1 files changed, 49 insertions, 0 deletions
diff --git a/assets/shader/snow.fs b/assets/shader/snow.fs
new file mode 100644
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--- /dev/null
+++ b/assets/shader/snow.fs
@@ -0,0 +1,49 @@
+// Copyright (c) 2013 Andrew Baldwin (twitter: baldand, www: http://thndl.com)
+// License = Attribution-NonCommercial-ShareAlike (http://creativecommons.org/licenses/by-nc-sa/3.0/deed.en_US)
+
+// "Just snow"
+// Simple (but not cheap) snow made from multiple parallax layers with randomly positioned
+// flakes and directions. Also includes a DoF effect. Pan around with mouse.
+
+#define LIGHT_SNOW // Comment this out for a blizzard
+
+#ifdef LIGHT_SNOW
+	#define LAYERS 50
+	#define DEPTH .5
+	#define WIDTH .3
+	#define SPEED .6
+#else // BLIZZARD
+	#define LAYERS 200
+	#define DEPTH .1
+	#define WIDTH .8
+	#define SPEED 1.5
+#endif
+
+precision mediump float;
+
+uniform float iTime;
+uniform vec2 iResolution;
+uniform vec2 iMouse;
+
+void main()
+{
+	const mat3 p = mat3(13.323122,23.5112,21.71123,21.1212,28.7312,11.9312,21.8112,14.7212,61.3934);
+	vec2 uv = iMouse.xy/iResolution.xy + vec2(1.,iResolution.y/iResolution.x)*gl_FragCoord.xy / iResolution.xy;
+	vec3 acc = vec3(0.0);
+	float dof = 5.*sin(iTime*.1);
+	for (int i=0;i<LAYERS;i++) {
+		float fi = float(i);
+		vec2 q = uv*(1.+fi*DEPTH);
+		q += vec2(q.y*(WIDTH*mod(fi*7.238917,1.)-WIDTH*.5),SPEED*iTime/(1.+fi*DEPTH*.03));
+		vec3 n = vec3(floor(q),31.189+fi);
+		vec3 m = floor(n)*.00001 + fract(n);
+		vec3 mp = (31415.9+m)/fract(p*m);
+		vec3 r = fract(mp);
+		vec2 s = abs(mod(q,1.)-.5+.9*r.xy-.45);
+		s += .01*abs(2.*fract(10.*q.yx)-1.);
+		float d = .6*max(s.x-s.y,s.x+s.y)+max(s.x,s.y)-.01;
+		float edge = .005+.05*min(.5*abs(fi-5.-dof),1.);
+		acc += vec3(smoothstep(edge,-edge,d)*(r.x/(1.+.02*fi*DEPTH)));
+	}
+	gl_FragColor = vec4(vec3(acc),1.0);
+}