Instance meshes where the "Data" mesh is reused between objects

[bsavery]

PURPOSE

Currently Objects which share a data mesh, we make a new mesh each time, this could be slow to export.

EFFECT OF CHANGE

With each mesh we check if it's unmodified and if the mesh is already exported to reuse and instance.

TECHNICAL STEPS

To do this we keep a dictionary of mesh masters

NOTES FOR REVIEWERS

TODO does not yet handle viewport updates.

[VascoPi]

The issue needs to be investigated, Q&A observed NorthStar crash of one of the test scenes. Narrowing down the issue:

• The issue occurs when the emission shader is assigned to the curve object type.
• It is reproduced using Blender >= 3.0.

[VascoPi]

The thing is that when during synchronization we convert the curve to the mesh Blender dynamically creates DepsgraphObjectInstance for that object. As result, we sync such objects twice. So in summary we have two objects in the render having only one real curve object in the scene.

related to Blender Release_Notes 3.0 Python_API section Geometry Instancing

[bsavery]

I guess I'm not clear where that code path would get used. Can you take a look @VascoPi

[VascoPi]

Fixed the crash and improved the instance's transform update. Waiting for autotest results.