Scale messing with collision

[lewd]

So I've got a bunch of simple primitives in a scene, and I'm throwing scaled versions of those primitives at them. I scale them with SetCollisionScale and give them an initial velocity with SetVelocity.

The scaled objects appear to have a size of a single point, until their first collision. They miss other objects around the edges and only collide with the center. After one collision, they start behaving normally.

This only happens when scale is being messed with. Projectiles with a scale of 1 do not miss their collisions. Is this a bug or is there more to scaling objects than just calling this one function?

[JernejL]

SetCollisionScale should work, as long as the collision object is not shared among multiple bodies and another object is overriding scale, can you check that?

[Julio Jerez]

not, set scale work with share collision. collision are instances.

my guess is that you collsion shape are off. try implementing debug display,

[lewd]

What kind of debug display? I do not see an API for this anywhere.
I can only use extern C functions from the library.

[Julio Jerez]

the engine does not have any rendering function, instead is have low level functions that you can call to do what you want. you can see many example in file ..\applications\demosSandbox\sdkDemos\toolBox\DebugDisplay.h

look for function
void DebugRenderWorldCollision (const NewtonWorld* const world, DEBUG_DRAW_MODE mode)

if you play the demos, there is a drop down menu, that you can select to show the collision shapes.
from there you can see how the debug display is impediment.

[lewd]

Oh okay, I can reimplement that on my side.

[lewd]

Well, this is interesting. The colliders are scaled twice, and this is what's causing them to miss collisions the first time. But after that first collision, the scale is corrected, while debug still displays a smaller collider.
Bug?

[Dave Gravel]

Hi lewd,
Do you use scaled matrix somewhere in newton ?
Maybe i'm wrong but it look like you use a scaled matrix and with newton you need to use normal matrix without scale.