ConvexCollisionCalculateVolume after ReleaseCollision

[ledahut]

I would like to know if calling NewtonConvexCollisionCalculateVolume or NewtonConvexCollisionCalculateInertialMatrix with a pointer of Newton Collision, after this collision was released, could crash. Because for the moment it didn't.

Ex:
[FCollision=Pointer]

FCollision=NewtonCreateBox(world, 1, 1, 1, 0, nil);
NewtonBodySetCollision(FNewtonBody, FCollision);
NewtonReleaseCollision(world, FCollision);

FVolume = NewtonConvexCollisionCalculateVolume(FCollision);
NewtonConvexCollisionCalculateInertialMatrix(FCollision, @inertia,@origin);
...
Or should I release FCollision after volume and inertial calculs?

[Julio Jerez]

Code: Select all

FCollision=NewtonCreateBox(world, 1, 1, 1, 0, nil);   // ref = 2 (1 for the world cache one for create
NewtonBodySetCollision(FNewtonBody, FCollision);    // ref = 3 (body get one ref)
NewtonReleaseCollision(world, FCollision);               // ref = 2 (you create call)

FVolume = NewtonConvexCollisionCalculateVolume(FCollision);  // fine colliosn is alive

Newton DestoyBody(body)  // Ref = 0 collsion destroyed

[Delfi]

NewtonBodySetCollision(FNewtonBody, FCollision);

That is still keeping reference counter up.. until you destroy the body it's fine.

[ledahut]

Calling calculateXXX after ReleaseCollision of a compound crash.

Code: Select all

1/Create Null collision
    FCollision := NewtonCreateNull(Manager.NewtonWorld);

2/Create Body with Null collision an release it
    FNewtonBody := NewtonCreateBody(Manager.NewtonWorld, FCollision);
    NewtonReleaseCollision(Manager.NewtonWorld, FCollision);

3/Create CompoundCollision
    FCollision := NewtonCreateCompoundCollision(Manager.NewtonWorld,
      Length(FCollisionArray), FCollisionArray, 0); //Of course my application release  each Collision in FCollisionArray after that

4/Set it to my null body
NewtonBodySetCollision(FNewtonBody, FCollision);
NewtonReleaseCollision(Manager.NewtonWorld, FCollision); <-- if I comment this line for compound, it calculateXXX work

5/Calculate
// FCollision:=  NewtonBodyGetCollision(FNewtonBody); <-- Or I can uncomment this line
    FVolume := NewtonConvexCollisionCalculateVolume(FCollision);
    NewtonConvexCollisionCalculateInertialMatrix(FCollision, @inertia, @origin);

(I need to check reference count).

[Julio Jerez]

Compound collision are no cached.
if that was teh last ref the teh object is destroyed

you can call GetInfo to see if teh Ref count is larger than 1 before relasing the shape
if it is 2 or lower it mean it will be destroyed if it is a cached mesh.

[ledahut]

Thank you I have fixed that.

For others I explain with your exemple:

Code: Select all

FCollision=NewtonCreateCompoundCollision(blablabla); // ref = 1
NewtonBodySetCollision(FNewtonBody, FCollision);    // ref = 1 (body don't get one ref because Compound is not 'cached')
NewtonReleaseCollision(world, FCollision);               // ref = 0

FVolume = NewtonConvexCollisionCalculateVolume(FCollision);  // crash collision is dead