Fixed ellipsoid indexes

[ahcorde]

Fixed ellipsoid indexes, it was generating negative indexes.

Signed-off-by: ahcorde ahcorde@gmail.com

[codecov]

Codecov Report

Merging #159 (c63829f) into ign-common3 (a8e59e1) will not change coverage.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##           ign-common3     #159   +/-   ##
============================================
  Coverage        75.87%   75.87%           
============================================
  Files               69       69           
  Lines             9758     9758           
============================================
  Hits              7404     7404           
  Misses            2354     2354           

Impacted Files	Coverage Δ
graphics/src/MeshManager.cc	86.50% <100.00%> (ø)

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[nkoenig]

Is it possible to add a test?

[ahcorde]

@nkoenig added the test c63829f

I can add the same test for the rest of the meshes in other PR