[vtkusers] depth sorting problems?

[Aashish Chaudhary]

If your hardware has proper extensions you could use

Depth peeling:

http://www.itk.org/Wiki/VTK/Depth_Peeling
http://www.vtk.org/Wiki/VTK/Examples/Cxx/Visualization/CorrectlyRenderingTranslucentGeometry



On Tue, May 10, 2011 at 12:32 PM, Steven Chall <stevec at renci.org> wrote:
> Please look at the attached images, showing two sets of structures
> (vtkPolyData objects) constructed inside a loop using the code included
> below.  I strongly believe that the code for the two images is identical
> except that actor->GetProperty()->SetOpacity(…) is being called for
> c113_transparent.png with an argument < 1.0.
>
>
>
> c113_opaque.png  (opacity == 1.0) looks ok.  But c113_transparent.png
> (opacity < 1.0) has various kinds of ugly rendering artifacts that show up
> when opacity isn’t all the way on, maybe sorting errors?   Also, note that
> the ordering of the structures is wrong front-to-back when opacity is less
> than full:  for example, the brown structure appears to be in front of the
> red and dark gray ones, but it’s not when opacity is full on (nor should it
> be).  I’m trying various combinations of normal parameter values, e.g.,
> flipped, not flipped, etc., but I haven’t found the right combination to
> make partial transparency acceptable.
>
>
>
> I’m running VTK 5.6.1 with Qt 4.7.1 in Win7 Enterprise, all 32 bits, on a
> ThinkPad with a 1.6 GHz i7 (Q720) cpu and 4 GB RAM. Thanks for any
> suggestions.
>
>
>
> -Steve
>
>
>
> vtkPoints *points = vtkPoints::New();
>
>
>
>     //…read in a bunch of vertices…
>
>
>
>   vtkCellArray *polys = vtkCellArray::New();
>
>
>
>     // …likewise read in a bunch of edges to connect the vertices…
>
>
>
>   if (structure) structure->Delete();
>
>   structure = vtkPolyData::New();
>
>   structure->SetPoints(points);
>
>   points->Delete();
>
>   structure->SetPolys(polys);
>
>   polys->Delete();
>
>
>
>   if (deci) deci->Delete();
>
>   deci = vtkDecimatePro::New();
>
>   deci->SetInput(structure);
>
>   deci->SetTargetReduction(0.5);
>
>   deci->PreserveTopologyOn();
>
>
>
>   if (smoother) smoother->Delete();
>
>   smoother = vtkSmoothPolyDataFilter::New();
>
>   smoother->SetInputConnection(deci->GetOutputPort());
>
>   smoother->SetNumberOfIterations(100);
>
>
>
>   if (normals) normals->Delete();
>
>   normals = vtkPolyDataNormals::New();
>
>   normals->SetInputConnection(smoother->GetOutputPort());
>
>   normals->FlipNormalsOn();
>
>  normals->AutoOrientNormalsOn();
>
>   normals->NonManifoldTraversalOff();
>
>   normals->ConsistencyOn();
>
>   //normals->ComputeCellNormalsOn();
>
>
>
>   if (mapper) mapper->Delete();
>
>   mapper = vtkPolyDataMapper::New();
>
>   mapper->SetInputConnection(normals->GetOutputPort());
>
>
>
>   if (actor) actor->Delete();
>
>   actor = vtkActor::New();
>
>   actor->SetMapper(mapper);
>
>   actor->GetProperty()->SetInterpolationToPhong();
>
>
>
>   if (transparency != 0.0)
>
>   {
>
>     //normals->FlipNormalsOff();
>
>     actor->GetProperty()->SetOpacity(1.0 - (transparency / 100.0));
>
>   }
>
>
>
>   actor->GetProperty()->SetSpecular(4);
>
>   actor->GetProperty()->SetSpecularPower(30);
>
>   actor->GetProperty()->SetColor(clr[0], clr[1], clr[2]);
>
>   actor->GetProperty()->SetSpecularColor(1, 1, 1);
>
>
>
>   renderer->AddActor(actor);
>
>
>
>
>
>
>
> -Steve Chall
>
>  Senior Research Software Developer
>
>  Renaissance Computing Institute (RENCI)
>
>  Phone: 919-681-9639
>
>  Email: stevec at renci.org
>
>
>
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-- 
| Aashish Chaudhary
| R&D Engineer
| Kitware Inc.
| www.kitware.com