[vtkusers] "Filling" parts of a volume that are "inside" a set of polyhedra

[Elvis Stansvik]

2017-07-24 5:30 GMT+02:00 Elvis Stansvik <elvis.stansvik at orexplore.com>:
> 2017-07-24 5:25 GMT+02:00 Dean Inglis <inglis.dl at gmail.com>:
>> good to know David, thanks!!!
>
> Many thanks to both of you. I had not found vtkPolyDataToImageStencil
> yet, but was looking more towards the concept of implicit functions.
> But this sounds like a much better approach, so I think I was right in
> reaching out :)

Just one thing I saw in the docs for vtkPolyDataToImageStencil now:

   "The polydata can either be a closed surface mesh or a series of
polyline contours (one contour per slice)."

Does this mean that, since I have a set of closed surfaces (upwards a
100 or so), I'd have to repeat the process David described, once for
each of my polyhedron? Or is there some way to generate a stencil from
many closed surfaces in one go?

Elvis

>
> Elvis
>
>>
>> - Dean
>>
>> On Sun, Jul 23, 2017 at 11:21 PM, David Gobbi <david.gobbi at gmail.com> wrote:
>>>
>>> Hi Elvis,
>>>
>>> I'd recommend generating a stencil with vtkPolyDataToImageStencil, then
>>> iterating over over all the voxels inside the stencil with
>>> vtkImagePointDataIterator:
>>>
>>> http://www.vtk.org/doc/nightly/html/classvtkPolyDataToImageStencil.html
>>> http://www.vtk.org/doc/nightly/html/classvtkImagePointDataIterator.html
>>>
>>> The iterator can efficiently give you the pointId for every voxel enclosed
>>> by the polyhedral surface (works for concave as well as convex surfaces).
>>> Once you have the pointId, you can set that voxel to whatever you want.
>>> There's a brief and vaguely relevant description on gitlab:
>>> https://gitlab.kitware.com/vtk/vtk/merge_requests/1118
>>>
>>>  - David
>>>
>>>
>>> On Sun, Jul 23, 2017 at 6:45 PM, Elvis Stansvik
>>> <elvis.stansvik at orexplore.com> wrote:
>>>>
>>>> Hi all,
>>>>
>>>> I have a set of points describing multiple convex polyhedra. The
>>>> polyhedra are for the most part disjoint in space, but they may
>>>> intersect slightly in some places.
>>>>
>>>> I need to create an empty voxel volume (all scalars 0), and then
>>>> "fill" the voxels that are inside one (or several) of the polyhedrons
>>>> with some Perlin noise. I also have access to normals for the faces
>>>> constituting the polyhedra, if necessary.
>>>>
>>>> Finally, I also have a single separate polyhedron (non-convex this
>>>> time), and as a finishing step, I'd like to fill the voxels that are
>>>> inside this polyhedron with a constant scalar value.
>>>>
>>>> Can VTK help me here?
>>>>
>>>> As this is new territory for me as far as VTK goes, any
>>>> pointers/advice on how to go about it would be much appreciated.
>>>>
>>>> Cheers,
>>>> Elvis
>>>
>>>
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>>