Library of physics materials?

[Colin]

Hi,


I am striving for realism in my games/sims, and was wondering if there was a freely-available list of various real-world materials' properties suitable for use with Newton? I was looking for something like coefficients of restitution, mass over volume, softness, static and dynamic friction (both wet and dry.)

Do you have something like that, Julio?

If you (or anyone) has such a list, it would be really really awesome to the community if you could make it available. Thanks!


Colin

[Julio Jerez]

there are tables on the internet for friction, like this one
http://www.engineeringtoolbox.com/frict ... d_778.html

I have never found a table for restitution.
Restitution is a very empirical values, and when it comes to a rigid body simulation it even more inaccurate. Rigid body is a very stringent condition.
In fact the coefficient is only correct when applied to tow bodies in insulation. when three or more bodies collide the assumption of a Eleatic coefficient of restitution is incorrect.

In Newton of example if you use continues collision the engine do diffrentecie between impulsive force and Resting forces, and solve the according to the existing Laws of conservation of momentum
when no using continues collision, Impulse is converted to a force over the time step, and the solution the this are use as forces, so the resulting an approximation.

in most case this is accurate enough, by there are case where fore example a Poll Game or a Newton Cradle when tat assumption will fail. The engine will resolve those problems correctly when in CCD mode. In all cases the assumption of rigid body is an idealization that will intrude error.

The Softness, is just a bogus values that is use for resolving interpolation. In the set to a very small value, and I would no change that.
Basically this values say when tow bodies are interpenetration be calculation the minimal penetration distance and convert that into a constant velocity the will separate the bodies.
Softness is the coefficient that convert penetration to velocity.
AS you can see this value have to physical meaning and add energy to the system. so it is important that the coefficient is very small.