[vtk-developers] Discrete contouring classes

[Bill Lorensen]

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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