[vtkusers] Draw one image on top of another

[John Drescher]

On Wed, Aug 31, 2011 at 1:17 PM, Artem Babayan
<artem.paraview at googlemail.com> wrote:
> Hello,
>
> I draw concentration distribution field over the map -- images for map
> and concentration fields are in the separate actors (vtkActor). I add
> these actors to the render window:
>
>         window->GetRenderers()->GetFirstRenderer()->AddActor(actor_map);
>         window->GetRenderers()->GetFirstRenderer()->AddActor(actor_field);
>
> However, two images gets mixed together -- instead of non-transparent
> parts of concentration field overwriting the map image they are shown
> together with pixels from the map going through the fields' pixels in
> some places. It happens regardless of the order I add actors to
> rendered. Is it a way to ensure, that image in actor_field is always
> on the top of actor_map?
>

I use the technique that is in the following example in my code:

http://www.vtk.org/Wiki/VTK/Examples/Cxx/Images/Transparency

John