[ENH] vtkProp3D : UserMatrix : pre/post concatenation flag ?

[Sebastien Barre]

Hi

I was wondering if it would be possible to add a flag to control how the
UserMatrix of a Prop3D is concatenated with the current Prop3D's own matrix.

Here is the actual code (graphics/vtkProp3D.cxx) :

void vtkProp3D::GetMatrix(double result[16])
{
  // check whether or not need to rebuild the matrix
  if ( this->GetMTime() > this->MatrixMTime )
    {
    this->GetOrientation();
    this->Transform->Push();  
    this->Transform->Identity();  
    this->Transform->PostMultiply();  
    
    // shift back to actor's origin
[...]
    // scale
[...]
    // rotate
[...]
    // move back from origin and translate
[...]
    // apply user defined matrix last if there is one 
    if (this->UserMatrix)
      {
      this->Transform->Concatenate(this->UserMatrix);
      }
    this->Transform->PreMultiply();  
[...]
} 

As one can see, there is no way to control the concatenation of the user
matrix, it is set to PostMultiply. Maybe adding two members like
PostMultiplyUserMatrix,  PostMultiplyUserMatrix ?

    // apply user defined matrix last if there is one 
    if (this->UserMatrix)
      {
      if (this->PreMultiplyFlag != 0) {
         this->Transform->PreMultiply();  
     }
      this->Transform->Concatenate(this->UserMatrix);
      }

Does it look stupid or break some design issues ? There is sometimes when
I'd like a transform common to many actors to take place, then a specific
transform to happen for a specific actor (in that order).

Thanks


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