can anyone explain rhw?
can anyone give me an idea of what exactly the rhw co-ordinate you can specify for FVF's does? looking at the sdk example, i have the idea it could be used to project geometry flat to the screen (to make for example a 'window'). if that is the case how does the z cartesian effect things when rhw is used?
The RHW flag basically says that you do not want Direct3D to transform and light your vertices. They are taken to already be transformed and lit. As you stated you might want to do this for a 2D overlay for example.
...or for using D3D to display something like a tile map with lighting or something. You can use the rhw coeffecients to implement your own lighting equations. Very handy.