PhysX: articulated vehicle in PEEL 1.1
This video is a variation on a test scene I previously posted. This is now a configurable test in PEEL 1.1.
The chassis, wheels and axles have relatively large mass ratio differences (40 to 1), which makes things difficult for the iterative solver.
However, as explained in the previous video, using an articulation solves the problem. This is what you see in the beginning of this new video: the vehicle uses an articulation, and everything behaves as expected.
This also shows that articulations can emulate hinge joints just fine, by just setting the joints’ limits properly. There are for example 5 articulated hinges in this simple vehicle.
Now if you disable articulations in the UI and restart the scene, it gets created with regular PhysX joints. And as you can see, the results are not as convincing. Out-of-the-box, it behaves badly (it’s easy to bend the wheels, etc).
But there are still various ways to improve things.
First, you could just use more homogeneous masses. It may not be ‘realistic’ but if it doesn’t actually change the driving experience in the game, it doesn’t really matter. In the video I just set all masses to 1.0 to show that things look more stable & robust that way, i.e. the mass difference is really what breaks this particular setup. It does not have to be 1.0: things become equally stable if you use ‘mass = 40′ for everything.
Now, if you don’t want to change the masses, the usual tricks can be used. Here I just show one of them: create the constraints multiple times. In the video I show what happens if you create them 8 times: while not becoming as robust as articulations, the joints still become visibly more robust.
You could also create them more than 8 times, or increase the solver iteration counts for the vehicle, and so on. Basically there are multiple ways to make such a scene work fine.