[vtkusers] vtkOpenGLHAVSVolumeMapper a problem or not ?

Alfredo Gourbish the.answer3 at libertysurf.fr
Wed Jul 18 18:53:27 EDT 2007

Ok ok... In fact I tried to find the fastest solution to render the volume. 
That's why I tested unstructured grid, but now, as you explained me that is 
not interesting to have unstructured data in order to have effectiveness, I 
will stop these tests...
Finally, I don't know if they are better rendering for structured points 
than vtkVolumeRayCastMapper or vtkFixedPointVolumeRayCastMapper. Do you know 
a better choice ?
And without wanting to misuse, I have another thing that I wanted to do ; 
extracting data from my volume. I tried some filters but I didn't succeed in 
extracting data.
I would have so much question to ask... :-)

Already, thank you for you answers Ken !


----- Original Message ----- 
From: "Moreland, Kenneth" <kmorel at sandia.gov>
To: "Alfredo Gourbish" <the.answer3 at libertysurf.fr>; "vtkusers" 
<vtkusers at vtk.org>
Sent: Thursday, July 19, 2007 12:27 AM
Subject: RE: [vtkusers] vtkOpenGLHAVSVolumeMapper a problem or not ?


In general, you do NOT want to convert your structured points to an
unstructured grid.  The structured arrangement provides implicit
connectivity that many algorithms, including volume rendering, can
exploit to provide much more efficient processing.  You will lose that
if you convert to an unstructured grid.

So, in the case of volume rendering, you will be much better off keeping
your data in a vtkStructuredPoints class and using one of the subclasses
of vtkVolumeMapper to do the volume rendering.


> -----Original Message-----
> From: Alfredo Gourbish [mailto:the.answer3 at libertysurf.fr]
> Sent: Wednesday, July 18, 2007 1:05 PM
> To: Moreland, Kenneth; vtkusers
> Subject: Re: [vtkusers] vtkOpenGLHAVSVolumeMapper a problem or not ?
> Okay, thanks you Ken for these explanations.  It's true that I have a
> structured data too. But now, I have another question : how can read
> images in order to write an unstructured grid ? For the moment, I read
> these
> images with ITK and write a VTK volume which is a "structuredpoints"
> Gourbish
> ----- Original Message -----
> From: "Moreland, Kenneth" <kmorel at sandia.gov>
> To: <the.answer3 at libertysurf.fr>; "vtkusers" <vtkusers at vtk.org>
> Sent: Wednesday, July 18, 2007 8:41 PM
> Subject: RE: [vtkusers] vtkOpenGLHAVSVolumeMapper a problem or not ?
> The HAVS volume mapper was really designed for unstructured grids.  I
> believe the test, for convenience, converts a structured grid to an
> unstructured grid.  But this conversion causes the number of cells to
> significantly and virtually guarantees that the rendering rate per
> will
> be slower.  Neither of things matter for a regression test, but they
> a
> big deal in practice.
> In practice, you would really only use the HAVS volume mapper in
> situations
> where you start with an unstructured grid.  In this case, the volume
> cast mapper is not really an option.
> -Ken
> > -----Original Message-----
> > From: vtkusers-bounces+kmorel=sandia.gov at vtk.org [mailto:vtkusers-
> > bounces+kmorel=sandia.gov at vtk.org] On Behalf Of
> the.answer3 at libertysurf.fr
> > Sent: Wednesday, July 18, 2007 6:46 AM
> > To: vtkusers
> > Subject: [vtkusers] vtkOpenGLHAVSVolumeMapper a problem or not ?
> >
> > Hi all,
> >
> > I tried to use the vtkOpenGLHAVSVolumeMapper to render a big vtk
> > (14 081 Ko). I watched the test TestHAVSVolumeMapper.cxx to see how
> > mapper works. So I used the same filters, etc... in my program than
> the
> > test.
> > Finally, I have bad results with this mapper since the result is
> > slower and less detailled than when I use vtkVolumeRayCastMapper. I
> > understand that the RayCast is more detailled but not faster than
> > HAVS.
> >
> > Here is the config of my working PC :
> > Intel Core 2 6600 - 2Go RAM - NVIDIA GeForce 8800 GTS
> >
> > That's why I wanted to use the GPU in order to accelerate the
> >
> > Does somebody have an idea on why I have so bad results ?
> >
> > Gourbish
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