[vtkusers] Re: Opacity problems with vtkVolume

[Dennis Jen]

When I set all opacity points to 0.0, nothing changes at all.  I kind of
gave up getting opacity to work this way.  Instead, I'm using the
SetOpacity function, i.e. actor.SetOpacity(some_number).  For my
isosurface, this seems to work, although I would have liked to get it
working for my volumes (maximum intensity projection.).
 
-----Original Message-----
From: vtkusers-admin at vtk.org [mailto:vtkusers-admin at vtk.org] On Behalf
Of anast.jm at pg.com
Sent: Thursday, June 19, 2003 5:17 PM
To: vtkusers at public.kitware.com
Subject: [vtkusers] Re: Opacity problems with vtkVolume
 

Sorry for the resend....realized the subject line wasn't too descriptive
in the original post...john 

----- Forwarded by John Anast on 06/19/2003 05:15 PM ----- 

I'm on WinXP with vtk 4.2 from a recent CVS build. I'm not seeing this
problem. I have a small tcl script that compares side by side the
RayCast Mapper and VolumePro mapper on the poship volume dataset and the
opacity it behaving properly for both mappers. What does your volume
look like after setting all opacity points to 0.0?? ...john 




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"Nico Vermaas" <vermaas at astron.nl> 
Sent by: vtkusers-admin at www.vtk.org 
06/19/2003 02:28 AM 
        
        To:        <vtkusers at public.kitware.com> 
        cc:        <dsjen at cs.unc.edu>, (bcc: John Anast-JM/PGI) 
        Subject:        [vtkusers] Re: vtkusers digest, Vol 1 #1884 - 11
msgs



Hi Dennis,

I have exactly the same problem with 4.x on Linux (Suse 7.3), if you
find a solution let me know. Will do the same.

Nico
----------------------------------------------------------------
Message: 4
From: <dsjen at cs.unc.edu>
To: vtkusers at public.kitware.com 
Date: Fri, 13 Jun 2003 13:20:01 -0400
Subject: [vtkusers] Volume Opacity

Hello VTK Users,

I'm having trouble changing the opacity of a vtkVolume.  I'm creating 
a vtkPiecewiseFunction and adding the following points to the function 
with the following lines of code, where opacity is a the piecewise 
function:

                opacity.AddPoint(0, 0.0);
                opacity.AddPoint(255,0.0);

This should make the volume completely transparent after I set the 
opacity of the volume:

                ...
                ...
                property.SetScalarOpacity(opacity);
                ...
                ...
                actor.SetProperty(property);
                ...
                ...

If anyone has any suggestions, needs clarification, or can point me to 
any references, I'd be very grateful.  Also, just for reference, I'm 
using vtk4.0 on WindowsXP.

Thanks,
Dennis



====================================================
Nico Vermaas
ASTRON - Westerbork Synthesis Radio Telescope
Schattenberg 1 - 9433 TA Zwiggelte - The Netherlands

tel: +31 593 598710                 
vermaas at astron.nl 
====================================================


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