[vtkusers] Requirements for multiple volumes in one render window

[Elvis Stansvik]

2016-02-29 16:32 GMT+01:00 Aashish Chaudhary <aashish.chaudhary at kitware.com>
:

> Hi Elvis,
>
> On Sat, Feb 27, 2016 at 12:06 PM, Elvis Stansvik
> <elvis.stansvik at orexplore.com> wrote:
> > 2016-02-25 17:10 GMT+01:00 Elvis Stansvik <elvis.stansvik at orexplore.com
> >:
> >>
> >> Hi,
> >>
> >> From searching around, I think I've gathered that to render multiple
> >> volumes in a single window, each volume must have its own mapper and
> volume
> >> property. They can't share mapper or property.
> >>
> >> My question is whether I must use separate renderers for each volume as
> >> well, or if I can use the same renderer for them all?
> >>
> >> Also, I did read something in an old post about problems with rendering
> >> multiple volumes that intersect (share a voxel). Is this still a
> problem?
> >> I'm using VTK 6.2 and the vtkVolumeRayCastMapper.
> >>
> >> Thanks in advance!
> >
> >
> > Including Donny's answer here, to keep the thread intact:
> >
> >> See this thread:
> >>
> >>
> >>
> http://vtk.1045678.n5.nabble.com/Rendering-multiple-volumes-td5734685.html#a5734971
> >
> > Thanks, that clears some things up, and brings up some workarounds. That
> > thread was from oct/nov last year, so I guess it is still the case that
> > proper rendering of multiple volumes that share voxels in 3D space is not
> > possible? (even with 7.0?).
>
> It depends what you define proper. If you have two volumes and they
> share the exact same space, you can combine them into one volume. When
> they share the same space but do not overlap that's when things get
> tricky since then the outcome depends on how do you want to handle
> this disparity. There could be some other ways such as you combine the
> volume into one. At the rendering level it could get tricky.
>
> What exactly you are trying to do.
>

I see, what I would expect I think is composite rendering of the voxels
using some composite rendering function / blending mode (perhaps
configurable?).

Sorry if my use case wasn't clear, I'm attaching a rough sketch I did just
now which should explain it better.

Each of our volumes is a piece of a drill core (see my photo previously in
this thread). The pieces were scanned stacked on top of each other in a
plastic tube inside our machine. During scanning, they are not necessarily
aligned properly (as shown in the sketch, and also in the photo).

We will do some algorithmic alignment of the volumes, but we must also
allow the user to override / supplement the automatic alignment when it
fails. This means the user should be able to rotate and move (along Z axis)
the pieces until they align. It's like a pussle with pieces of a drill core
:)

While the user is doing this, the volumes may intersect (noone is perfect
on the first try). This is why I'm asking about rendering multiple volumes
that partially intersect in 3D space.

It's very desirable that the user can see inside the volumes while doing
this manual alignment, since the features (cracks, density variations, ...)
inside the rocks may be what guides the user in aligning the pieces
properly. That's why I don't like the idea of letting the user work with
extracted isosurfaces or similar instead.

Hope this clears things up a little!

Elvis


> - Aashish
>
> >
> > Elvis
> >
> >>
> >> Elvis
> >
> >
> >
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>
> --
> | Aashish Chaudhary
> | Technical Leader
> | Kitware Inc.
> | http://www.kitware.com/company/team/chaudhary.html
>
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