User Data Problem.

[Auradrummer]

Hello guys,

I'm trying to assign a integer as UserData and then attach it to a body, to be able to get it on the Callbacks.

In the same .cpp where the body is created I put this piece of code and worked well.

Code: Select all

   userData = &ID;
   NewtonBodySetUserData(suspension[ID].body, userData);
   int * test;
   test = (int *) NewtonBodyGetUserData (suspension[ID].body);
   printf ("User data %u \n", *test);


But, the same code inside the CallBack (that is in another .cpp), the printed value was crazy. Any tip?

Thanks

[Julio Jerez]

make sure it is teh same body.

[Auradrummer]

Hi Master,

Yes, is the same body, because I get the mass using the GetMassMatrix and I received the exact value I assign.

[Auradrummer]

The crazy value that is shown is changing every time I run the program...

[martinsm]

It's better to store integer by value, not by pointer:

Code: Select all

userData = (void*)ID;
NewtonBodySetUserData(suspension[ID].body, userData);

int test;
test = (int)NewtonBodyGetUserData(suspension[ID].body);
printf ("User data %u \n", test);

Integer value can change location in memory so you must be careful when storing pointer to it. But in value case you don't care about how and where in memory value resides.

[Auradrummer]

Very creative solution.
If I understood well, you passed the value of the variable 'ID' as it was a memory address. So, further, I get this 'memory address' back, and recover the integer value. Very good.

The only thing I had to mention is that (void*) pointer didn't work. I got the message 'cannot convert *void to *int'. So, I declared the pointer as (int *) and I recovered it at the Callback without problems.

Thanks very much, I think this tip is very useful to a large number of people.