merge compound collision on runtime

[Michael]

Hey guys,
i'm stuck with my compound collision, maybe you could help me easily...
I want to glue some bodies together during runtime. At the moment I am using a slider with limits, but thats no good solution.
I tried to use a compound but its not working. I can create the compound collision object, but then every single convex hull is at the same position because the information about the relative offset is lost.
The positions of those single bodies which should be attached is not known until runtime.
Can somebody explain to me how to move parts of the compound?

And, by the way, do I have to destroy the old bodies? I would like to keep them updated by Newton, as the graphics are connected to them.

thanks!

[Michael]

Ah I just found the functions NewtonCreateConvexHullModifier which is what I was looking for...

[JernejL]

Hey guys,
I tried to use a compound but its not working. I can create the compound collision object, but then every single convex hull is at the same position because the information about the relative offset is lost.
The positions of those single bodies which should be attached is not known until runtime.
Can somebody explain to me how to move parts of the compound?

See: NewtonCollisionGetInfo, the m_offsetMatrix there is what you are looking for (you can call it on separate compound pieces, which can be also obtained using the NewtonCollisionGetInfo call)

[Michael]

yes that also works, thanks!

[Aphex]

Note that physical interactions with the moving parts will not be simulated correctly.

[Michael]

what do you mean?

[Aphex]

You're just moving the parts simply by changing their orientation matrix, not by using forces or imparting velocity. Physics engines can't work out correct physical interactions without these so you'd get penetrations and strange behaviour.
To get the expected behaviour you'd need to have separate bodies joined with constraints.

[Michael]

oh I think you got me wrong.. I just move the collision object once when I create the compound collision to fix them at the correct position. Otherwise they would all sit in the origin. I think this problem is solved (in two easy ways).