cool cool cool

learning/2d_matrices/scale.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)); }
+
+vec2 rotate(vec2 st, float a) {
+  st = mat2(cos(a),-sin(a),sin(a),cos(a))*(st);
+  return st;
+}
+
+vec2 scale(vec2 st, vec2 scale) {
+  return mat2(scale.x,.0,.0,scale.y)*st;
+}
+
+float fill(float x, float size) { return 1.-step(size, x); }
+
+float crossSDF(vec2 st, float s) {
+  vec2 size = vec2(.25, s);
+  float a = max(abs(st.x/size.x),abs(st.y/size.y));
+  float b = max(abs(st.x/size.y),abs(st.y/size.x));
+  return min(a,b);
+}
+
+
+void main() {
+  vec2 st = gl_FragCoord.xy/u_resolution;
+  st.x *= u_resolution.x/u_resolution.y;
+  st = (st-.5)*2.;
+  vec3 color = vec3(0.0,0.0,0.0);
+  float alpha = 1.0;
+  st += vec2(sin(u_time),cos(u_time))*.35;
+  st = scale(st, vec2(sin(u_time),sin(u_time)));
+  st = rotate(st,sin(u_time));
+  float c = crossSDF(st,1.);
+  
+  color = vec3(st.x,st.y,.0);
+  color += fill(c,.2);
+  
+
+  gl_FragColor = vec4(color, alpha);
+}