Author Topic:   Terrain reflections
posted December 10, 1999 10:37 AM            
Now that everyone here is working on rendering terrain fast, has anyone thoughts on how to render reflected terrain in ROAM-based terrain engine?

Reflective water might be easy to draw because water surface is rarely oblique unless you want very big waves. And reflective water is mainly what I'm looking for.



LDA Seumas
posted December 22, 1999 03:04 AM           
I think this is a tricky subject...

I've been trying to come up with ways to render reflected terrain without using a stencil buffer, and I haven't been able to figure out anything that would actually work. A user clip plane (as Q3A uses) would be helpful, and z-buffer tricks can be used to an extent...

Hmm, perhaps if the water's surface was made into a user clip plane for _both_ the rendering of the reflection and the rendering of the terrain. Then the edges should meet perfectly at the water's edge, and a semi-transparent water surface could still be rendered over. You would lose the visibility of the lake/river's bottom, but would gain terrain reflections... Right now in TM you can see the bottom of the water area, and the surface reflection is just the environment mapped sky. Using a user clip-plane while OpenGL rendering all terrain geometry might be slow on some (if not all) consumer hardware though.

-- Seumas McNally, Lead Programmer, Longbow Digital Arts