very nice particles with heat in the center of the explosion and moving in 3d space.

data/shader/particle.frag

@@ -1,8 +1,11 @@
 #version 120
-varying vec2 vertex;
-varying vec2 velocity;
+varying vec2  vertex;
+varying vec3  velocity;
 varying float decay;
 
+varying float explCenterDist;
+uniform vec3  explCenter;
+
 vec3 hsv2rgb(vec3 c)
 {
     vec4 K = vec4(1.0, 2.0 / 3.0, 1.0 / 3.0, 3.0);
@@ -17,10 +20,16 @@ void main()
     if (r > 1.0) {
         discard;
     }
-    float d = decay;
+
+    float d = decay/(1.0+max(0.0, 1.0-explCenterDist));
     float h = (1.0-d)/6.0;
-    float v = max(0.0, (1.0-d/2.0) - 0.1*(d*d*d));
+    float v = max(0.0, (1.0-log(d)));
     float s = 1.0;
+
+    //v /= decay * 10.0*length(vertex-explCenter);
+    //v /= 1.0+2.0*length(vertex-explCenter);
+    v /= 1.0 + max(0.0, min(35.0*(decay-0.2), 1.0)) * 15.0 * explCenterDist;
+
     gl_FragColor = vec4(hsv2rgb(vec3(h, s, v)), 1.0);
 
     //gl_FragColor = vec4(1.0, 1.0, 0.0, 1.0);

data/shader/particle.vert

@@ -1,26 +1,37 @@
 #version 120
 attribute vec2 in_vertex;
-attribute vec2 in_position;
-attribute vec2 in_velocity;
+attribute vec3 in_position;
+attribute vec3 in_velocity;
 
-uniform float maxAge;
-varying float decay;
-varying vec2 velocity;
-varying vec2 vertex;
-uniform float time;
+uniform float age;
 uniform float size;
+uniform float maxVelocity;
+uniform float maxAge;
+uniform vec3  explCenter;
+
+varying float decay;
+varying vec3  velocity;
+varying vec2  vertex;
+varying float explCenterDist;
+
+// TODO: rotate to face the user!
 void main()
 {
-  //decay = min(1.0, time+5.0*length(velocity)) / maxAge;
+  //decay = min(1.0, age+5.0*length(velocity)) / maxAge;
   //decay = max(decay*decay, sqrt(decay));
-  decay = time / maxAge;
+  decay = age / maxAge;
 
+  // faster particles are smaller
+  float s = size * (1.0-length(in_velocity)/maxVelocity);
   vec2 base = in_vertex;
-  vec2 p = size*base;
-  p += log(1.0+time) * in_velocity;
-  p += in_position;
-  gl_Position = vec4(p, 0.0, 1.0);
+  vec3 p = s*vec3(base, 0.0);
+  vec3 offset = log(1.0+age) * in_velocity + in_position;
+  p += offset;
 
-  vertex   = base;
+  gl_Position = vec4(p, 1.0);
+
+  vertex   = base.xy;
   velocity = in_velocity;
+
+  explCenterDist = length(explCenter-offset);
 }