[vtkusers] Any alternative to vtkUnstructuredGridVolumeRayCastMapper

[Moreland, Kenneth]

1) Pretty soon (in the next week or two) I plan to check in a projected
tetrahedra mapper.  That should be faster, but of lower image quality.
Of course, if you are not using the CVS version of VTK, that will not
help for quite a while.
 
2) Hmm, that "wireframe" artifact looks like a bad ray integration.  Are
you using VTK 4.4 or the CVS version?  The integration has gotten much
better since the last VTK release.
 
Those artifacts can be made less pronounced by making the transfer
function less opaque and/or making the colors change more slowly.  If
that area where the volume changes from yellow to red is interesting,
you may want to consider putting a red isosurface there and then render
a yellow volume around that.  The result will probably look quite
pleasing and may speed up the rendering a bit.
 
3) Your suggestion of sampling the volume to an image is viable.  That
was what many people did before vtkUnstructuredGridVolumeRayCastMapper
was around (which was not very long ago).  I never did it, so I can't
offer any details.  Maybe someone else can chime in.
 
-Ken
 
   ****      Kenneth Moreland
    ***      Sandia National Laboratories
*********** 
*** *** ***  email: kmorel at sandia.gov
**  ***  **  phone: (505) 844-8919
    ***      fax:   (505) 845-0833



________________________________

	From: vtkusers-bounces at vtk.org [mailto:vtkusers-bounces at vtk.org]
On Behalf Of jiksed
	Sent: Thursday, April 14, 2005 1:19 PM
	To: vtkusers at vtk.org
	Subject: [vtkusers] Any alternative to
vtkUnstructuredGridVolumeRayCastMapper
	
	
	Hi vtkusers,
	 
	I have a 3D volume data in an unstructured grid with irregular
surface topography. My first
	 instinct is to use vtkUnstructuredGridVolumeRayCastMapper to do
the volume rendering. The
	 problem is that this volume mapper is extremely slow and the
wireframe-type mesh is visible 
	in the volume image (please see the attachment). My questions
would be:
	 
	1) Is there any way to speed it up? 
	2) How can I make the image more smooth without showing the
underline wireframe?
	3) Is there any alternative to
vtkUnstructuredGridVolumeRayCastMapper? I really need an 
	ImageData so I may manipulate the volume opacity and use the
ImagePlaneWidget.
	 
	One way I can think of is to use vtkShepardMethod to transform
vtkUnstructuredGrid into 
	vtkImageData in a rectangular box. My data is inside an
irregular volume like human head. 
	Now how do I "get rid of" excessive volume to expose my
irregular surface topography? How 
	do I manipulate the output of vtkShepardMethod? By setting a
small MaximumDistance, some 
	points may end up with NullValues but not those points close to
the outer surface of my data 
	volume. I am kind of lost here. 
	 
	Thank you for any suggestions.

	
________________________________

	Do you Yahoo!?
	Yahoo! Small Business - Try our new resources site!
<http://us.rd.yahoo.com/evt=31637/*http://smallbusiness.yahoo.com/resour
ces/>  

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.vtk.org/pipermail/vtkusers/attachments/20050414/8c9b6b96/attachment.htm>