Holes in trimmed NURBS surface lost after AbcExport/AbcImport

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What steps will reproduce the problem?
1. Open the attached scene. (Simply a trimmed NURBS surface with a hole)
2. AbcExport
3. AbcImport

What is the expected output? What do you see instead?
Expected: The hole should be preserved after export/import.
Actually: The hole is lost.

What version of the product are you using? On what operating system?
Alembic 1.0.3 on all platforms.

Please provide any additional information below.

Maya's trimmed NURBS: region -> boundaries -> curve group
A trimmed NURBS has several regions. In each region, there are 1 outer boundary 
and optional inner boundaries. Each boundary consists of several curves that 
form a closed loop.

Alembic's trimmed NURBS: loop -> curve group
I think Alembic has the same semantic with RenderMan.
RenderMan's doc says: "The curves of a loop connect in head-to-tail fashion and 
must be explicitly closed."
(http://graphics.stanford.edu/lab/soft/purgatory/prman/RISpec/section5.html#RiTr
imCurve)

So I think a Maya boundary is equivalent to a RenerMan's loop.
AbcExport treats a region as a loop. This causes the problem.

Original issue reported on code.google.com by shinc...@gmail.com on 24 Nov 2011 at 11:48

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Attch the scene.

Original comment by shinc...@gmail.com on 24 Nov 2011 at 11:55

Attachments:

• trim.ma

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Original comment by miller.lucas on 9 Dec 2011 at 5:21

• Added labels: Component-Maya_Import

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I think this change will fix your issue:

http://code.google.com/r/millerlucas-dev/source/detail?r=fc1c3e1342c1e9aecb5ac10
226523afafd950bc2

Original comment by miller.lucas on 17 Jan 2012 at 6:49

• Changed state: PleaseVerify

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Original comment by miller.lucas on 24 Jan 2012 at 1:41

• Changed state: Verified