From e269de9f9771ac2620f3f4f892347e592471db23 Mon Sep 17 00:00:00 2001
From: hellerve <veit@veitheller.de>
Date: Tue, 4 Jul 2017 00:57:09 -0400
Subject: [PATCH] weird: added particles

---
 weird/particles.glsl | 62 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 62 insertions(+)
 create mode 100644 weird/particles.glsl

diff --git a/weird/particles.glsl b/weird/particles.glsl
new file mode 100644
index 0000000..c001510
--- /dev/null
+++ b/weird/particles.glsl
@@ -0,0 +1,62 @@
+#ifdef GL_ES
+precision mediump float;
+#endif
+
+#define NP 30
+
+uniform vec2 u_resolution;
+uniform float u_time;
+
+float random (vec2 _st) {
+    return fract(sin(dot(_st.xy, vec2(0.690,0.540)))*43758.817);
+}
+
+float random(float i) {
+    return fract(sin(i)*1e5);
+}
+
+float noise (vec2 _st) {
+    vec2 i = floor(_st);
+    vec2 f = fract(_st);
+
+    float a = random(i);
+    float b = random(i + vec2(1.0, 0.0));
+    float c = random(i + vec2(0.0, 1.0));
+    float d = random(i + vec2(1.0, 1.0));
+
+    vec2 u = f * f * (3.0 - 2.0 * f);
+
+    return mix(a, b, u.x) +
+            (c - a)* u.y * (1.0 - u.x) +
+            (d - b) * u.x * u.y;
+}
+
+struct particle {
+  vec2 vel;
+  vec2 pos;
+};
+
+void update_particle(inout particle p) {
+    p.pos += p.vel;
+}
+
+vec3 show_particle(particle p, vec3 c) {
+	vec2 st = gl_FragCoord.xy/u_resolution.xy;
+    particle o = p;
+    update_particle(p);
+    return abs(st.x-p.pos.x)+abs(st.y-p.pos.y)<0.1?c:vec3(0.);
+}
+
+void main() {
+    vec2 st = gl_FragCoord.xy/u_resolution.xy;
+    vec3 color = vec3(0.);
+    
+    for (int i = 1; i < NP; i++) {
+      vec2 pos = vec2(0.);
+      vec2 vel = vec2(noise(st*float(i)*u_time*0.3), noise(st*float(i)));
+      particle p = particle(vel, pos);
+      color += show_particle(p, vec3(.3));
+    }
+    
+    gl_FragColor = vec4(color, 1.);
+}