TSC Notes for Jan 17 2023

Signed-off-by: jlait <[email protected]>

Author: jmlait

tsc/meetings/2023-01-17.md

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+Minutes from 159th OpenVDB TSC meeting, January 17th, 2023
+
+Attendees: *Jeff* L., *Andre* P, *Dan* B., *Ken* M., *Nick* A., *Greg*
+H., *Rich* J.
+
+Additional Attendees: Peyton Murray
+
+Agenda:
+
+1) Confirm quorum
+2) Secretary
+3) Unitialized Point Flags in VolumeToMesh (PR1523)
+4) NanoVDB Static Asserts (PR1522)
+5) Hollow Mesh (PR1525)
+6) Next meeting
+
+------------
+
+1) Confirm quorum
+
+Quorum is present.
+
+2) Secretary
+
+Secretary is Jeff Lait.
+
+3) Forum
+
+There is one question about the sharp edges reconstruction that exists
+in Houdini but not the core library.  This has been discussed
+previously where we will be happy with someone porting the available
+code into the core library.
+
+4) Python Bindings
+
+Peyton added some automatons to cmake to support python.  But
+pyopenvdb exists, so we can't publish.  We need the owner's permission
+to take over, but have not been able to get consistent reply.   So
+perhaps we should publish as openvdb bindings on PyPi.  We have a PR
+to make all the python bindings pybind11.  Changing the name to
+openvdb seems totally fine.  Peyton will put it on hold until the
+pybind11 is done.  Renaming the module is most useful if we changed
+the API.  We could deprecate the old pyopenvdb vs openvdb?  Maybe
+pybind11 could publish to openvdb and old one publishes to pyopenvdb?
+
+Conclusion: pybind11 will publish to openvdb and we do not have to overtake
+the pyopenvdb package.
+
+Peyton will summarize this on the existing automation PR.
+
+5) Hollow VDB
+
+Discussion of the problem with dual contouring not matching the
+interpolation.  In magnification this can become quite severe so the
+oracle will set entire tiles to the wrong sign.  However,
+mangnification is also the case where there is little need for the
+dual contouring other than avoiding building a fat band.  The plan is
+to investigate resampling top-down a narrow band for the magnification
+case and see how well it works.
+
+This would be the rebuild changes behaviour depending on magnification
+vs minification.
+
+
+6) UUID Update
+
+Can the UUID in the file system be an arbitrary tag?  It is just a
+random string.   We can support blank strings to mean no uuid that
+always fails comparison checks.  std::random_device can throw so we
+need a sensible action in that case.
+
+Why do we have UUID in vdb tools?  It currently is only 32 bits of
+entropy, so has to be changed to cycle from std::random_device
+instead.
+
+7) ASWF Annual Meeting
+
+The meeting is on February 17th.  TSC updates are now optional.  We
+have to ask to present rather than mandatory presentation.  There are
+10, 20, and 40 minutes timeslots.  Do we have any updates?
+
+Conclusion: We will not have a presentation as our forward looking
+report hasn't changed overmuch.
+
+There is both a public part, and a governing board meeting that is
+closed.  The second half requires a set of bullet points.  
+
+Do we do a siggraph presentation?
+
+Bullet points are due January 19th.  We should point out that the paid
+runners in github actions made a big improvement for our last release.
+
+We can commit to making Boost optional.
+
+We can list as likely having pybind11, hollow VDB, half support, and
+vdb blend-fillet.
+
+We should consider a siggraph course this year.  Next meeting is to
+discuss farther.
+
+8) VDB Merge Max
+
+VDB Combine and Max produce different activation rules.   Inactive
+non-background values in particular are causing issues.  If an
+inactive voxel has the larger value, does it copy the inactivity?
+
+This seems to be something that should be an option?   Should inactive
+voxels contribute at all?
+
+Max seems it should be order independent with the inactivity copying,
+which seems contrary to the usual symmetry for Max.
+
+How do we expose an option?  Do we say Max with Active and Max
+without?  Maybe a transfer active state toggle?
+
+Unioning the two active states seems best? Or still needs to be an
+option?  Or do we just ignore inactive entirely? 
+
+What is should an empty grid with background value of ten which you
+max with a grid with topology with values less than ten result in?  Is
+it the same topology set to 10?  Or is it blown away empty grid with
+background value of 10?
+
+VDB Combine explicitly sets a union topology.  By definition, it
+unions topology and then applies the per-voxel operation.
+
+In general, we need a tool to set inactive values to background value.
+
+This ties back to inactive voxels containing non-background values.  A
+lot of tools just use inactive as mask.   And a lot of tools act as if
+inactive doesn't exist.
+
+So long as we document the choices we are okay with any particular
+answer to this.  Outside that is undefined behavior.  
+
+9) Next meeting
+
+Next meeting is on January 24th, 2023. 2pm-3pm EDT (GMT-4).