Physical simulation - why does it break through the ground?

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Physical simulation - why does it break through the ground? // Roundtable

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Post by davidjohnson // Mar 10, 2009, 4:47pm

davidjohnson
Total Posts: 169
I am simulating a piece of paper dropping from the sky onto the ground. The simulation works fine, but as it hits the ground, it disappears into the ground, showing half of the paper. I am not sure how to fix this - any ideas?

I have tried with the 7.6 and 6.6 and I am getting the same thing. Any ideas?

Post by spacekdet // Mar 10, 2009, 4:59pm

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Quad-divide the floor object a few times (or quad divide the area where the paper hits). More geometry=more precise calculations.

Is the floor exactly at Z=0?

Post by Burnart // Mar 10, 2009, 5:00pm

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Increase the polygon resolution of the paper object. Also, if the paper object is a one sided plane you would be better off using a form developed from a cube.


Not sure if this applies to both workspace and modelside but in 6.6/modelside you can select for physics collisions to be based on vertices, faces or vertices and faces.

Post by Finis // Mar 10, 2009, 5:24pm

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In the Splododyne Explodiatory Explodolator project I had the same problem. Someone, Spacekdet?, recommended that I give the ground object physics properties. When I did that the sinking was fixed and I didn't have to subdivide.


I agree with Burnart about making the paper from a cube.

Post by davidjohnson // Mar 10, 2009, 5:41pm

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Yes, after experimenting, I figured out the quad divide part. Now I am trying to sort out how to creating falling paper that DOES NOT bounce! It is really weird, you would think that a physical simulation of falling paper wouldn't bounce, but when another piece of falling paper hits it, it bounces all over the place! What do most people do to prevent this?

Post by Jack Edwards // Mar 10, 2009, 5:53pm

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You could try simulating it as a stiff cloth.
To avoid the plane and ground plane occupying the same space move your ground plane slighting below z=0.

Post by Finis // Mar 11, 2009, 7:41am

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Model side:

Here's a quick paper animation. The objects remain in the final positions at least the few seconds I watched beyond the end of the movie. Needs tuning to look right but addresses the bouncing paper issue. The objects are simple with no extra subdivision although some is sometimes needed. The paper stats are in the image and the ground has physics properties: Elasticity: 0 resist: 300 fric: 100 coarse: 100 charge: 0 adhes: 1. Works well with straight default wood properties for the ground too.

Elasticity is the main thing for bouncing. An elastic collision, high elasticity, is like billiard balls colliding. Low elasticity is like two towels colliding. Friction and adhesion are the best tools to stop the wiggling and sliding but the spinning seems almost impossible to stop.

Post by spacekdet // Mar 11, 2009, 7:54am

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Be sure you're actually using paper and not these:

18857

Post by v3rd3 // Mar 11, 2009, 9:18am

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@spacekdet :D
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