Distortion/Heat haze and foreground

[sqrt[-1]]

Hi,

I was wondering what the current techniques are for rendering distortion/heat haze type effects and how it interacts with foreground geometry.

Basically the artefacts I am currently seeing in my first pass implementation is foreground objects bleeding into the distortion.

Render pass is:
- Render all scene geometry
- Get color buffer as texture
- Render distortion objects into the scene (either access texture directly or defer to post process)

Now I could have multiple resolves of the scene color to a texture based on where distortion geometry is in the scene - and sort scene and render back to front (which breaks my depth only pass as well) - but is there some trick I can use (perhaps using the depth buffer?) to exclude foreground geometry bleeding?

I have also noticed this artefact in some games (quake wars water).

 

[zhugel_007]

Crysis is using this:
http://http.developer.nvidia.com/GPUGems2/gpugems2_chapter19.html
There will be some artifacts on the edge part, but it is not really noticeable if you control the offset well while sampling the back buffer texture. I didn't notice this while playing crysis until I know the trick they were using. (Check the sea water of the game.)

 

[sqrt[-1]]

Thanks, that is exactly what I was looking for.