I'm woking on the GUI subsystem of my engine right now (I'm just making the engine as a educational/fun experience), and I'm trying to figure out the best way to render my GUI efficiently. All of the rendering done for my GUI is either of textured quads or simple colored lines/quads. I've read some things that say that switching vertex streams can be a costly renderr state change (though apparently not so much since DX8), and that mixing multiple vertex formats within a single buffer can be advantageous over having a number of smaller buffers that are swapped in and out. The optimal goal being to try to achieve buffers of around 1000 vertices each. Is it worthwhile to try and figure out to do this in DX9? I use a single dynamic buffer right now for the textured stuff (don't have anything in yet for untextured stuff). I'm thinking te easiest may be to just have two dynamic buffers, one for the textured vertices and one for simple colored vertices. Is this probably the best way to go? One other option I'm considering is to use the single buffer, and just have the untextured stuff have unused values in the texture coordinates and change the color operation to ignore the texture. This would waste space, but I'm thinking it'd be pretty fast (I assume changing color operation state is much faster than switching vertex streams). Anyone have any suggestions? Thanks.

Thanks, that was sort of what I assumed the answer would be. I'll just make sure that my render queue optimizer that I'm working on right now orders by vertex stream towards the top of my shader tree.

By any chance does anyone have a link to an example that makes use of a mixed format vertex stream? I won't implement it for what I'm doing now, but since I'm making this engine purely for enjoyment and educational purposes, I'm curious to see how that is done.