OpenSubdiv Petite

A selective Rust wrapper for Pixar’s OpenSubdiv library.

Versions

For now crate versions reflect code maturity on the Rust side. They are not in any way related to the OpenSubdiv version that is wrapped.

• v0.1.x – OpenSubdiv v3.4.4

Features

There are several features to gate the resp. build flags when OpenSubdiv is built.

Almost all of them are not yet implemented.

• clew – TBD. Adds support for CLEW.
• cuda – Adds support for the Nvidia CUDA backend. Only valid on Linux/Windows. CUDA support is almost done (Rust API wrappers are there). It just require some more work in build.rs. Ideally, if the cuda feature flag is present, build.rs would detect a CUDA installation on Linux/Windows and configure the OpenSubdiv build resp. panic if no installation can be found.
• TBD. metal – Adds support for the Apple Metal backend. Only valid on macOS.
• opencl – TBD. Adds support for the OpenCL backend.
• ptex – TBD. Adds support for PTex.
• topology_validation – Do (expensive) validation of topology. This checks index bounds on the Rust side and activates a bunch of topology checks on the FFI side. This is on by default! Set default-features = false in Cargo.toml to switch this off – suggested for release builds.

OpenMP Support on macOS

OpenMP detection is broken on the CMake side on macOS. There are a bunch of issues open in the CMake tracker. I added some comments here.

A workaround is likely possible. PRs welcome. If you need to make a fix on the OpenSubdiv side, Pixar will probably also welcome a PR.

Limitations

The original library does make use of C++ templates in quite a few places. The wrapper has specializations that cover the most common use cases.

C++ factory classes have been collapsed into the new() method of the resp. struct that mirrors the class the C++ factory was building.

API Changes From C++

Many methods have slightly different names on the Rust side.

Renaming was done considering these constraints:

• Be verbose consistently (the original API is quite verbose but does make use of abbreviations in some suprising places).
• Use canonical Rust naming – (num_vertices() becomes vertices_len()).
• Use canonical Rust constructs. Most option/configuraion structs use the init struct pattern. In places where it’s not possible to easily map to a Rust struct, the builder pattern (or anti-pattern, depending whom you ask) is used.
• Be brief when possible. Example: StencilTable::numStencils() in C++ becomes StencilTable::len() in Rust.
• Use unsigned integer types, specifically usize and u32, instead of signed ones (i32) for anything that can only contain positive values (indices, sizes/lengths/counts, valences, arities, etc.). Types should express intent. See also here.