[vtk-developers] Discrete contouring classes

[Bill Lorensen]

I brightened the edges rather than darkening them.
See
https://raw.githubusercontent.com/lorensen/SPLBrainAtlas/master/Models/Screenshot/white_matter_of_left_cerebral_hemisphere.png


On Sat, Dec 23, 2017 at 11:53 AM, Bill Lorensen <bill.lorensen at gmail.com> wrote:
> There are no normals in the cube files I generate. I do color the
> edges, so on large poly models, the dark edges may be causing the
> problem.
>
> For example, see this lower poly count model:
> https://raw.githubusercontent.com/lorensen/SPLBrainAtlas/master/Models/Screenshot/right_putamen.png
>
> On Sat, Dec 23, 2017 at 10:45 AM, Bill Lorensen <bill.lorensen at gmail.com> wrote:
>> I'll take a look to fix normals on cube models.
>>
>> On Sat, Dec 23, 2017 at 10:28 AM, Andras Lasso <lasso at queensu.ca> wrote:
>>> Hi Will and Bill,
>>>
>>>
>>>
>>> Surface generation from binary labelmap is an important task for us in 3D
>>> Slicer, to display segmentation results in 3D while it is being edited in
>>> 2D, We are very interested in any potential improvements.
>>>
>>>
>>>
>>> Currently, we use discrete marching cubes and sinc smoothing, which gives
>>> good results, but sometimes it can be quite slow (especially the smoothing
>>> step).
>>>
>>>
>>>
>>> We tried cube models but surface normals always pointed to x/y/z direction
>>> instead of actual surface normal direction, so it was very hard to see 3D
>>> shapes. This flat look is visible in your examples, too:
>>> https://raw.githubusercontent.com/lorensen/SPLBrainAtlas/master/Models/Screenshot/white_matter_of_left_cerebral_hemisphere.png.
>>>
>>>
>>>
>>> We use discrete marching cubes, but as far as I remember, we did not see
>>> huge differences between regular and discrete marching cubes. Is there a
>>> study or examples that compares them (visual appearance, accuracy,
>>> computation time, etc.)? Is there a solution that provides smooth surfaces
>>> (that would not require further smoothing step to remove staircase
>>> artifacts)?
>>>
>>>
>>>
>>> We also plan to evaluate how well we can visualize binary labelmaps in 3D
>>> using the new multi-volume-rendering feature that is being integrated into
>>> VTK now.
>>>
>>>
>>>
>>> Andras
>>>
>>>
>>>
>>> From: vtk-developers [mailto:vtk-developers-bounces at vtk.org] On Behalf Of
>>> Will Schroeder
>>> Sent: Saturday, December 23, 2017 8:35 AM
>>> To: vtk-developers <vtk-developers at vtk.org>
>>> Subject: Re: [vtk-developers] Discrete contouring classes
>>>
>>>
>>>
>>> FYI here is an example of discrete marching cubes at work. From Bill:
>>>
>>>
>>>
>>> Here is the SPLBrainAtlas;
>>> https://github.com/lorensen/SPLBrainAtlas/wiki/Atlas-Summary
>>>
>>> The two-paned images show Discrete on left, Cube's Model (also
>>> undersold) on right. STL files created using discrete followed by
>>> non-manifold joint smoothing.
>>>
>>>
>>>
>>> On Sat, Dec 23, 2017 at 8:30 AM, Will Schroeder <will.schroeder at kitware.com>
>>> wrote:
>>>
>>> FYI- Back in the day (2004) Jim Miller and Bill Lorensen added the
>>> vtkDiscreteMarchingCubes class. This is used to generate contours for label
>>> masks (as you would find in segmentation). The key here is that the labels
>>> are non-continuous (i.e., scalar field is not smooth) so the regular edge
>>> interpolation of something like marching cubes doesn't work. Long story
>>> short, this class interpolates on the mid-edge point between regions, and it
>>> generates different regions (i.e., meshes) for each label.
>>>
>>>
>>>
>>> This class and approach is woefully underappreciated and underused.
>>>
>>>
>>>
>>> I am just adding flying edges versions (2D and 3D) of this functionality (MR
>>> 3739). These are of course much faster and scalable across multiple cores.
>>> They also produce slightly different results. Principally they do not merge
>>> coincident points belonging to different regions (since flying edges does
>>> not use a point locator) -- this is both good and bad depending on the
>>> application. Also normals are generated by the flying edges algorithm, not
>>> by vtkDiscreteMarchingCubes.
>>>
>>>
>>>
>>> See the docs for more info.
>>>
>>>
>>>
>>> Best,
>>>
>>> W
>>>
>>>
>>>
>>> --
>>>
>>> William J. Schroeder, PhD
>>> Kitware, Inc. - Building the World's Technical Computing Software
>>> 28 Corporate Drive
>>> Clifton Park, NY 12065
>>> will.schroeder at kitware.com
>>> http://www.kitware.com
>>> (518) 881-4902
>>>
>>>
>>>
>>>
>>>
>>> --
>>>
>>> William J. Schroeder, PhD
>>> Kitware, Inc. - Building the World's Technical Computing Software
>>> 28 Corporate Drive
>>> Clifton Park, NY 12065
>>> will.schroeder at kitware.com
>>> http://www.kitware.com
>>> (518) 881-4902
>>>
>>>
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>>
>>
>>
>> --
>> Unpaid intern in BillsBasement at noware dot com
>
>
>
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