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Filip Sivák

Modifying geometry of transforming primitives from Alembic

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Hello Everyone!

Let's have a pighead and animate it (rotation, scale or translation only, no deformation - this is important). Pack the primitive and store it as an Alembic with "Packed transform - Transform geometry". Then load the Alembic. My goal is to apply some deformation to the pighead - for example PolyReduce - after importing it from Alembic. However, this would apply PolyReduce to each frame separately and cost a lot of computational time. Even though the geometry is not changing from frame to frame, only it's transformation. Moreover, resulting Alembic would be "deforming" and not "transforming" anymore and the resulting file would be much bigger (1.4MB as opposed to the 200KB of original file).

How would you go about this?

Thank you!

 

AlembicTransforming.hip

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It's worth noting reading alembics in Sop's sets packed alembic pivot (the geometry point that represents the pivot) to the centroid of the pack I think. For this reason I prefer to use Houdini packed geo in these situations. 

You should be able to do your polyreduce and pack it (ensuring the pivot is correct), then use a wrangle to apply the packed primitive from the cached packed primitive transform intrinsic to the new packed primitive.

You may need some unique value attribute like "name", "id" or "path" to match the the undeformed and deformed packs together.

The same principle applies to Alembic prims, you'll just need account for for the pivot.

Hope this helps.

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Awesome! Glad you found the answer.

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