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derrick

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Resolved : [Alembic] How to know if an alembic was created with Maya or Houdini (in Python in Houdini) Oct. 15, 2018, 11:24 a.m.

The “abcecho” command line tool will report this information. There is currently no convenient way to access the information through the Alembic HOM extensions.

ROP Alembic Partition Mode does not work in 17 Oct. 12, 2018, 1:41 p.m.

The Partition Attribute is only meaningful if you export an Object hierarchy. When exporting from a SOP, the “Build Hierarchy From Attribute” option gives you greater control over where things should be placed in the resulting Alembic archive. Consider enabling “Build Hierarchy From Attribute” and creating a primitive string attribute (identified by the “Path Attribute” parameter) specifying where everything belongs in the resulting Alembic archive.

Trouble exporting alembic file Oct. 10, 2018, 2:28 p.m.

I see a few issues.

1) Alembic archives store data in a hierarchy. The Alembic ROP needs to express the data being exported as a hierarchy in the Alembic archive. In your example, the parameters on /obj/geo1/rop_alembic1 indicate the Alembic ROP should look for a primitive string attribute called “path” indicating where to place each shape in the hierarchy. However, if you look at the geometry fed into the Alembic ROP, there is no “path” attribute.

2) Shape nodes in an Alembic archive are things like polygons, curves, subdivision surfaces, etc. There cannot be a mix of subdivision surfaces and polygons in an Alembic shape node. If you want the inside to be a composed of subdivision surfaces and the exterior to be composed of polygons, the pieces need to be separated into multiple Alembic shape nodes.

3) Your geometry contains packed primitives. These contain both transform and shape data. You will want to tell the Alembic ROP how to export these two pieces of information. If you care about Alembic node names and keeping transform information separate from point positions, consider setting the “Packed Transform” parameter to “Merge With Parent Transform” and using the “path” attribute to specify where the shape node component should be placed in the Alembic hierarchy.

4) The Alembic ROP will export geometry attributes (used by materials) but does not support exporting materials (i.e. it will not generate material nodes in the Alembic archive).

Attached is a simple example of how to use the Alembic ROP.

The “abcecho” and “abcinfo” command line tools may be helpful if you are unsure about what actually was exported to the resulting Alembic archive.