we zzoom in
 	// The solution is not perfect, so a control has been added to increase/decrease the number of iterations with UP/DOWN keys
+#if defined(PLATFORM_DESKTOP)
     int maxIterations = 333;
     float maxIterationsMultiplier = 166.5f;
+#else
+    int maxIterations = 43;
+    float maxIterationsMultiplier = 22.0f;
+#endif
 
     // Get variable (uniform) locations on the shader to connect with the program
     // NOTE: If uniform variable could not be found in the shader, function returns -1