[vtk-developers] vtkLODProp3D and vtkProp3D:SetUserTransform ? (+ GetActors bug ?)

[David Gobbi]

I can't answer all the questions here, but I'll take a stab at some of
them:

On Mon, 17 Jul 2000, Sebastien BARRE wrote:

> I was wondering if the vtkLODProp3D might be seen as a kind of assembly ?
> 
> If it's the case, wouldn't it be logical that, being a subclass of 
> vtkProp3D, a vtkLODProp3D should propage the UserTransform as an assembly 
> does ? Modifying the UserTransform would automatically modify the aspect of 
> the objects in the LODProp3D, as it is implemented for an assembly (in the 
> current CVS, doing so on the LODProp3D does not affect anything).

This seems to make sense.

> I know that I might use the UserMatrix, the I found the UserTransform more 
> powerful most of the time.

Yeah, that's why I added SetUserTransform a few months back. 

> Here is the beginning of the implementation :
> 
> // The real method for adding an actor LOD.
> int vtkLODProp3D::AddLOD( vtkMapper *m, vtkProperty *p,
> 			  vtkTexture *t, float time )
> {
>    int          index;
>    vtkActor     *actor;
>    vtkMatrix4x4 *matrix;
> 
>    index = this->GetNextEntryIndex();
> 
>    actor = vtkActor::New();
>    matrix = vtkMatrix4x4::New();
>    this->GetMatrix(matrix);
>    actor->SetUserMatrix(matrix);
>    matrix->Delete();
>    actor->SetMapper( m );
> 
> The UserMatrix is shared I guess, but it's missing the UserTransform, am I 
> right ? Something like :
> 
> actor->SetUserTransform(this->GetUserTransform());
> 
> Am I missing a point somewhere ?

The UserTransform and UserMatrix _should_ be unified, i.e. they should
always be the same transformation.  Right now, they aren't... I was 
waiting for the new Assembly code to stabilize before unifying the
UserTransform and UserMatrix.  I'll look into it sometime soon, I 
already know exactly what has to be done.

 - David


> For the moment, I could correct this by adding some mapper/property 
> combination to the LODProp3D, then browse the collection of prop3D that 
> were internally created by the LODProp3D, and set their UserTransform.
> Sadly, there is no way to get this collection of prop3D. The 
> LODProp3D::GetActors is documented as :
> 
> "For some exporters and other other operations we must be able to collect 
> all the actors or volumes. These methods are used in that process."
> 
> But this is not what happens. Here is the beginning of the code :
> 
> void vtkLODProp3D::GetActors(vtkPropCollection *ac)
> {
>    vtkDebugMacro(<< "vtkLODProp3D::GetActors");
>    int index = 0;
>    if (this->AutomaticPickLODSelection)
>      {
>      if ( this->SelectedLODIndex < 0 ||
> 	this->SelectedLODIndex >= this->NumberOfEntries )
>        {
>        index = this->GetAutomaticPickPropIndex();
>        }
>      else
>        {
>        index = this->SelectedLODIndex;
>        }
>      if (! this->LODs[index].Prop3D->IsA("vtkVolume"))
>        {
>        ac->AddItem(this->LODs[index].Prop3D);
>        }
>      }
> 
> => I might be wrong, but GetActors() seems to have been written so that :
> 	a) only the prop that shall be used for the given estimated time will be 
> returned
> 	b) NO vtkVolume !
> 
> My question : is that behaviour OK ? I guess LODProp3D was mainly 
> introduced to handle volume rendering issues, therefore is there any 
> rational for b) ? Should we add a method to get real access to every prop3D 
> that have been created internally ?
> 
> Thanks 
> 
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