NewtonCreateConvexHull and OffsetMatrix

[JulBaxter]

Is it for optimization purpose that OffsetMatrix is baked in NewtonCollision ?

Because NewtonCollision can be shared between NewtonBody, IMO it would be more flexible and powerful for end-users to set offestMatrix during NewtonCreateBody. Like that, the same NewtonCollision could be setup in different ways with each NewtonBody using it.

What do you think about that ?

[Julio Jerez]

That would be cool and I realized that it is a problem for some featores, but for Newton 2.0 that woudl be a too big of a job.

Now the offset matrix of a collision shape is part of the signature of the shape and that make it difficult to change it.

In fact there is a colilsion instance already that I used with the destruction shape but it is not exposed.
I found that problem when I realised that the collision shape need to store local data with the shape which that make sharing impossible.
on the other hand adding collision instance can be a big change that need a from the ground up refactoring, given the large number of shape there are in the engine.
Maybe for newton 3.0

Collision instance will be a generalization of the convex hull modifirer, that already exist in the enigne.
you can use that shape for what you want. and the use the matrix to relocate the shape.

[JulBaxter]

Do you want to say I can create NewtonCollisions with a NULL OffsetMatrix and then share it by creating ConvexHullModifier ? (i.e. different ConvexHullModofiers can reference the same NewtonCollision ? )

Does A = NewtonCreateConvexHullModifier( B ) increase the reference counter of B ?
Have I to call NewtonReleaseCollision on A ?

and finally what are the consequences to generalize the use of ConvexHullModifier for each Shape I put in a Body in term of memory charge and runtime performance ?

[Julio Jerez]

to use the modifier you make a collision, and the you can make as many modifier that use tha colliion as you want.

The consecunce of using a modifires is that it is a tow level of indirection, plus bacuase the matrix is a Ganeral matrix, it must use genral matrix for Invertiosn, and rotation,
some of the functional like Raycastinf cost a litle more because of the general matrix.
The cost is marginal, you cna use it for what you want.

[JulBaxter]

Thank you for your answers.