[Octave-bug-tracker] [bug #55642] isosurface is slow

[Michael Leitner]

Follow-up Comment #1, bug #55642 (project octave):

Yes, it is embarrassing if the main problem is handled by an efficient
algorithm like marching cubes, and the post-processing is extremely
inefficient -- to give numbers, on my computer the four lines with n = 64 take
15 seconds, while adding "noshare" to the invocation of isosurface cuts this
down to 0.08 sec. 

Your idea is obviously correct. Below I attach a patch that incorporates this
idea. I also reworked the actual deletion of the vertices, which are now only
seven lines (excluding comments) and thus probably do not warrant an
outsourcing to __unite_shared_vertices__.m any more. 

The example runs now in 0.10 sec. This could perhaps be decreased still by
some 10 percent, along the lines of the FIXME in the code. But no need for
C++. 

(file #46178)
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Additional Item Attachment:

File name: patch                          Size:1 KB
    <https://savannah.gnu.org/file/patch?file_id=46178>



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