   Point sprite and vertex shader question
  I have a simple particle system of snow flake point sprites falling on a scene which works fine in the fixed function pipeline.  I also have a working untextured (just a single color) particle system for fireworks.  When I made a vertex shader for particles, the untextured particles show, but the textured snow does not.  My book doesn't mention point sprites used with shaders, so I was hoping maybe someone here knew what was up with this.  Passing UVs to the shader doesn't make sense since we're only talking about one vertex...  Perhaps point sprites were never meant to be used with vertex shaders to begin with?   
  You can use point sprites with shaders.  The main thing to be aware of is that you can't output anything to any of the TEXCOORD registers from your vertex shader...these get set "automatically".  The only things you should be outputting are POSITION, PSIZE, COLOR0, and COLOR1 (You can use COLOR0 and COLOR1 to store data you need passed to the pixel shader).  Then in your pixel shader, TEXCOORD0 will automatically get set to appropriate UV coordinates.   ;  Perhaps the problem is that I'm not using a pixel shader yet?  My vertex shader only outputs a position and a color.  We shall see...   