UV data type and UV Set name problems in Houdini

I have to say, this is one of the strangest parts of Houdini:
Handling UVs and UV sets (in Maya term).

Sometimes you have to deal with external alembic files in Houdini.
That abc file could contain “not ideal” kind of UV data which is problematic to handle.
In those cases, Houdini tries its best to convert the data so it can be used correctly, but that means it will change the data type and also rename the UV Set automatically to uv.
Unfortunately, that data type conversion and the renaming part is not optional.


The arrow is the indicator of the data type change in the Vertex Attrs line.

At the end of the process, you always get back (at the export, using ROP Alembic) the original UV Set names. But that is not a variable or an attribute to change (not always a good thing).

You need a little trick as a workaround to solve the issue:

  1. Use an Unpack node after the Alembic node to make all data available.
  2. Add an Attribute VOP node
    • Inside that, use a Bind node to load all uv data into a uv2 named attribute
      (Connect the uv to the Bind node)
  3. Add an Attribute Delete node and delete the original uv vertex attribute
  4. Use an Attribute Rename node to rename uv2 to uv
    Go to the Vertex tab
  5. Add an Attribute Wrangle node to set the uv data type
    The Group Type and Run Over are set to Vertecies
    setattribtypeinfo(0, "vertex", "uv", "texturecoord");

That’s it.

Aftar that you can use with the exported geometry in any software correctly (including Maya).

Cheers, D

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