From 5d6b59778a7346317ddfc549c350c0960a7a54a7 Mon Sep 17 00:00:00 2001
From: Charles <sircharlesaze@gmail.com>
Date: Wed, 20 May 2020 12:42:39 +0200
Subject: Added Smoothness and super sampling

---
 shader/fragment.glsl | 115 +++++++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 98 insertions(+), 17 deletions(-)

(limited to 'shader')

diff --git a/shader/fragment.glsl b/shader/fragment.glsl
index 6720236..6bc028c 100644
--- a/shader/fragment.glsl
+++ b/shader/fragment.glsl
@@ -11,36 +11,117 @@ uniform float       u_imag_start;
 uniform float       u_imag_end;
 
 uniform int         u_iterations;
+uniform bool        u_smooth;
+uniform float       u_samples;
 
 uniform sampler1D   u_texture;
 
 #define ESCAPE_RADIUS 4.0
+#define LOG_2 0.69314718056
 
-void main()
-{
-    float   ca = u_real_start + float(gl_FragCoord.x) / float(u_width) * (u_real_end - u_real_start);
-    float   cb = u_imag_start + float(gl_FragCoord.y) / float(u_height) * (u_imag_end - u_imag_start);
-    float	zr = ca;
-    float	zi = cb;
 
-    float	zr_square;
-    float	zi_square;
+int     mandelbrot_func(vec2 c)
+{
+    vec2    z;
+    vec2    z_square;
     int     n;
 
+    z = c;
     for (n = 0; n < u_iterations; n++)
     {
-        zi_square = zi * zi;
-        zr_square = zr * zr;
-        if (zr_square + zi_square > ESCAPE_RADIUS)
+        z_square = z * z;
+        if (z_square.x + z_square.y > ESCAPE_RADIUS)
             break;
-        zi = 2.0 * zr * zi;
-        zr = zr_square - zi_square;
-        zi += cb;
-        zr += ca;
+        z.y = 2.0 * z.x * z.y;
+        z.x = z_square.x - z_square.y;
+        z += c;
     }
+    return n;
+}
 
+float   mandelbrot_smooth(vec2 c)
+{
+    vec2    z;
+    vec2    z_square;
+    int     n;
+
+    z = c;
+    for (n = 0; n < u_iterations; n++)
+    {
+        z_square = z * z;
+        if (z_square.x + z_square.y > ESCAPE_RADIUS)
+            break;
+        z.y = 2.0 * z.x * z.y;
+        z.x = z_square.x - z_square.y;
+        z += c;
+    }
     if (n == u_iterations)
-        out_color = vec4(0.0, 0.0, 0.0, 1.0);
+        return float(n);
+    // http://linas.org/art-gallery/escape/escape.html
+    z_square = z * z;
+    z.y = 2.0 * z.x * z.y;
+    z.x = z_square.x - z_square.y;
+    z += c;
+    z_square = z * z;
+    z.y = 2.0 * z.x * z.y;
+    z.x = z_square.x - z_square.y;
+    z += c;
+    float modulus = sqrt(z.x * z.x + z.y * z.y);
+    return float(n) - log(log(modulus)) / LOG_2;
+}
+
+vec4   mandelbrot_color(vec2 c)
+{
+    float   n;
+
+    if (u_smooth)
+        n = mandelbrot_smooth(c);
+    else
+        n = float(mandelbrot_func(c));
+
+    if (n == float(u_iterations))
+        return vec4(0.0, 0.0, 0.0, 1.0);
+    else
+        return texture(u_texture, n / float(u_iterations));
+
+}
+
+vec4    supersample_grid(vec2 c)
+{
+    vec2    epsilon;
+    vec2    _sample;
+    vec2    _step;
+    vec4    color;
+
+    color = vec4(0.0, 0.0, 0.0, 0.0);
+    _step.x = (u_real_end - u_real_start) / float(u_width);
+    _step.y = (u_imag_end - u_imag_start) / float(u_height);
+    epsilon.y = 0.0;
+    while (epsilon.y < u_samples)
+    {
+        epsilon.x = 0.0;
+        while (epsilon.x < u_samples)
+        {
+            _sample = c + _step * (epsilon / u_samples);
+            color += mandelbrot_color(_sample);
+            epsilon.x += 1.0;
+        }
+        epsilon.y += 1.0;
+    }
+    return color / (u_samples * u_samples);
+}
+
+void main()
+{
+    vec2    c;
+    float   n;
+
+    c.x = u_real_start + float(gl_FragCoord.x) / float(u_width) * (u_real_end - u_real_start);
+    c.y = u_imag_start + float(gl_FragCoord.y) / float(u_height) * (u_imag_end - u_imag_start);
+
+
+    if (u_samples == 1.0)
+        out_color = mandelbrot_color(c);
     else
-        out_color = texture1D(u_texture, float(n) / float(u_iterations));
+        out_color = supersample_grid(c);
 }
-- 
cgit