1 files changed, 32 insertions, 0 deletions
diff --git a/sketches/04/polka.frag b/sketches/04/polka.frag
new file mode 100644
index 0000000..97baa9c
--- /dev/null
+++ b/sketches/04/polka.frag
@@ -0,0 +1,32 @@
+varying vec4 v_position;
+uniform vec2 u_resolution;
+uniform float u_time;
+
+#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 - 1.0)/vec2(1.0, ratio);
+
+  vec2 cell_pos = abs(floor(pos / segment)) - 0.5;
+  int alt = int(mod(cell_pos.x + cell_pos.y, 2.));
+
+  float radius = (sin(time - length(pos + 0.5)) + 1.)*0.02;
+  if (alt == 0) {
+    radius = (0.04 - radius);
+  }
+
+  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.);
+    }
+  }
+}
+