[Insight-users] Few questions about quad edge mesh filters

[Andriy Fedorov]

On Wed, Mar 17, 2010 at 12:07, Andriy Fedorov <fedorov at bwh.harvard.edu> wrote:
> 1) the normals produced by QuadEdgeMesh are always (nan,nan,nan). I
> saw the comment in the documentation, that the input and output mesh
> traits should be the same for this filter to work, but this does not
> seem to help.
>

Update: this happens with the default (THURMER) weight type for
normals calculation, because the weight is calculated to NaN. If I
switch to GOURAUD or AREA weights, it seems to work.

By the way, the documentation does not mention what is the difference
between the different normal calculation modes. Is there an Insight
Journal paper that lists the details?


> 2) whenever I am using QuadEdgeMeshQuadricDecimation, the decimated
> surface is obviously incorrect
> (QuadEdgeMeshSquaredEdgeLengthDecimation generates very nice surface).
> Attached are screenshots for the MC surface, quadrics-decimated
> surface, and squared edge decimation result
>
> Source code and test data: http://dl.dropbox.com/u/3770904/QuadEdgeTests.tgz
> Command line to reproduce the first problem (second issue can be
> reproduced trivially by swapping the decimator): "QuadEdgeMeshTests
> blob1.nrrd output_mesh.vtk 10"
>
> I see this problem both with the latest checkout of the 3.16 branch,
> and with the current trunk build.
>
> Am I doing something wrong, or is this a bug?
>
> Thanks
>
> Andriy Fedorov
>