[vtk-developers] transparent foreground polygons occluding background geometry

[Brad Hollister]

Hi,

We have a problem with transparent foreground polys occluding 
geometry.

We're trying to use depth peeling to handle foreground polygons with 
transparency. However, while depth peeling is enabled, 
GetLastRenderingUsedDepthPeeling() returns false.

(The polygons also intersect other similar polygons so that some parts 
of them are in front of others, while other parts of the same poly may 
be behind others. Another reason to use depth peeling as opposed to 
depth sorting, in our opinion.)

We also require custom shaders, using 
vtkOpenGLPolyDataMapper::SetVertexShader(), etc. From the test code @ 
http://www.vtk.org/gitweb?p=VTK.git;a=blob;f=Rendering/OpenGL2/Testing/Cxx/TestUserShader2.cxx, 
it looks as though custom shaders can't be used with depth peeling in 
VTK.

Thus, is there another way to enable depth peeling or to have 
transparent foreground polys in our usage scenario?

Regards,
Brad