jointTransform.cpp

// using first frame for testing
Skeleton* frame0 = rest_animation->GetFrame(0);

// for each joint in skeleton...
for (int i = 0; i < frame0->NumJoints(); i++) {
  // current joint
  Joint jnt = frame0->GetJoint(i);
  // "global" transformation that should be applied to current joint
  Matrix_4x4 totalTransform = Matrix_4x4::Id();
  
  // start at parent, transformation for current joint will be applied after loop
  int currentId = jnt.parent_id;
  while(currentId >= 0){    
    // current parent joint
    Joint parentJnt = frame0->GetJoint(currentId);
    
    // function returns TransformationMatrix of current parent joint: rotation * position 
    Matrix_4x4 trans = parentJnt.GetTransform();
    // accumulate transformations
    totalTransform = trans * totalTransform;
    
    // get next parent
    currentId = parentJnt.parent_id;
  }
  // finally apply totalTransform to current joint
  Vector3 newPos = totalTransform * jnt.rotation * jnt.position;
}