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JaydenDP

Bullet collisions

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Hi!

I'm having a problem with bullet collisions, hopefully someone here could shed some light on it for me.

If I have an animated cache colliding with fractured geometry, the interaction seems very unnatural. This is when loading the cache as a static object with deforming on.

If I replicate that object with an active RBD instead, and initialize the velocities in DOPS, the collision works much more realistically.

Now I know this is a common problem, but are there any general tips for getting static deforming cached geometry to treat and interact with bullet objects in a way that better matches using a DOP object with initial velocity?

Thanks in advance!

Jay

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I mean, its not drastically different! But there's obviously the issue with how its treating the mass of colliding objects, especially when pre-animated geometry is a completely unstoppable force...hmm

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Static objects are treated as having infinite mass, so you will see different collision behaviour in the two cases.

You might want to try turning off the Split Impulse setting on the solver, though. Animated static objects essentially "teleport" to their new position on each frame, which can cause them to interpenetrate other objects. If Split Impulse is enabled and the penetration distance is greater than the Penetration Threshold, the solver will separate the two objects without adding any additional velocity.

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everything everyone has said is spot on. Animated static objects are basically popping into place each frame. There's no interpolation. It may help to append a timewarp sop to your cache, with "interger frames' unticked, and $FF instead of $F for the frame expression. Then up the substeps on the dopnet itself. That way, at least your feeding interpolated data into the static object, so the substepping will be more accurate.

Also, scene scale is not very important, and obviously animated static objects have no mass. So a really big dynamic chunk hitting a really small animated static object is gonna look really weird in regards to mass.

also try not using static solver, and just use an rbd object, or fracture object, turn off 'create active object', and turn on 'use deforming geometry', and feed that through the bullet solver with all the active objects.

Edited by substep

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