Ah! Now you are getting into murky waters :). Volume rendering together with translucent geometry is difficult thing to do with OpenGL. You need a full fledged ray-tracer for that to work correctly. You are correct, in VTK/ParaView, the geometries are rendered (including translucent geometry) before volume. Since translucent geometry does not affect Z-buffer as opaque geometry (what's the depth for a translucent pixel, really?), the volume mapper cannot correctly determine when to stop the ray tracing and hence the issues.
Utkarsh On Fri, Jun 24, 2011 at 4:41 PM, Gary Strangman <gary.strang...@gmail.com> wrote: > Hi Utkarsh, > Half-progress. So, I can display a variable-transparency volume rendering > (in this case of a head MRI, set so that the 0s around the head are > transparent). I can then add a .vtk surface, and I can sorta see "both" > datasets when opacity on the surface is set to 1.00 ... the grayscale volume > peeks through at various points of the overlying (colorized) surface. I'd > like to be able to see more of the underlying volume, so I reduce the > opacity value for the surface. However, for any opacity value < 1.00, > paraview renders only the /back/ side of the surface (the part of the > surface on the other side of the head from the camera viewpoint) ... the > foreground portion disappears completely. After playing around with > translations, I'd guess that for opacity<1.00 the volume is entirely > rendered last, overwriting what should be foreground surface pixels. Does > that make any sense? Perhaps I need to show a picture ... > -best > Gary > > Gray, > > Currently ParaView supports changing the opacity in colormaps only for > volume rendering. When rending slice or points as surface or anything > other than volume, opacity will be fixed to single value that can be > set on the Display tab. > > Utkarsh > > On Mon, Jun 20, 2011 at 4:30 PM, Gary Strangman > <gary.strang...@gmail.com> wrote: >> Hi again all, >> I solved my linked-colormap problem when rendering multiple volumes >> (thanks >> Utkarsh, using separate variable names worked great!). My next issue is >> this: can someone explain when colormap transparency is enabled? In some >> of >> my data views, the opacity option is grayed out (for example, in slice >> renderings, and also in points data). I kinda understand the points case, >> but I was surprised by slice renderings. I suspect there is an underlying >> principle I'm missing here ... >> -best >> Gary > _______________________________________________ > Powered by www.kitware.com > > Visit other Kitware open-source projects at > http://www.kitware.com/opensource/opensource.html > > Please keep messages on-topic and check the ParaView Wiki at: > http://paraview.org/Wiki/ParaView > > Follow this link to subscribe/unsubscribe: > http://www.paraview.org/mailman/listinfo/paraview > > _______________________________________________ Powered by www.kitware.com Visit other Kitware open-source projects at http://www.kitware.com/opensource/opensource.html Please keep messages on-topic and check the ParaView Wiki at: http://paraview.org/Wiki/ParaView Follow this link to subscribe/unsubscribe: http://www.paraview.org/mailman/listinfo/paraview
