Those of you who are familiar with PhysX plug-in for 3ds Max (for example, recently released 2.40 version) may already notice that by default simulation is not going as smooth as you can expect – rigid body objects are often interpenetrating each other, jittering and jiggling (especially when stacked) , and so on – making it hardly suitable for some scenes.
UPDATE: Not valid for 2.60 PhysX plug-ins and above
So, we’ve contacted Gavin Kistner, Product Designer for PhysX Max and Maya plug-ins at NVIDIA, and he gave us several tips, using those you can deal with simulation stability problems in most of the cases:
TIP I – Increase Frame Rate
If rigid bodies are showing inaccurate behaviour, this is indicating that physics engine is just not performing enough simulation substeps between frames. To fix that (as separate substeps control is yet not availalbe in public versions of PhysX plug-in) you can simply increase Frame Rate before previewing or baking the simulation (and than revert it back to normal during composing, for example).
To illustrate this tip, let’s set up a simple scene – several rigid body planks falling one at each other, trying to form a stack.
With default Frame Rate – 30 fps (shown above), simulation is just messed up. At certain frame planks are stuck together, solver is trying to resolve inter-collisions and repels planks – stack collapses.
But with Frame Rate increased up to 300 fps, simulation is showing much more stable and accurate results.
TIP II – Keep an eye system units.
If your scene consist of small objects (for example, 2cm dice bricks) and you haven’t adjusted Skin Width (which is 1cm by default), you won’t recieve any good outcome as plug-in has been told that your rigid bodies are allowed to penetrate each other by half their width.
Pay attention to unit setup and try to set all parameters accordingly.
Well, that is all for now. If you have something to add, use comments section below.