moved a few Extras projects into Extras/obsolete.

Extras/obsolete/GPUphysics/collisionShader.frag

@@ -0,0 +1,30 @@
+
+uniform sampler2D position       ;
+uniform sampler2D old_collisions ;
+
+void main()
+{
+  vec2   my_id = gl_TexCoord[0].st ;
+  vec2   pr_id = gl_TexCoord[1].st ;
+
+  /* Object colliding with itself */
+
+  if ( length ( my_id - pr_id ) < 0.05) discard ;
+
+  vec2 last_id = texture2D ( old_collisions, my_id ).xy ;
+
+  /* Object collision that will already have been dealt with */
+
+  if ( pr_id.y >= last_id.y ) discard ;
+  if ( pr_id.y == last_id.y && pr_id.x >= last_id.y) discard ;
+
+  vec3  my_pos = texture2D ( position, my_id ).xyz ;
+  vec3  pr_pos = texture2D ( position, pr_id ).xyz ;
+
+  /* Objects that don't actually collide */
+
+  if ( length ( my_pos - pr_pos ) >= 2.0 ) discard ;
+
+  gl_FragColor = vec4 ( pr_id, 0, 1 ) ;
+}
+