setting up shader experiments

shader_experiments/hard-shader.frag

@@ -0,0 +1,70 @@
+// copied from http://glslsandbox.com/e#47841.0
+
+#ifdef GL_ES
+precision mediump float;
+#endif
+
+uniform float u_time;
+uniform vec2 u_mouse;
+uniform vec2 u_resolution;
+uniform float u_tick;
+
+float map(vec3 p)
+{
+    const int MAX_ITER = 20;
+    const float BAILOUT=2.0;
+    float Power =2.;
+
+    vec3 v = p;
+    vec3 c = vec3(cos(u_time*0.1), cos(u_time * 0.05234567), v.z);
+
+    float r=0.0;
+    float d=1.0;
+    for(int n=0; n<MAX_ITER; n++)
+    {
+        r = length(v);
+        float zr = pow(r,Power);
+        if(zr/r>BAILOUT) break; // improved
+
+        float theta = atan(v.z/length(v.xy)*tan(u_mouse.x*1.57))*tan(u_mouse.y*2.);
+        float phi = atan(v.y, v.x);
+        d = pow(r,Power-1.0)*Power*d+1.;
+
+        //theta = theta*2.;
+        phi = phi*Power;
+        v = (vec3(cos(theta)*cos(phi), sin(phi)*cos(theta), sin(theta))*zr)+c;
+    }
+    return 0.5*log(r)*r/d;
+}
+
+
+void main( void )
+{
+    vec2 pos = (gl_FragCoord.xy*2.0 - u_resolution.xy) / u_resolution.y;
+    vec3 camPos = vec3(1, 1, 1.5);
+    vec3 camTarget = vec3(0.0, 0.0, 0.0);
+
+    vec3 camDir = normalize(camTarget-camPos);
+    vec3 camUp  = normalize(vec3(0.0, 1.0, 0.0));
+    vec3 camSide = cross(camDir, camUp);
+    float focus = 1.8;
+
+    vec3 rayDir = normalize(camSide*pos.x + camUp*pos.y + camDir*focus);
+    vec3 ray = camPos;
+    float m = 0.0;
+    float d = 0.0, total_d = 0.0;
+    const int MAX_MARCH = 150;
+    const float MAX_DISTANCE = 10.0;
+    for(int i=0; i<MAX_MARCH; ++i) {
+        d = map(ray);
+        total_d += d*1.11;
+        ray += rayDir * d;
+        m += 1.0;
+        if(d<0.0002) { break; }
+        if(total_d>MAX_DISTANCE) { total_d=MAX_DISTANCE; break; }
+    }
+
+    float c = (total_d)*0.0001;
+    vec3 result = vec3( vec3(0.8, 0.23, 0.1)*m*0.02 );
+    gl_FragColor = vec4(result, 1);
+}