Q: 2.x NewtonCreateCompoundCollision()

[Van]

We are studying the NewtonCreateCompoundCollision(). The documentation is a little shy.

What sub-collision types are acceptable? Any type or is it limited to primitives? Can they be convex? Can they be Tree?

[Carli]

yes, that's a good question.
I'm planning to integrate Newton into a Script Engine and so I have to introduce 2 Datatypes: One that is a universal collision (for creating bodies) and one is a simple collision (for creating bodies _and_ for creating compound collisions (that are universal collisions))

[Stucuk]

Compound Collisions are for adding other already created Collision's into one collision. Basicaly you create collisions with NewtonCreateBox(Or any of the others. Doesn't have to be just one type of collision object) for example, put the collision pointer you get from them in an array, and then send it to NewtonCreateCompoundCollision which will join them all up into one Collision Object.

Note: I don't know if you can use Tree Collisions and the regular (Movable) collision types in a compound collision at the same time.

[Julio Jerez]

compound collison take all of the closed shapes collision.

you can not add collision tres, terrains, or user collision since this can only be static

[JernejL]

I've updated the NewtonCreateCompoundCollision wiki page using existing text there and some topics from the forum.
Hopefully i cleared up any issues about using this most awesome newton functionality

[Julio Jerez]

Delfi you may wan to fix this in teh forum

compound collisions in old version (pre-2.0) were instance objects that could not be shared among other rigid bodies. In Newton 2.0, this is no longer an issue - compound collisions may be reused/shared by multiple rigid bodies just like any other collision object.

in 2.0 compound collision are still isnacen object, but the fution create body make a copy of teh supahe tha was pass in.
Basically teh collision shape that is a signe to teh body is a copy o fteh compound collision.
an applictaion that keep to track collision shapes should get the collision pointer from the Body afet teh create the body, and not rely on the collision they are passing to the function create body.

but doing this Compounds work the same way as shared collision.

[JernejL]

Ok, i added this info to wiki, i thought the collisions were same.. as i was using this in my spaceships game and there was absolutely no slowdown or whatever when creating multiple bodies using same compound collision.

[Julio Jerez]

the auter layer is different,
with the new change I made thes is no nessesary,
however now that I am wroking in the destritible, it goes back to the same dilema,
you if you make for exampel tow buildings wih the same collision then destruing one will do teh same to teh oether.

so the most flexible sultion is to share what is important like the leaves nodes that contain the convex shapes, and make a copy of teh nodes that are just pointers that supports the data.
It seems to be efficient that way.
also starting from 2.09 compound collision are much more effiecent than they has ever being.