5.5 KiB
Minutes from 87th OpenVDB TSC meeting, April 20th, 2021, (EDT)
Attendees: Nick A., Jeff L., Ken M., Dan B, Andre P.
Additional Attendees: JT Nelson (Blender), Bruce Chernaik (Intel), Roman Zulak (ImageWorks), Johannes Meng (Intel), Sergio Rojas
Regrets: none
Agenda:
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Confirm Quorum
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Secretary
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Forum
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Website
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Cebas reporting issue freeing grids
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Status on OpenEXR dependency
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Screen sharing
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AX Update
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InternalNode ValueOff iterator
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String Grids
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VDB Viewer
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PR1010 - Active Voxel Count PR
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PR1024 - DynamicNodeManager Grain Size PR
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PR1033 - Fix to VDB Rebuild SDF SOP PR
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PR1031 - VDB Merge SOP PR
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Mantra Rendering Performance - VDB vs Houdini Volume
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Blind Data
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TBB 2021 update
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Houdini Transforms
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TypedAttributeArray ptr to buffer
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Next Meeting
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Confirm Quorum
Quorum is present.
- Secretary
Secretary is Nick Avramoussis
- Forum
Discussion around the google forum which can no longer be embedded into the website. Github discussion seems like a good replacement. We could make the google forum read only and/or remove the link from the openvdb forum website and instead point to the github discussions page. We should vet github discussions before transitioning. Dan to enable discussions on the website repo for us to test.
- Website
Ken has updated the website with new images from ILM.
- Cebas reporting issue freeing grids
A client is observing a significant performance slowdown running rasterization code thousands of times, specifically on Windows. There is no IO involved. This sounds like an allocator or threading issue. Ken to feedback and suggest trying tbbmalloc if they are not already.
Related google forum post: https://groups.google.com/g/openvdb-forum/c/MQZOpQ3h5lM/m/BKhEG75yBAAJ
- Status on OpenEXR dependency
This has been merged into master but not yet released. Ken has run into issues building OpenVDB and believes they are related to this. Ken to investigate further and feedback.
- Screen sharing
Tested, only Ken (the host) is able to screen share. Nick to contact John for assistance.
- AX Update
Major update to AX coming which introduces active tile streaming and significant performance enhancements for Volume kernels due to better vectorization. The following 3 topics were encountered from this work.
- InternalNode ValueOff iterator
Nick, this iterator runs of child nodes. The ValueOff iterators on the grid, tree and leaf node, do not. Nick, caught out unexpectedly by this behaviour, is there any way this could be changed? Probably not directly. Ken, you can create a mask that represents these values but, if you're using a non-const iterator, how do you then change these values if you write to them. Best solution would be to make the documentation more clear (but it is difficult) as people already expect this API to exists in the same way across all VDB nodes.
- String Grids
Nick, AX works with string grids but, during unit testing, found that vdb_print crashes when trying to read one in. There are no tests for string grids in VDB but they are a supported type by the serializer. All agreed we should deprecate the typedef whilst retaining support and see if anyone gets in touch with concerns.
- VDB Viewer
Nick, discussions with JT about ways to introduce people to AX. An interactive viewer is needed which at the moment means users have to install Houdini. The vdb viewer is in a bit of a weird state. It lives in the main repo but is only used by the vdb view binary. It advertises an API but has no tests and is not installed. NanoVDB contains a new viewer which is far superior but more complex to build. All agree a simple, basic viewer makes sense to exist alongside a more feature full application. Agreement that the viewer directory should not be advertised as an API and be moved to live alongside the vdb_view binary. For AX, we should wait for the more complicated viewer which will support the features AX needs. Nick to address the vdb_view library.
- PR1010 - Active Voxel Count PR
Dan, feedback regarding API stability has been implemented now. Ken to review with a deadline to merge next week.
- PR1024 - DynamicNodeManager Grain Size PR
Dan, PR exposes 2 grain sizes for leaf nodes and tiles. It's hard to automate these values and makes defaults difficult to specify. Jeff, part of the problem is the structure of the VDB tree resulting in 8 root child nodes when data is created with each sign flip. Jeff, we should investigate changing this for VDB 9 and change where we centre grids. TSC to review the PR.
- PR1033 - Fix to VDB Rebuild SDF SOP PR
Dan, "bugfix" due to the nature of the rebuild operation which doesn't fall into the category of producing a "new" grid (in-place op). The grid's metadata is dropped and shouldn't be. This PR addresses the issue specifically in Houdini. Nick approved, Jeff to review.
- PR1031 - VDB Merge SOP PR
Dan, new merge functionality targeted for 8.1 is up. New Merge Houdini SOP and sum operator. To be reviewed by TSC.
- Mantra Rendering Performance - VDB vs Houdini Volume
Dan, converting to Houdini volumes seems to result in better rendering performance. Dan, to collect some more examples so we can examine the differences.
- Blind Data
Dan, proposal to add a 32bit int to the leaf nodes which shouldn't change their size on 64bit architecture. Jeff, should this data be saved or copied? Dan, purely transient data which is never serialized. Designed to target individual algorithms.
18-20) Time
- Next Meeting
Next meeting is April 27th, 2021. 12pm-1pm EST (GMT-5).