Alembic Instancing

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Tyson Ibele

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Jan 15, 2022, 11:32:20 PM1/15/22

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Hi everyone,

I'm writing an Alembic exporter for various types of geometry. So far I have point clouds exporting fine, as well as combined meshes (lots of individual meshes combined together and sampled each frame)...what I can't find much information on is how to export instanced geometry. For example, I have a single non-deforming mesh, and 10000 transforms across which I want to instance the mesh. How should I setup my alembic file and data to support this instancing across industry-standard ABC importers?

Are there any code examples of how to do this out there? Or general guidance? Thanks in advance.

Lucas Miller

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Jan 19, 2022, 1:15:14 PM1/19/22

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Unfortunately not all of the DCCs will natively instance geometry, and each one has it's own nuances.

How big is the mesh you are instancing? If its very small, some DCCs might handle it better if you put the transformed data into one big shape.

Also since it's only one shape (instead of a larger hierarchy) it might be more efficient for some DCCs to just rely on the native Alembic data deduplication.

Here is how you can create an instance:

https://github.com/alembic/alembic/blob/master/lib/Alembic/Abc/OObject.h#L209

And the example tests which use it:

https://github.com/alembic/alembic/blob/master/lib/Alembic/Abc/Tests/InstanceTest.cpp