Fix setting normal map when not all submeshes have texcoords (ogre2)

[iche033]

🦟 Bug fix

Summary

Setting normal map to a a submesh could fail in ogre2 if the mesh contains other submeshes that do not have texture coordinates set. Ogre2 will fail to generate tangents (needed for normal maps) and throw an exception:

03:59:05: OGRE EXCEPTION(5:ItemIdentityException): Cannot locate an appropriate 2D texture coordinate set for all the vertex data in this mesh to create tangents from.  in Mesh::suggestTangentVectorBuildParams at ./OgreMain/src/OgreMesh.cpp (line 1913)

The fix is to generate texcoords for all submeshes when importing the common::SubMesh into ogre even if the common::SubMesh does not have any texcoords.

The alternative (ideal) fix is to update ogre to just skip generating tangents for those submeshes that do not have texcoords instead of throwing an exception.

Tested with the AnisotropyBarnLamp.glb model.

Before the fix, the whole metal part of the lamp mesh appears white. After the fix, the PBR textures are applied correctly:

The light bulb should be transparent so there's another bug somewhere else and that still needs to be fixed. For comparison, see the result rendered by threejs

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
• While waiting for a review on your PR, please help review another open pull request to support the maintainers

Note to maintainers: Remember to use Squash-Merge and edit the commit message to match the pull request summary while retaining Signed-off-by messages.

[ahcorde]

LGTM, just a minor comment about unsigned varirables

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.68%. Comparing base (0305b34) to head (4985dbe).

Additional details and impacted files

@@                Coverage Diff                @@
##           gz-rendering7     #976      +/-   ##
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+ Coverage          77.61%   77.68%   +0.06%     
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  Files                170      170              
  Lines              14726    14733       +7     
=================================================
+ Hits               11430    11445      +15     
+ Misses              3296     3288       -8     

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