From 85cf1849350c5a570d41191b643695b527c906a9 Mon Sep 17 00:00:00 2001
From: Matthias Schiffer <mschiffer@universe-factory.net>
Date: Wed, 3 Feb 2016 15:41:24 +0100
Subject: examples/symmetry: more cleanup

---
 examples/symmetry.frag | 44 ++++++++++++++++++++++++++++++++++----------
 1 file changed, 34 insertions(+), 10 deletions(-)

diff --git a/examples/symmetry.frag b/examples/symmetry.frag
index 90bd71a..26f4651 100644
--- a/examples/symmetry.frag
+++ b/examples/symmetry.frag
@@ -14,31 +14,55 @@ const float sharpness = 300;
 const float PI = 3.14159265358979323846;
 
 
-mat2 rot(float a) {
-	return mat2(
-		cos(a), -sin(a),
-		sin(a), cos(a)
+mat3 rot(float a) {
+	return mat3(
+		cos(a), -sin(a), 0,
+		sin(a), cos(a), 0,
+		0, 0, 1
 	);
 }
 
-float square(vec2 m, float a, float r, vec2 p) {
-	vec2 diff = abs((m - p) * rot(r));
-	float d = max(diff.x, diff.y);
+mat3 scale(float s) {
+	return mat3(
+		s, 0, 0,
+		0, s, 0,
+		0, 0, 1
+	);
+}
 
-	return clamp((a - d)*sharpness, 0.0, 1.0);
+mat3 trans(float x, float y) {
+	return mat3(
+		1, 0, x,
+		0, 1, y,
+		0, 0, 1
+	);
 }
 
+float square(vec3 p) {
+	float d = max(abs(p.x), abs(p.y));
+
+	return clamp((1 - d)*sharpness, 0.0, 1.0);
+}
+
+
 void main(void) {
 	vec2 m = res/2;
 	float s = min(m.x, m.y);
-	vec2 p = (gl_FragCoord.xy - m) / s;
+	vec3 p = vec3((gl_FragCoord.xy - m) / s, 1);
 
 	float scene = 0;
 
 	int n = param0 + 32;
 	float k = param1;
+
 	for (int i = 0; i < n; i++) {
-		float c = square(vec2(0.5, 0) * rot(PI/2*(4.0*i/n)) * vec2(1, 1), 0.3 + 0.02 * param2, -PI/2*(k*i/n + time/1500), p * (1 + 0.03*param2));
+		mat3 t = scale(0.3 + 0.02 * param2)
+		       * rot(-PI/2*(k*i/n + time/1500))
+		       * trans(0.5, 0.0)
+		       * rot(2*PI*i/n)
+		       * scale(1 / (1 + 0.03 * param2));
+
+		float c = square(p * inverse(t));
 		scene = abs(scene - c);
 	}
 
-- 
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