Physical Prims - need a quick rundown

Hi all,

I was asked last night at a noob show-and-tell if there was any information on working with physical prims.

I avoid physical prims like the plague, so I directed them to ask a few other people that volunteered their time.

But, he got me wondering...what are the rules and guidelines for working with physical prims? Does it really have to do more with scripting than with building? Can anyone contribute to a "Do this/don't do this" type of list of things people should know when starting to work with physical prims?

Any information people can volunteer, I'd like to put in a notecard and distribute at the New Citizens Inc. center (and anyone else that wants one).

Thanks in advance!

Never use physics or joints unless you know exactly what you are doing.
It totally kills the server, and there isn't much use for them.
Physics is more for vehicles than houses

Fair 'nuff - that's about all I personally know about them, which is enough to keep me faaaaaaaaar away from that particular checkbox.


I guess what I'm looking for is advice for the new builder - ok, vehicle builder - that wants to enable physics but doesn't want to crash a sim doing it. I know there is a mass variable involved, right? No? Eeep!

The more comlex the shape, the more work the physics engine has to do to deal with it. It's not to hard to create a shape that will bring a sim to its knees, or slip outside the physical constraints that Havok is supposed to be enforcing. The two basic rules I know of are:

- Curved surfaces are hard.
- Concave surfaces are hard.

I'm sure there are other rules, but that's all I've managed to figure out.

As a newbie builder I created a simple physics bomb by putting a few spheres into a hollowed torus. The darn thing blew up and I found the pieces scattered over half a sim.

A linked chain of tori can crash a sim. Really easily.

A simple hamster ball is deceptively hard to do. If you make the sphere too small, you can run out of it by moving faster than Havok can keep up with. You have to make the sphere pretty large to stay inside as you move around.

I don't think there is any way to affect the mass of a physical object other than hollowing its prims. However, changing the material type can change its bounciness - rubber objects bounce higher than stone ones.

i thinkt he llsetbuoyancy can help to manage a bit the mass