[ODE] Bounciness on Trimesh terrain

[Shamyl Zakariya]

All

I'm writing a game for fun. I have a 4 wheeled vehicle, using a 
simplistic but more or less realistic suspension system and spherical 
wheels, on a trimesh terrain.

Now, the game's been working great -- but in the interest of polish and 
more realistic scale I recently "shrank" the player vehicle as I had 
realized that it was too big to be plausible. Now, the vehicle's about 
2.5 meters long with wheel spheres about 1 meter diameter. ( it was 
huge before... something like 8 meters long )

After shrinking it, the vehicle *bounces* heavily on flat surfaces of 
the terrain. It just sits there and vibrates. As soon as you drive onto 
a hill, or go to any raised surface the bouncing stops and it behaves 
quite well. But, drive back to the flat surface and bouncing starts 
again.

I've tried a few things to minimize or eliminate bounciness.

	-I raised the level of low points in the terrain to be 1m higher than
	 the "ground plane", to eliminate any chances of coplanar conflict

	-I've tuned dContact parameters ( set bounce to zero, twiddled 
soft_cfm and
	 soft_erp ) until my fingers bled.

But I've been unable to quelch it completely.

That said, I could just go back to the full-sized vehicle I was using 
before but I'd like to have more realistic scale in my game.

For reference, I'm using ODE 0.5 on Mac OS X. I'm running ODE at about 
80 Hz, so I don't think it's an issue with too long a timestep, and as 
I said before, when I drive up a hill it becomes rock-solid and stable.

The issue is clearly with terrain triangles with a normal pointing 
straight up.

Any ideas?

Shamyl Zakariya
   "this is, after all, one of those movies where people spend a great
   deal of time looking at things and pointing."
	From a review of _Fantastic Voyage_