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Verlet Sliding Problem

Started by MrRhodes Sep 19, 2006 at 7:03 PM 2 replies 1k views

Original Post

Sep 19, 2006 at 7:03 PM

Hey Guys, Been viewing the forum for a while now, mostly been able to find what answers i could possibly need but now im at an end... I've been playing around with some verlet intergration things in 2d and i've run upon a problem when i create some complex shapes (such as a rigid circle), and i've noticed that when it hits a completely flat surface it starts to roll to one side, I'm guessing its down to the order of which i update particles or constraints between them... anyone any ideas of ways i can overcome this issue? Cheers. -Ste

Numsgil

109

Numsgil

Sep 19, 2006 at 10:05 PM

You want to be very careful that as you update your positions (constraints), you do not update using any of the new calculated positions.

For instance, say you update position 1 of a rigid body. If you then update position 2, it's going to use the new position for position 1, which is bad.

You can either update your rigid bodies in a random order each cycle, or keep a "temporary" position array and use that to store the new positions, then copy the new positions into the old positions after all calculations are finished.

Hope this makes sense, I'm typing in a state of mental fog :P

nataku92

Sep 19, 2006 at 10:31 PM

Quote:
Original post by oliii
that introduces drift. A quick bodge would be to satisfy constraints one way going up the list, and then next time the other way, going down the list.

I tried that, it reduces the drift a fair amount, but it's just a hack really. Resting the object properly would be the way to go.

what oliii suggested in this topic

It works very well, or at least in my case.

MrRhodes

Author

MrRhodes

Sep 23, 2006 at 7:20 AM

I've tried all sorts now..

the alternating order, the buffered positions.... and its still going walkies.. I create a soft body circle, it hits the floor and just walks to the right...

Any more suggestions?

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