[vtkusers] Depth peeling

Busse, Thomas (GE Oil & Gas) Thomas.Busse at ge.com
Mon Nov 10 03:48:34 EST 2014

Thanks a lot for help.

I have put a breakpoint at vtkOpenGLRenderer.cxx:541

The this->DepthPeelingIsSupported is 0.
Digging a little bit deeper this is because :

      GLint alphaBits;
      glGetIntegerv(GL_ALPHA_BITS, &alphaBits);
      int supportsAtLeast8AlphaBits=alphaBits>=8;

alphaBits is 0.

I have checked that all other conditions for
      this->DepthPeelingIsSupported =
        supports_depth_texture &&
        supports_shadow &&
        supports_blend_func_separate &&
        supports_shadow_funcs &&
        supports_vertex_shader &&
        supports_fragment_shader &&
        supports_shader_objects &&
        supports_occlusion_query &&
        supports_multitexture &&
        supports_GL_ARB_texture_rectangle &&
        supports_edge_clamp &&
        supportsAtLeast8AlphaBits &&

are true.

Do I have some settings wrong so that alphaBits is 0? Or is it a problem with my graphics card?

Best Regards,

From: David E DeMarle [mailto:dave.demarle at kitware.com]
Sent: Freitag, 7. November 2014 18:00
To: Busse, Thomas (GE Oil & Gas)
Cc: vtkusers at vtk.org
Subject: Re: [vtkusers] Depth peeling

There can be other conditions.

Need to more details (or sit down with a debugger) to know for sure if one of them is stopping you.

Put a breakpoint at vtkOpenGLRenderer.cxx:541 to see if vtk thinks your card can do depth peeling (or run one of the vtk depth peeling tests).

Put a breakpoint at vtkRenderer.cxx:599 to see if vtk thinks that there are translucent objects in your scene. The one has tripped me up before. If it is for you and you happen to be rendering multi block data with block opacity, try setting Mapper->SetScalarVisibilityOff to prevent the LUT from deciding.

David E DeMarle
Kitware, Inc.
R&D Engineer
21 Corporate Drive
Clifton Park, NY 12065-8662
Phone: 518-881-4909

On Fri, Nov 7, 2014 at 9:24 AM, Busse, Thomas (GE Oil & Gas) <Thomas.Busse at ge.com<mailto:Thomas.Busse at ge.com>> wrote:

I tried to get depth peeling working but without success until now.

My setup is VTK6.1 and a NVidia Quadro K300m under Windows.

Here is the code snippet of the initialization:

  m_pVtkRenderWindow = pVtkMFCWindow->GetRenderWindow();


  // Use Depth Peeling for transparency

but after rendering a call to
  int depthPeelingWasUsed = m_pVtkRenderer->GetLastRenderingUsedDepthPeeling();
returns 0.

Can someone help me on this?
Is there some additional trick required to get it working?

According specs the graphics card should fulfill all requirements.

Best Regards,

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