Add meeting notes

Signed-off-by: Dan Bailey <danbailey@ilm.com>

Author: danrbailey

tsc/meetings/2023-12-19.md

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+Minutes from OpenVDB TSC meeting, December 19th, 2023
+
+Attendees: *Jeff* L., *Andre* P, *Dan* B., *Ken* M.
+
+Additional Attendees: 
+
+Regrets: *Nick* A., *Rich* J.
+
+Agenda:
+
+1) Confirm quorum
+2) Secretary
+3) Autodesk VTT
+4) Read-Only Grids
+5) Half Grid Types
+6) Next meeting
+
+------------
+
+1) Confirm quorum
+
+Quorum is present.
+
+2) Secretary
+
+Secretary is Dan Bailey.
+
+3) Autodesk VTT
+
+Potential 9th January meeting to discuss VTT responses with Autodesk. To be
+proposed.
+
+NanoVTT is being pitched for integration now, VTT for later. VTT is not being
+proposed or considered as a replacement for VDB, will be complementary.
+
+One of the key questions is around GridBase/TreeBase integration. Autodesk
+suggests TreeBase will be easier, but it is thought there may have been some
+confusion there as GridBase is many fewer methods. Curious to understand the
+concern better. The Autodesk response appears to rely on expectation that
+integrating greater functionality to the tree/grid classes is desired by TSC,
+however worth sharing back that efforts have been underway for years to extract
+functionality from the object-oriented hierarchy classes and to move more
+towards using free-standing tools. Perhaps a better candidate would be to start
+from NanoVTT and work towards making that a canidate for VTT.
+
+Autodesk not opposed to the idea about using VDB transforms. Question over
+transforms leads to the assumption that VTT does have transforms but that it
+exists at a higher-level than VTT in the BiFrost API. Would be good to confirm
+this.
+
+Would like to propose an MVP for VTT in addition to considering NanoVTT.
+Candidates are conversion (VDB <-> VTT), serialization, sampling and
+re-grading.
+
+Reflecting on NanoVDB experience, one learning is that NanoVDB grids were
+originally pitched as read-only, however subsequent realization was that
+obtaining the memory layout would allow room for modifying the grid values.
+GridHandle is one of the more awkward components of NanoVDB that is simpler in
+OpenVDB.
+
+While three of the MVP requirements appear to suggest an ability to pre-allocate
+memory, grading is expected to require dynamic memory management in VTT.
+
+4) Read-Only Grids
+
+Question over whether there is value in having a VDB grid that uses contiguous
+memory to accelerate performance. Even with an allocator like jemalloc, the
+smaller fragments of memory in VDB are a considerable source of slowness.
+NanoVDB is a grid with a contiguous block of memory and exists on the host as
+well as the device. Limitation is that you cannot deserialize vdb files
+directly into NanoVDB grids, you have to go via VDB or use nvdb files.
+
+5) Half Grid Types
+
+Brief discussion of Andre's work adding half grid support. Looking very
+promising. Main component missing is VDB I/O which should be alleviated by
+registering the VDB half grid type. Worth also adding static asserts to disable
+tools that either do not support half grid types or have not yet been tested.
+
+Subsequent discussion around extending the std namespace being UB. Ken points
+out that this is already done in the math/Coord around hash usage, this should
+be resolved. The approach being taken in this PR is the right approach by using
+openvdb::is_floating_point. Will also be needed in the pybind11 functionality
+that Matt Cong is working on due to needing to specialize std::is_arithmetic.
+
+6) Next meeting
+
+Next meeting is on January 9th, 2024. Intention is to invite Autodesk. 2pm-3pm
+EDT (GMT-4).