In the original SDK, we included a custom
version of q3map which supported different surface paramaters that would
in turn effect the physics of the car. This is no longer needed as these
kind of features are now included in the standard gtkradiant q3map.
There will be a file "scripts/custinfoparms.txt"
included with the new mappers pack that allows the use of the Q3R
surface params. The commandline option when compiling a bsp to use these
new custom surface params is like this...
q3map -custinfoparms <mapname>
When writing the shaders for any textures you can use "grass", "asphalt" and "wet" as surfaceparams. You can also combine them to get different combination. For example having surfaceparm asphalt and surfaceparm wet on the same texture will cause it to be wet asphalt. Wet can also work with grass and dust, but
we would have to code the effects of the combinations into the mod before you can see the result of the two on the car physics. Also if you need to make ice use the "slick" surfaceparm.