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experiments/exercises/offset_patterns.frag

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+#ifdef GL_ES
+precision mediump float;
+#endif
+uniform vec2 u_resolution;
+uniform vec2 u_mouse;
+uniform float u_time;
+
+#define PI 3.14159265359
+
+const vec3 uAColor = vec3(.5,.5,.5);
+const vec3 uBColor = vec3(.5,.5,.5);
+const vec3 uCColor = vec3(1.,1.,1.);
+const vec3 uDColor = vec3(.0,.33,.67);
+
+//get colors from http://dev.thi.ng/gradients/
+vec3 cosPalette(float t) { return uAColor + uBColor*cos(6.28318*(uCColor*t+uDColor)); }
+
+float fill(float x, float size) { return 1.-step(size, x); }
+
+float circleSDF(vec2 st) { return length(st); }
+
+void main() {
+  vec2 st = (gl_FragCoord.xy*2. - u_resolution.xy)/u_resolution.y;
+  vec3 color = vec3(0.0,0.0,0.0);
+  float alpha = 1.0;
+  float sp = u_time/2.;
+  float m = step(mod(sp*10.,2.),1.);
+  vec2 st2 = st;
+  //vec2 st2 = fract(st*10.)-.5;
+  //vec2 u = step(mod(vec2(2.),fract(st2)*10.),vec2(1.))*2.-1.;
+  //u = vec2(1.);
+  st2.x += u.x*fract(sp*m);
+  st2.y += u.y*fract(sp*(1.-m));
+  st2 = fract(st2*10.)-.5;
+  st2 *= 2.;
+  float circle = (circleSDF(st2));
+  float circle2 = (circle);
+  color += fill(circle,.2);
+  color += fill(min(circle,circle2),.5);
+
+  gl_FragColor = vec4(color, alpha);
+}