[vtkusers] volume rendering content does not fit into the isosurface

[Lisa Avila]

vtkImageData has an Origin, which is used by the volume mappers to 
correctly place the volume in 3D space. It is also used by the contour 
filter to produce correct 3D vertices for the triangles. These should match 
up. If they do not, then the origin / extent  for the data you are passing 
into the contour filter does not match the origin / extent  of the data 
going into the volume mapper (or there is a bug - but intermixed 
isosurfaces / volume rendering is something that is tested nightly....)

Lisa


At 01:48 AM 9/6/2005, Peter wrote:
>vtkExtractVOI gives different results on vtkContourFilter and 
>vtkVolumeRayCastMapper.
>especially the SetVOI
>
>SetVOI carries arguments in a manner as below:
>
>SetVOI a b c d e f ( a...f  = integer)
>
>the "a" actually affect the output.
>
>in vtkContourFilter, when the part was "cut" off, the postion of the 
>cut-off part will be reserve
>
>however in vtkVolumeRayCastMapper, it does not reserve the space of the 
>cut-off part, and pushes the whole object to left (simply because the left 
>cut-off part is no more there )
>
>so it make the volumn rendering content can not "register" with 
>iso-surface rendering. i know the cause of the problem, but i haven't find 
>the solution yet.... maybe there are some other implementation on this....
>
>thank you for your advice.
>
>regards
>
>Yours
>Pan
>
>
>On 9/6/05, Day, Robert 
><<mailto:Robert.Day at health.wa.gov.au>Robert.Day at health.wa.gov.au> wrote:
>Its only a guess, based on looking at the picture and no code, and I don't 
>use volumes much.
>
>I'd say the origin for the volume data set is not the same as the 
>surface.  As I recall, volumes have the origin at one corner, whereas the 
>CT may well have the origin at the isocentre of the scanner.  So the 
>surface polydata will inherit this origin, but the volume may well have 
>its origin at the corner.
>
>It would be easier to guess with some code...
>
>Rob.
>--
>Robert Day            ph  +61 8 9224 3227
>Project Bioengineer   fax +61 8 9224 1138
>Royal Perth Hospital  <mailto:robert.day at health.wa.gov.au> 
>robert.day at health.wa.gov.au
>
> > -----Original Message-----
> > From: Peter [mailto:meancity at gmail.com]
> > Sent: Saturday, 27 August 2005 2:19 PM
> > To: <mailto:vtkusers at vtk.org>vtkusers at vtk.org
> > Subject: [vtkusers] volume rendering content does not fit into the
> > isosurface
> >
> >
> > Dear All,
> >
> > i have a question, i am doing some rending for a 3D object.
> >
> > first i did isosurface rendering for the objects.
> > then i did volume rendering.
> >
> > these two rending process in same file, but when i run the script,
> > the volume rendering content does not fit into the isosurface, i tried
> > to find the problem, but i still can't figure it out by far. i suppose
> > the volume rendering content should exactly fit into the isosurface.
> > but the result showed that there are just some part of
> > overlapping.....
> >
> > so can someone out there to help me out on this issue...
> >
> > thank you in advance,
> >
> > Yours
> > Pan
><snip>
>
>
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