This is a Unity Native Plugin which wraps a subset of ACL. Its primary purpose is for use in DOTS-based projects.
Animation Compression Library, or ACL, is a C++11 library written by Nicholas Frechette and has been utilized in multiple AAA titles. It uses variable bit-rate compression of fixed-rate sampled poses for fast and highly accurate compression and decompression of both short and long clips. It is hierarchy-aware, further increasing its accuracy. It supports many platforms and can be compiled to utilize various levels of SIMD instructions.
Nicholas Frechette maintains an official Unreal Engine plugin. However, due to the closed-source nature of traditional Unity, he does not develop an equivalent for Unity.
This is an unofficial plugin for Unity primarily targeting DOTS-based projects. I (Dreaming381) wrote this wrapper for the needs of the Latios Framework. But feel free to use it or improve it as you see fit.
Traditionally, Unity uses curves for animation. It achieves performance by caching parts of the curve evaluation for use in the next evaluation. However, this approach doesn’t work as well in a DOTS project, where statelessness is preferred. ACL uses a technique that does not require caches to persist between frames in order to achieve great performance. It is also developed with a data-oriented mindset and API, making integration relatively straightforward.
If you are considering using this in your own DOTS-based animation solution,
consider storing compressed tracks in BlobArrays with forced 16-byte
alignment, and calling directly into this plugin from Burst jobs. You will also
want to borrow the ACL_Unity directory from the Latios Framework which contains
proper C# wrappers with safety checks.
Beginning with Latios framework 0.5.2, ACL Unity uses GitHub actions to generate build artifacts. These artifacts contain the binaries that were copied to the Latios Framework, as well as debug symbols and human-readable assembly text files.
The following platforms are supported out-of-the-box with binaries generated via GitHub Actions:
- Windows
- Mac OS (both x86 and ARM)
- Linux (x86 only)
- Android (ARM 32-bit and 64-bit)
Disclaimer: I am not very good with DevOps and am pretty happy I even got this project this far.
Adding support for a new platform should not require any C++ code changes. Instead, you will need to modify the top-level CMakeLists.txt to detect your target platform and specify the correct compiler flags for the different supported CPU architectures. The current CMakeLists.txt assumes your target platform is the same device that you are compiling for.
Once you have successfully compiled the library, import it into Unity as a native plugin. Depending on your target platform, you may need to modify the Kinemation/ACL_Unity C# files to load the correct version of the compiled library plugin for a given architecture. Note that when Burst is disabled, the code will always use the base version of the plugin with no extra CPU features.
Lastly, if your target platform is not constrained by NDA, you can support it in GitHub actions by modifying .github/workflows/acl-cross-platform-build.yml and adding a dedicated job with your platform. Every time you push changes, the jobs will run and you will be able to download and inspect artifacts. Test the artifacts to ensure they work correctly. Then create a pull request.
Fast!
And not like “fast enough for my personal use” fast.
More like “I doubt Unity’s engineers will ever beat this” fast.
Most animation sampling solutions (including Unity’s) require a keyframe search to find two keyframes the time value falls between. ACL doesn’t need to do this and instead looks up compressed byte offsets in a few instructions.
In addition, Burst support for native plugins is truly “native”. Performance of calling into this plugin from Burst jobs is on par with performance using ACL directly in C++ projects. Burst users get the full performance ACL has to offer.
So yeah. Fast!