Problems with collision checking

[joevenzon]

You know, it's funny, I was just thinking that this could happen the other day, but hadn't tried it. There are two problems:
1) if the car is moving down really fast, it's possible for the wheel to get through the ground before the collision detection sees it, and then one or more wheels are just stuck there
2) if the car has a lot of downward momentum, and it causes the suspension to run out of travel, the suspension bottoms out but provides no further force and the car sinks into the ground momentarily

For 1 the way to fix this would be to make sure to check for collisions along the line formed by the current wheel patch contact position minus the previous wheel patch contact position, and force it to stop at any barriers.

For 2 there are a couple of options:
a) make all suspensions have (effectively) infinite travel regardless of what is in the .car specification -- would cause the car to very briefly go slightly under the ground and then bounce up some
b) make a "bumper" so when the spring bottoms out a much higher K spring kicks in -- a good option but can cause the car to really bounce high in the air after a big landing
c) if the suspension bottoms out, enforce staying on the ground by just moving the car up as needed -- this seems like a good option, I can't see any real problems with it but I haven't thought it through very far