Volume rendering prob

[Elizabeth Bullitt]

Hi Lisa--
	Your response was right on the money.
	The voxel size was (0.06, 0.06, 0.1) and I was using the default
RayCastMapper stepsize, so most of the rays just "jumped over" anything
of interest. Also explains why things worked fine with voxel size of
(1,1,1). The problem's fixed now.
	My genuine thanks for your time.
Liz
--------------------------------------------

"Lisa S. Avila" wrote:
> 
> Hello Liz,
> 
> How big are xstep, ystep and zstep? What volume mapper are you using? This
> should work fine with either the vtkVolumeTextureMapper2D or the
> vtkVolumeRayCastMapper if you don't have overlapping volumes, and if the
> surface rendering contains only opaque geometry. For multiple texture
> mapped volumes, you will have to turn back-to-front sorting on in the
> culler for the volumes to be rendered in the correct order. Keep in mind
> that if any of your spacing values are much smaller than 1.0, then you will
> likely need to decrease your sample distance in the ray cast mapper in
> order to correctly sample the volume along the ray.
> 
> Hmmm, reading your email more closely I have the following question - how
> many components in your input data set? The volume rendering mappers
> currently can only handle 1 component unsigned char or unsigned short
> structured points data sets.
> 
> If you could reproduce the problem in a tcl script or small piece of C++
> code with one of the distributed data sets (like poship.slc) that would
> really help.
> 
> Lisa
> 
> At 12:33 AM 11/30/99 -0800, Elizabeth Bullitt wrote:
> >Could anyone provide insight into the following problem?
> >
> >I would like to combine perspective surface rendering of various objects
> >with perspective volume rendering of other objects. The input data for
> >the volume rendering is a structured point dataset with associated
> >scalar color data, and with axially unequal, floating point spacings of
> >[xstep, ystep, zstep].
> >       All objects, whether surface or volume rendered, are positioned within
> >a global coordinate system via SetUserMatrix().
> >
> >       I have had not had any problem with surface rendered objects. The
> >problem is with selective volume rendering within the same global
> >coordinate space.
> >
> >       I can get the CONFINES of a requested volume rendered region to display
> >correctly under various rotations/translations relative to surface
> >rendered data, using SetSpacing(xstep, ystep, zstep) to help define the
> >structured points volume. The CONTENTS of the supposedly volume-rendered
> >volume is, however, bad and often blank.
> >       Under a test program, I can get the contents of an individual
> >volume-rendered region to display correctly both initially and under
> >various rotations/translations only if I finally rescale the final
> >volume by (1/xstep, 1/ystep, 1/zstep). This makes the contents correct,
> >but the CONFINES of the the volume rendered region incorrect relative to
> >other objects within a world coordinate system.
> >
> >       Suggestions would be genuinely appreciated.
> >Liz
> >
> >
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