Collision Callback has no userdata in V2B17?

[saxman]

I'm setting the userdata field as so...

NewtonMaterialSetCollisionCallback( newtonWorld_, newtonMatId1_, newtonMatId2_, newtonData_, NULL, newtonContactsProcess );

But in my newtonContactsProcess function, the userdata is NULL...

newtonContactsProcess( const NewtonJoint *newtonJoint, dFloat newtonStep, int newtonThreadId )
{
void *newtonData = NewtonJointGetUserData( newtonJoint );

Is this a bug or is there another way to get the userdata set with NewtonMaterialSetCollisionCallback?

[Gianluca]

It's your error !!

In fact, you setted the user data into the NewtonMaterialSetcollisionCallback... so, the userdata is regarding the material (NewtonMaterial).

But in your code after, you request the userdata to the joint (NewtonJointGetUserData) and you never setted it.
Instead, you have to use the NewtonMaterialGetUserData in the following way:

Code: Select all

void newtonContactsProcess( const NewtonJoint* contactJointList, dFloat timestep, int threadIndex ) {
   for( void* contact = NewtonContactJointGetFirstContact( contactJointList ); contact; contact = NewtonContactJointGetNextContact( contactJointList, contact ) ) {
      NewtonMaterial* material = NewtonContactGetMaterial( contact );
      YourData* data = (YourData*)( NewtonMaterialGetMaterialPairUserData( material ) );
}


[saxman]

Since Newton is often wrapped in a C++ class, it would be much more helpful to get the userdata first thing, rather than having to iterate through a for loop to find it. In my case, I need access to the class before I start processing any collisions.

I ended up with...

const NewtonBody *newtonBody0 = NewtonJointGetBody0( newtonJoint );
NewtonWorld *newtonWorld = NewtonBodyGetWorld( newtonBody0 );
void *newtonData = NewtonWorldGetUserData( newtonWorld ;

[JernejL]

If i'm not mistaken, NewtonContactJointGetFirstContact and NewtonContactJointGetNextContact actually iterate thru ALL contacts with all different materials in one callback, that's why you have to iterate them all to get all user data for all the unique material pairs.

Julio please correct me if i am wrong.

[saxman]

Hmm, a couple of the samples (BasicFriction/BasicRestitution) make reference to...

body0 = NewtonJointGetBody0(contactJoint);
body1 = NewtonJointGetBody1(contactJoint);

and even...

node = (RenderPrimitive*) NewtonBodyGetUserData (body);

but it would be good to know if I am understanding this incorrectly.

[Julio Jerez]

look at teh demo that shwo teh track tanks they use the callback in many ways.
The callback now are much more flaxible thet they were in 1.53

plus you also can use the engine without using callback, after an update you can use the ietrator to collect the information you need.