   Particle Effects - Point Sprites or Quads?
  I am working on a 2D strategy game using MDX.I have added some 3D particle effects using point sprites. I have a few issues. I would like to rotate the particles. Can I rotate point sprites?I would like to adjust the alpha on each particle individually. Right now I am adjusting the alpha of the texture, but the point sprites all fade at the same time because they all use the same texture.How can I adjust the alpha of a point sprite without using a specific alpha color in my image? I would like to continue to use the alpha channel of my png graphic files.How do I do fog and smoke effects? Are those just big point sprites with a lot of alpha?Should I be using point sprites at all? I have used a quad for my user interface. Would rendering a bunch of quads have any negative side effects?   
  You can store a colour in the vertex buffer (the diffuse component, for example), and pass it through to the pixel shader. You can then do what you want with it, like use its alpha or modulate its colour and alpha.I think that point sprites are best for a bunch of similar looking sprites that just differ in colour (like the above) and size, but I don't have that much experience with them. I think that if you have a lot of different textures, quads can be a more natural way to access them from a texture atlas.   ;  You cannot rotate Point Sprites, sadly. In order to rotate particles, it's up to quads.   ;  I would say that you should be safe going with sprites rather than quads. Quads are a bit more flexible in the stuff you are trying to accomplish.   ;  Not being able to rotate point sprites can be a huge limitation, especially when creating pyro effects like explosions and smoke. For some inspiration, you might want to check out the quad based particle system of this shabby MDX game (it's in ParticleEngine.cs I believe, I have yet to write the article). It's not the most robust, elegant or even efficient particle system, but it should give you some ideas for the rotation and alpha stuff.Hope this helps :)   