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ckeyes888
10-26-2018, 11:27 AM
Having some fun getting into Bullet dynamics but canít seem to keep objects from breaking apart
when colliding.
Hoping there is a setting Iíve missed to keep them together.
The scene and objects are simple with a key on a ring dropping on to a logo. Works and looks
great so far but the key breaks from the ring regardless of the mass or glue settings.

Any help very much appreciated.

Thanks,

Carl

MonroePoteet
10-26-2018, 03:04 PM
It sounds like the Bullet collision detection is failing because either the geometry(s) are not dense enough or the "Dynamics Framerate" in the Bullet=>World tab isn't high enough. Try increasing the Dynamics Framerate in the Bullet=>World tab to a high number (like 600fps), which allows Bullet to use fractional frames for detecting geometry collisions. You might also subdivide your key and / or keyring geometry to give more points / edges for collision detection to work with.

You might also have luck using "Convex Pieces" for the Bullet Parts Body (the key and keyring object) rather than Mesh.

mTp

ckeyes888
10-26-2018, 03:35 PM
Thanks. I did make some progress changing things you suggested but it still seems pretty much a crap shoot
what actually happens.

jwiede
10-26-2018, 04:14 PM
Thanks. I did make some progress changing things you suggested but it still seems pretty much a crap shoot
what actually happens.

Check to make sure the collision margin distance is small enough to recognize there's open space between key and ring. If too large, it won't see the bodies as distinct where the ring penetrates the key, and will treat them as overlapping.

For demo: Look at attached scene, note collision distance (50mm) and size of space between "key" and "keybar". Change collision margin to 1m and then see what happens.

143221

ckeyes888
10-26-2018, 08:47 PM
Thanks a bunch for all the help. Got it working pretty well.

Carl