If I create a group node I can’t assign a transformation matrix to node. I get every time error no matter the way:

For example the below code:

// Create the group node:

mgrec *groupRec = mgNewRec(fltGroup);

// Get the matrix record. It gives a valid pointer

mgrec *mat = mgGetAttRec(groupRec, fltMatrix, MG_NULL);

// Set the values contained in my grpMatrix to matrix attributes

int numElements = mgSetAttList(matrixRec,

fltMatrix00, grpMatrix(0,0),

...

...

fltMatrix33, grpMatrix(3,3),

MG_NULL );

I get numElements = 0 i.e. the mgSetAttList was not successful

if I try to use the command

mgbool ret = mgSetMatrix ( groupRec, fltMatrix, grpMatrix(0,0) );

I get ret = MG_FALSE

I would appreciate any help

You don't set a nodes matrix directly, instead you attach Transformation Records to the node as described in this previous forum thread:

support/discussions/topics/511

Also if you have OpenFlight 4.2 there is a FAQ describing this with sample code in the OpenFlight API Reference.

FAQ: How do I apply a matrix (transformation) to a node?

Thanks a lot !