Rendering to a Texture

Maintaining the correct viewport and projection/model matrices proved to be the most difficult task in rendering particles to a texture.  The viewport must be set to the same size as the texture attached to the framebuffer when rendering to a texture and this causes variations in the perspective from the default window framebuffer.  The velocity grid must be aligned such that it intersects the (texture framebuffer's) viewing frustrum perfectly.  Unfortunately, an orthogonal projection will not work in this case since z values are needed for the depth render buffer attached to the texture framebuffer.

I managed to get the particles rendering to a texture (still animating in real-time) and apply them to a simple cube:

Next I will focus on rendering and animating this texture in the terrain scene and continuing to modify colour values for the output textures.  Also, currently only one texture is rendered at the end of the velocity computation, but ideally multiple textures will be rendered and combined later on.