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Help, 3D Physics question...

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Hello I am trying to do a simple simulation of a Ball moveing over a surface like a pool game (WITHOUT Friction, so no rotation here), but the only difference with a pool table is that my table has slopes, so my trouble is as follows: First I know that to program some real physics I need to calculate all the Forces acting over my ball's center of mass and then get the acceleration with a = F / m, so then I integrate this accel an get velocity so integrate then and I get my pos. So for my ball rolling a Plane Table without slopes I use: Fy = N - W = 0 (Where N = Normal Force, and W = mg) Fx = F (Where F = Impulse force) But when I am in a slope I know that I must get the Normal and W components based in the slope angle, but I really dont know how to compute this with vector math? I really appreciate any help with this. Thanks Oscar Edited by - ogracian on June 12, 2001 7:20:24 PM Edited by - ogracian on June 12, 2001 7:23:32 PM

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I'm currently doing exactly the same thing : a ball rolling on an uneven ground.

First you calculate the 'Free' Forces.
Weight W = mg and Impulse F = whatever you want.

N is the normal to your slope. (careful, I'm not using your notations here )

The reaction of the Table is f+R, where :
1. f is friction (parallel to the slope) ( in this case f=0 )
2. R is perpendicular to the ground, ( ie. R = k * N, with k being a float )
3. R+W+F is parallel to the ground. i.e. (R+W+F).N = 0
( . is the dot product )

3 and 2 give : (W+F).N = - R.N = -k
back into 3 : R = -((W+F).N)*N

Finally : R+W+F = W+F -((W+F).N)*N

And that's the sum of all forces.
I hope this helps, but if you want, I can post some code.

Edited by - Thibault on June 13, 2001 5:36:07 AM

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Hello, and thanks so much for your help, that was exactly what I was looking for!. By other Hand, I really appreciate so much if you could post some code

For Last, if I want to add friction force to my simulation, could you tell me how can this be added to the equation?, this is because I will try to add some ball's rotation.

Best Regards!
Oscar

Edited by - ogracian on June 13, 2001 11:53:59 PM

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