From f9b3a7548177cb2f4bc85f71676b805189206e27 Mon Sep 17 00:00:00 2001
From: polyfloyd <floyd@polyfloyd.net>
Date: Sat, 19 May 2018 16:20:51 +0200
Subject: [PATCH] Add spasm.glsl

---
 spasm.glsl | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 49 insertions(+)
 create mode 100644 spasm.glsl

diff --git a/spasm.glsl b/spasm.glsl
new file mode 100644
index 0000000..d6a7b2d
--- /dev/null
+++ b/spasm.glsl
@@ -0,0 +1,49 @@
+//by @Flexi23, @DanielPettersso, @mrdoob
+
+#ifdef GL_ES
+precision highp float;
+#endif
+#define pi2_inv 0.159154943091895335768883763372
+uniform float time;
+uniform vec2 resolution;
+//uniform vec2 mouse;
+
+// extra changes by @xprogram & @Harley
+
+float border(vec2 uv, float thickness){
+	uv = fract(uv - vec2(0.5));
+	uv = min(uv, vec2(1.)-uv)*2.;
+	return clamp(max(uv.x,uv.y)-1.+thickness,0.,1.)/thickness;
+}
+
+// complex multiplication
+vec2 mul(vec2 a, vec2 b){
+   return vec2( a.x*b.x - a.y*b.y, a.x*b.y + a.y*b.x);
+}
+
+vec2 div(vec2 numerator, vec2 denominator){
+   return vec2( numerator.x*denominator.x + numerator.y*denominator.y,
+                numerator.y*denominator.x - numerator.x*denominator.y)/
+          vec2(denominator.x*denominator.x + denominator.y*denominator.y);
+}
+
+vec2 spiralzoom(vec2 domain, vec2 center, float n, float spiral_factor, float zoom_factor, vec2 pos){
+	vec2 uv = domain - center * 1.0;
+	float d = length(uv);
+	return vec2( atan(uv.y, uv.x)*n*pi2_inv + log(d)*spiral_factor*cos(time), -log(d)*zoom_factor) + pos;
+}
+
+void main( void ) {
+	vec2 uv = gl_FragCoord.xy / max(resolution.x, resolution.y);
+
+	vec2 p1 = vec2(0.25+cos(time*.9)*0.1, 0.3-tan(time*.5)*cos(time));
+	vec2 p2 = vec2(0.75+tan(time)*.1, 0.7-cos(time)*.5);
+
+	vec2 moebius = div(uv-p2, uv-p1);
+
+	vec2 spiral_uv = spiralzoom(moebius,vec2(-0.2),1.,1.6,1.8,-vec2(0.5,0.5)*time*.6);
+	vec2 spiral_uv2 = spiralzoom(moebius,vec2(-0.2),1.,1.6,1.8,-vec2(0.5,0.5)*time*.9);
+	vec2 spiral_uv3 = spiralzoom(moebius,vec2(-0.2),1.,1.6,1.8,-vec2(0.5,0.5)*time*.7);
+	gl_FragColor = vec4(border(spiral_uv,0.3), border(spiral_uv2,0.1) ,border(spiral_uv3,0.9),1.);
+
+}