nicer particles, adding code so that particles don't penetrate through planets. added not-yet compeleted intersection code.

data/shader/particle.frag

@@ -1,10 +1,13 @@
 #version 120
+varying vec3  position;
 varying vec2  vertex;
 varying vec3  velocity;
 varying float decay;
 
 varying float explCenterDist;
 
+float pi = 3.14159;
+
 vec3 hsv2rgb(vec3 c)
 {
     vec4 K = vec4(1.0, 2.0 / 3.0, 1.0 / 3.0, 3.0);
@@ -12,15 +15,28 @@ vec3 hsv2rgb(vec3 c)
     return c.z * mix(K.xxx, clamp(p - K.xxx, 0.0, 1.0), c.y);
 }
 
+float hash(float n)
+{
+    return fract(sin(n)*43758.5453);
+}
+
 void main()
 {
-    float r = length(vertex);
-    if (r > 1.0) {
+    // normalize radius from 0..1
+    vec2 vn = 2.0*vertex;
+    float rn = length(vn);
+    float angle = atan(vn.y, vn.x);
+    float hs = 20.0;
+    float removeCorners = 0.5 * (hash(fract(hs*vertex.x)) + hash(fract(hs*vertex.y)));
+    if (rn+removeCorners > 1.0) {
         discard;
     }
 
+    //float rf = 0.5-0.5*rn;
+    float rf = 1.0;
+
     float d = decay/(1.0+max(0.0, 1.0-2.0*explCenterDist));
-    float h = (1.0-d)/6.0;
+    float h = max(0.0, (1.0-d)/6.0) * rf;
     float v = max(0.0, (1.0-log(d)));
     float s = max(0.0, min(30.0 * sqrt(decay) * explCenterDist, 1.0));
 
@@ -30,4 +46,5 @@ void main()
     gl_FragColor = vec4(hsv2rgb(vec3(h, s, v)), 1.0);
 
     //gl_FragColor = vec4(1.0, 1.0, 0.0, 1.0);
+    //gl_FragColor.rgb = vec3(0.5+0.5*(a/pi));
 }

data/shader/particle.vert

@@ -14,6 +14,7 @@ varying float decay;
 varying vec3  velocity;
 varying vec2  vertex;
 varying float explCenterDist;
+varying vec3  position;
 
 uniform float aspectRatio;
 
@@ -31,9 +32,9 @@ void main()
   // faster particles are smaller
   // TODO: scale by time too! scale down fast after 3 halfAges
   float scaleBySpeed = (1.0 - 0.95*length(in_velocity)/maxVelocity);
-  float finalSize = size * scaleBySpeed;
+  float finalSize = size * scaleBySpeed * (1.0-max(0.0, decay-3.0*halfAge)/2.0);
   vec2 base = in_geometry;
-  vec3 p = finalSize*vec3(base, 0.0);
+  vec3 p = vec3(finalSize*base, 0.0);
   vec3 move = (0.2*age + log(1.0+age*5.0)) * in_velocity;
   float md = length(move);
   if (md > in_maxDist) {
@@ -46,6 +47,7 @@ void main()
 
   vertex   = base.xy;
   velocity = in_velocity;
+  position = in_position;
 
   explCenterDist = length(explCenter - offset);
 }