feat: optimizes and changes polka a bit

1 files changed, 15 insertions, 20 deletions

diff --git a/sketches/04/polka.frag b/sketches/04/polka.frag
index 1a93292..97baa9c 100644
--- a/sketches/04/polka.frag
+++ b/sketches/04/polka.frag
@@ -2,35 +2,30 @@ varying vec4 v_position;
 uniform vec2 u_resolution;
 uniform float u_time;
 
-#define MAX_ITERATIONS 100
 #define DOTS 32.
 
+const float segment = 2.0 / (DOTS + 1.);
+
 void main() {
   float time = u_time * 2.;
 
   float ratio = u_resolution.x / u_resolution.y;
-  vec2 pos = v_position.xy/vec2(1.0, ratio);
-
-  gl_FragColor = vec4(0., 0., 0., 1.);
+  vec2 pos = (v_position.xy - 1.0)/vec2(1.0, ratio);
 
-  float segment = 2.0 / (DOTS + 1.);
+  vec2 cell_pos = abs(floor(pos / segment)) - 0.5;
+  int alt = int(mod(cell_pos.x + cell_pos.y, 2.));
 
-  for (float i = 0.; i < DOTS; i++) {
-    for (float j = 0.; j < DOTS; j++) {
-      int alt = int(mod(i + j, 2.));
-      vec2 step = vec2(segment * (i + 1.0), segment * (j + 1.0));
-      float radius = (sin(time - length(pos)) + 1.)*0.02;
-      if (alt == 0) {
-        radius = (0.04 - radius);
-      }
+  float radius = (sin(time - length(pos + 0.5)) + 1.)*0.02;
+  if (alt == 0) {
+    radius = (0.04 - radius);
+  }
 
-      if (length(pos - 1. + step) < radius) {
-        if (alt == 0) {
-          gl_FragColor = vec4(.17, .24, .31, 1.);
-        } else {
-          gl_FragColor = vec4(0.75, 0.22, 0.17, 1.);
-        }
-      }
+  gl_FragColor = vec4(0., 0., 0., 1.);
+  if (length(pos - 0.0 + cell_pos*segment) < radius) {
+    if (alt == 0) {
+      gl_FragColor = vec4(.17, .24, .31, 1.);
+    } else {
+      gl_FragColor = vec4(0.75, 0.22, 0.17, 1.);
     }
   }
 }