Production release of OpenVDB 7.2.0

[Ken Museth]

OpenVDB 7.2.0 is now available to download. The highlights of this release are:

• Faster CSG operations with new parallel breadth-first algorithms and tools
• Pre-release of AX, a JIT library for efficient manipulation of OpenVDB grids
  
• Added support for grids with matrix values
  
• Various bug fixes and other improvements

The complete release notes are included below for your convenience.

Version 7.2.0 - December 9, 2020

New features:

• Added DynamicNodeManager that lazily caches the nodes at each level of the tree to allow for efficient threading of topology-changing top-down workflows.
• Added CsgUnionOp, CsgIntersectionOp and CsgDifferenceOp that use a parallel breadth-first algorithm to accelerate CSG union, intersection and difference operations.
• Added TreeToMerge which provides methods to steal or deep-copy from a tree based on the tag dispatch class used in its construction.
• Pre-release of OpenVDB AX, an open source C++ library that provides a powerful and easy way of interacting with OpenVDB volume and point data.

Improvements:

• util::CpuTimer now uses C++11 chrono instead of TBB.
• Threaded the construction of LeafManager and NodeManager linear arrays.
• csgUnion, csgIntersection and csgDifference now use the new parallel breadth-first algorithms for much faster performance.
• Extended NodeManager to allow for use with a const tree.
• Added Abs, cwiseAdd, cwiseLessThan and cwiseGreaterThan methods for Matrix types. Matrix grids can now be instantiated.

Houdini:

• Fixed a bug in the OpenVDB Points Convert SOP where the auto voxel transform was ignoring the contents of packed geometry.
• Fixed a bug in the OpenVDB Points Convert SOP where points representing packed geometry were also being converted.
• Fixed a bug where a Houdini SOP's verb would not be correctly associated with the corresponding node if the node's internal name was changed.
• Fixed bug where OpenVDB Convert SOP could revert the name attribute.

Bug Fixes:

• Fixed a bug which could cause recursive compile time instantiations of TypeList objects, manifesting in longer compile times.
• Deprecated util::PagedArray::push_back due to a race condition. Instead use util::PagedArray::ValueBuffer::push_back which is faster and thread-safe.
• Fixed various cases of undefined behavior in some LevelSetUtil methods [Reported by fkemmler]

API changes:

• Deprecated tree::LeafManager::getNodes. This method is no longer used when constructing a NodeManager from a LeafManager.
• Deprecated Tree::visitActiveBBox, Tree::visit and Tree::visit2 methods in favor of using a tree::DynamicNodeManager.
• Removed tools::CsgVisitorBase, tools::CsgVisitorUnion, tools::CsgVisitorIntersection and tools::CsgVisitorDifference. The CSG tools now use the parallel breath-first algorithms.
• Moved openvdb::TypeList from Types.h into its own header TypeList.h

Build:

• Removed the Makefiles.
• Re-organised the repository layout such that each independent library is able to be configured against an existing installation of OpenVDB without ambiguous include paths.
• Upgraded CMake minimum version support to 3.12.
• Removed OPENVDB_STATIC_SPECIALIZATION macro which is no longer required.
• Fixed various compiler warnings for GCC 9.1.
• Moved to CMake doxygen commands and removed the doxygen-config files for doxygen documentation.
• Added USE_ZLIB compiler flag that enables zlib compression and defaults to on.
• Added the OPENVDB_STATICLIB define to all static builds to fix builds on Windows which use the multithread/DLL-specific version of the CRT. [Reported by Tobias Rittig]
• Core library unit tests use GoogleTest instead of CppUnit.