facebookresearch/momentum
Oct 2024 – Oct 2025
13 Months active
Languages Used
C++PythonBzlEigenJSONCMakeSQLStarlark
Technical Skills
C++Linear AlgebraPythonQuaternion MathSoftware EngineeringBuild Systems
Chris Twigg
PROFILE
Chris Twigg
Chris Twigg developed core animation, geometry, and optimization features for the facebookresearch/momentum repository, focusing on robust asset pipelines and high-performance character workflows. He engineered systems for skeletal animation, mesh processing, and constraint-based solvers, leveraging C++, Python, and pybind11 to bridge efficient backend logic with flexible Python APIs. His work included SIMD-optimized collision detection, GLTF asset integration, and differentiable IK solvers, all designed for maintainability and extensibility. By refactoring core modules, improving documentation, and automating error function generation, Chris enabled reliable, scalable pipelines for 3D character assets. The depth of his contributions reflects strong architectural and cross-language engineering skills.
Overall Statistics
Feature vs Bugs
81%Features
Repository Contributions
160Total
Bugs
16
Commits
160
Features
70
Lines of code
46,580
Activity Months13
Your Network
2284 people
Work History
October 2025
23 Commits • 11 Features
Oct 1, 2025October 2025 momentum repository delivered a set of performance improvements, feature expansions, and developer ergonomics enhancements across rendering, physics/collision, and tooling. Key outcomes include faster rendering and collision checks via SIMD optimizations, deeper Momentum integration with Python bindings, a robust SDF-based collision pipeline, and enhanced mesh handling enabling smaller assets and faster iteration. A regression fix for skinweights was completed and Python bindings/documentation efforts were advanced to improve adoption and scripting flexibility.
23 Commits • 11 Features
Oct 1, 2025October 2025 momentum repository delivered a set of performance improvements, feature expansions, and developer ergonomics enhancements across rendering, physics/collision, and tooling. Key outcomes include faster rendering and collision checks via SIMD optimizations, deeper Momentum integration with Python bindings, a robust SDF-based collision pipeline, and enhanced mesh handling enabling smaller assets and faster iteration. A regression fix for skinweights was completed and Python bindings/documentation efforts were advanced to improve adoption and scripting flexibility.
October 2025
September 2025
36 Commits • 13 Features
Sep 1, 2025Month 2025-09 (facebookresearch/momentum) — Delivered a broad set of features, API improvements, and targeted bug fixes across the Momentum project with clear business value: improved documentation, enhanced Mocap and PyTorch support, streamlined GLTF data handling, and robust Skeleton State functionality.
September 2025
36 Commits • 13 Features
Sep 1, 2025Month 2025-09 (facebookresearch/momentum) — Delivered a broad set of features, API improvements, and targeted bug fixes across the Momentum project with clear business value: improved documentation, enhanced Mocap and PyTorch support, streamlined GLTF data handling, and robust Skeleton State functionality.
August 2025
16 Commits • 6 Features
Aug 1, 2025August 2025 delivered a focused set of features and stability improvements in facebookresearch/momentum that advance asset compatibility, runtime reliability, and developer productivity. Key outcomes include: - Legacy JSON data support and Python bindings to convert legacy skeletons, skinned models, collision geometry, and locators to the current Momentum format, enabling legacy data migration and continuity of pipelines. - Skinned Locator system and solver with multi-bone locators, skinning-transforms-based positioning, triangle-offset constraints, and Python bindings, providing accurate locator placement and easier experimentation. - Vertex velocity constraints and solver robustness with VertexSequenceErrorFunction, Python bindings, and non-negative solver weights to improve convergence and stability under dynamic conditions. - Locator conversion to skinned locators via mesh proximity, automating conversion and weight interpolation when within a defined distance for smoother migrations. - Character.clone() support in pymomentum, enabling deep copies of Character objects to prevent unintended nonlocal modifications. In addition, debugging and representation improvements for marker_tracking and locator/skinned locator objects, plus targeted blend shape and skinning cleanup, reduce maintenance burden and edge-case regressions. Overall impact: faster onboarding of legacy assets, more reliable character localization pipelines, and a stronger foundation for tooling and experimentation via Python bindings.
16 Commits • 6 Features
Aug 1, 2025August 2025 delivered a focused set of features and stability improvements in facebookresearch/momentum that advance asset compatibility, runtime reliability, and developer productivity. Key outcomes include: - Legacy JSON data support and Python bindings to convert legacy skeletons, skinned models, collision geometry, and locators to the current Momentum format, enabling legacy data migration and continuity of pipelines. - Skinned Locator system and solver with multi-bone locators, skinning-transforms-based positioning, triangle-offset constraints, and Python bindings, providing accurate locator placement and easier experimentation. - Vertex velocity constraints and solver robustness with VertexSequenceErrorFunction, Python bindings, and non-negative solver weights to improve convergence and stability under dynamic conditions. - Locator conversion to skinned locators via mesh proximity, automating conversion and weight interpolation when within a defined distance for smoother migrations. - Character.clone() support in pymomentum, enabling deep copies of Character objects to prevent unintended nonlocal modifications. In addition, debugging and representation improvements for marker_tracking and locator/skinned locator objects, plus targeted blend shape and skinning cleanup, reduce maintenance burden and edge-case regressions. Overall impact: faster onboarding of legacy assets, more reliable character localization pipelines, and a stronger foundation for tooling and experimentation via Python bindings.
August 2025
July 2025
24 Commits • 6 Features
Jul 1, 2025Summary for 2025-07: Key features delivered: - Error Function API and Representation improvements for momentum: added offset support for sequence_state_error_function, bindings for VertexProjectionErrorFunction, and __repr__ implementations for error functions. - Solver core improvements and validations: introduced solver parameter enabling, improved verbosity, always storing error history, tightened stateErrorFunction parameters, fixed weights handling, filled missing constructor weight arguments, and added solver validations. - Constraints handling and access: added extra checks for vertex/joint indices and provided read-only access to constraints. - Mesh generation and pymomentum target state: improved test character mesh generation and added support for setting the target state in pymomentum. - Skeleton solver and related representations: expanded SkeletonSolverFunction capabilities, added __repr__ for solverOptions, added projection constraint repr, provided introspection for constraint error functions, and added basic slerp functionality for skel_state and quaternion. - Access to error functions: API exposure for accessing error functions. - Quality and stability fixes: fixed Repeatable RNG for Eigen vectors to ensure determinism, enabled Banded QR to support zero bandwidth, and resolved formatting-related issues (fmt vs to_string). Major bugs fixed: - Fixed non-repeatable Eigen random vector generation to ensure determinism where required. - Banded QR now supports bandwidth=0 when n_band=0. - Formatting usage fixes addressing fmt vs to_string edge cases. - Documentation nit fixes (comment for lambda parameter). Overall impact and accomplishments: - Significantly improved reliability, debuggability, and maintainability of the solver workflow, with robust error history and enhanced introspection. These changes enable more predictable behavior in production pipelines, better visibility into error dynamics, and smoother integration with pymomentum workflows. The updated mesh/test generation and target state support streamline testing and on-boarding for new experiments. Technologies and skills demonstrated: - C++/Python binding enhancements, solver architecture refinement, and API design for error functions and constraints. - Enhanced testability through deterministic RNG, improved mesh generation, and explicit error history storage. - Advanced debugging and introspection features (reprs, access APIs, constraint views) to improve developer experience and maintainability.
July 2025
24 Commits • 6 Features
Jul 1, 2025Summary for 2025-07: Key features delivered: - Error Function API and Representation improvements for momentum: added offset support for sequence_state_error_function, bindings for VertexProjectionErrorFunction, and __repr__ implementations for error functions. - Solver core improvements and validations: introduced solver parameter enabling, improved verbosity, always storing error history, tightened stateErrorFunction parameters, fixed weights handling, filled missing constructor weight arguments, and added solver validations. - Constraints handling and access: added extra checks for vertex/joint indices and provided read-only access to constraints. - Mesh generation and pymomentum target state: improved test character mesh generation and added support for setting the target state in pymomentum. - Skeleton solver and related representations: expanded SkeletonSolverFunction capabilities, added __repr__ for solverOptions, added projection constraint repr, provided introspection for constraint error functions, and added basic slerp functionality for skel_state and quaternion. - Access to error functions: API exposure for accessing error functions. - Quality and stability fixes: fixed Repeatable RNG for Eigen vectors to ensure determinism, enabled Banded QR to support zero bandwidth, and resolved formatting-related issues (fmt vs to_string). Major bugs fixed: - Fixed non-repeatable Eigen random vector generation to ensure determinism where required. - Banded QR now supports bandwidth=0 when n_band=0. - Formatting usage fixes addressing fmt vs to_string edge cases. - Documentation nit fixes (comment for lambda parameter). Overall impact and accomplishments: - Significantly improved reliability, debuggability, and maintainability of the solver workflow, with robust error history and enhanced introspection. These changes enable more predictable behavior in production pipelines, better visibility into error dynamics, and smoother integration with pymomentum workflows. The updated mesh/test generation and target state support streamline testing and on-boarding for new experiments. Technologies and skills demonstrated: - C++/Python binding enhancements, solver architecture refinement, and API design for error functions and constraints. - Enhanced testability through deterministic RNG, improved mesh generation, and explicit error history storage. - Advanced debugging and introspection features (reprs, access APIs, constraint views) to improve developer experience and maintainability.
June 2025
7 Commits • 5 Features
Jun 1, 20252025-06 performance summary for facebookresearch/momentum: Expanded asset compatibility, robustness, and configurability across the animation and optimization pipelines. Delivered glTF skeletal animation loading, new IK solver interface with initialization checks, automated VertexProjectionErrorFunction generation, improved error function API exposure and bindings, and advanced mesh-constraint support, alongside a critical validation fix for skinning weights and mesh compatibility. These changes reduce runtime errors, enable external-from-tools assets, and enhance maintainability and optimization workflows, driving faster asset integration and more reliable character pipelines.
7 Commits • 5 Features
Jun 1, 20252025-06 performance summary for facebookresearch/momentum: Expanded asset compatibility, robustness, and configurability across the animation and optimization pipelines. Delivered glTF skeletal animation loading, new IK solver interface with initialization checks, automated VertexProjectionErrorFunction generation, improved error function API exposure and bindings, and advanced mesh-constraint support, alongside a critical validation fix for skinning weights and mesh compatibility. These changes reduce runtime errors, enable external-from-tools assets, and enhance maintainability and optimization workflows, driving faster asset integration and more reliable character pipelines.
June 2025
May 2025
3 Commits • 2 Features
May 1, 2025May 2025 performance summary for facebookresearch/momentum. Focused on delivering feature work to streamline character asset workflows and improve runtime loading, while reducing log noise for faster debugging. Demonstrated strong cross-language integration (C++, pybind, Python) and commitment to performance-conscious engineering.
May 2025
3 Commits • 2 Features
May 1, 2025May 2025 performance summary for facebookresearch/momentum. Focused on delivering feature work to streamline character asset workflows and improve runtime loading, while reducing log noise for faster debugging. Demonstrated strong cross-language integration (C++, pybind, Python) and commitment to performance-conscious engineering.
April 2025
4 Commits • 2 Features
Apr 1, 2025April 2025 momentum monthly summary for facebookresearch/momentum focused on delivering core features, stabilizing data workflows, and enabling broader tool usability. The month featured performance- and accuracy-oriented enhancements to geometry querying, improved IO flexibility for artists, and robust import stability to preserve data integrity across pipelines. Overall, the work strengthens production readiness, reduces manual fixes, and enables more scalable workflows across tools and runtimes.
4 Commits • 2 Features
Apr 1, 2025April 2025 momentum monthly summary for facebookresearch/momentum focused on delivering core features, stabilizing data workflows, and enabling broader tool usability. The month featured performance- and accuracy-oriented enhancements to geometry querying, improved IO flexibility for artists, and robust import stability to preserve data integrity across pipelines. Overall, the work strengthens production readiness, reduces manual fixes, and enables more scalable workflows across tools and runtimes.
April 2025
March 2025
10 Commits • 9 Features
Mar 1, 2025March 2025: Delivered core data-path and API improvements in momentum, delivering tangible business value for downstream ML workflows and tooling. Implemented advanced mesh normals handling with a new with_updated_normals function, enhanced mesh creation to support empty normals, and introduced efficient input handling via pybind11 array_t. Exposed skeleton joint data and added a pre-rotation matrix for easier access to rotation data. Refactored geometry module to return pybind11 array_t directly, reducing copies and improving Python interaction. Fixed a translation_offset bug to return the actual joint.translationOffset. Standardized documentation across modules to improve readability and maintainability. These changes reduce runtime overhead, simplify integration, and improve data correctness for engineering workflows.
March 2025
10 Commits • 9 Features
Mar 1, 2025March 2025: Delivered core data-path and API improvements in momentum, delivering tangible business value for downstream ML workflows and tooling. Implemented advanced mesh normals handling with a new with_updated_normals function, enhanced mesh creation to support empty normals, and introduced efficient input handling via pybind11 array_t. Exposed skeleton joint data and added a pre-rotation matrix for easier access to rotation data. Refactored geometry module to return pybind11 array_t directly, reducing copies and improving Python interaction. Fixed a translation_offset bug to return the actual joint.translationOffset. Standardized documentation across modules to improve readability and maintainability. These changes reduce runtime overhead, simplify integration, and improve data correctness for engineering workflows.
February 2025
11 Commits • 6 Features
Feb 1, 2025February 2025 (2025-02) monthly summary for facebookresearch/momentum. Focused on delivering Python-based maintainability improvements and foundational IK/solver enhancements that reduce maintenance risk, accelerate iteration, and improve gradient-based optimization workflows. Key work includes migrating critical components from C++ to Python, expanding the projection/error framework for per-constraint projections, and enhancing character manipulation through dynamic locator management. Overall, these changes improve code transparency, stability, and extensibility while preserving performance requirements.
11 Commits • 6 Features
Feb 1, 2025February 2025 (2025-02) monthly summary for facebookresearch/momentum. Focused on delivering Python-based maintainability improvements and foundational IK/solver enhancements that reduce maintenance risk, accelerate iteration, and improve gradient-based optimization workflows. Key work includes migrating critical components from C++ to Python, expanding the projection/error framework for per-constraint projections, and enhancing character manipulation through dynamic locator management. Overall, these changes improve code transparency, stability, and extensibility while preserving performance requirements.
February 2025
January 2025
4 Commits • 1 Features
Jan 1, 2025Concise monthly summary for 2025-01: Momentum repo contributions focused on robustness and maintainability of the animation pipeline. Implemented skeleton handling fixes, ensuring root joint preservation during skeleton simplification, correct saving of skeleton state, and improved rotation identity checks. Refactored character loading to construct new Character objects with parameter transforms and limits applied during construction, improving reliability and API clarity. These changes reduce runtime animation glitches, simplify future enhancements, and support smoother asset processing in production.
January 2025
4 Commits • 1 Features
Jan 1, 2025Concise monthly summary for 2025-01: Momentum repo contributions focused on robustness and maintainability of the animation pipeline. Implemented skeleton handling fixes, ensuring root joint preservation during skeleton simplification, correct saving of skeleton state, and improved rotation identity checks. Refactored character loading to construct new Character objects with parameter transforms and limits applied during construction, improving reliability and API clarity. These changes reduce runtime animation glitches, simplify future enhancements, and support smoother asset processing in production.
December 2024
12 Commits • 5 Features
Dec 1, 2024December 2024 (facebookresearch/momentum) delivered substantial feature enhancements, expanded constraint support, and stability fixes that improve robustness, export capabilities, and pipeline performance. Notable progress included separate skeleton simplification API and export refinements, half-plane and linear constraints with Python bindings and serialization, and in-memory GLTF export. Critical bug fixes improved gradient calculation with linear constraints, parameter limit parsing, and pose continuity across missing frames. These efforts push asset processing efficiency, solver accuracy, and developer ergonomics, enabling smoother end-to-end workflows and more reliable asset pipelines.
12 Commits • 5 Features
Dec 1, 2024December 2024 (facebookresearch/momentum) delivered substantial feature enhancements, expanded constraint support, and stability fixes that improve robustness, export capabilities, and pipeline performance. Notable progress included separate skeleton simplification API and export refinements, half-plane and linear constraints with Python bindings and serialization, and in-memory GLTF export. Critical bug fixes improved gradient calculation with linear constraints, parameter limit parsing, and pose continuity across missing frames. These efforts push asset processing efficiency, solver accuracy, and developer ergonomics, enabling smoother end-to-end workflows and more reliable asset pipelines.
December 2024
November 2024
8 Commits • 2 Features
Nov 1, 2024Monthly summary for 2024-11 focused on the facebookresearch/momentum repository. Highlights include delivering high-impact features, fixing critical multi-device issues, and strengthening robustness through enhanced parameter handling and tests.
November 2024
8 Commits • 2 Features
Nov 1, 2024Monthly summary for 2024-11 focused on the facebookresearch/momentum repository. Highlights include delivering high-impact features, fixing critical multi-device issues, and strengthening robustness through enhanced parameter handling and tests.
October 2024
2 Commits • 2 Features
Oct 1, 2024Concise monthly summary for 2024-10: Momentum repo features delivered and impact. Delivered two user-facing enhancements with clear business value and improved code quality.
2 Commits • 2 Features
Oct 1, 2024Concise monthly summary for 2024-10: Momentum repo features delivered and impact. Delivered two user-facing enhancements with clear business value and improved code quality.
October 2024
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Quality Metrics
Correctness94.8%
Maintainability92.4%
Architecture91.0%
Performance86.0%
AI Usage20.2%
Skills & Technologies
Programming Languages
BzlC++CMakeEigenJSONMarkdownPythonSQLStarlarkTOML
Technical Skills
3D Animation3D Geometry3D Graphics3D Math3D Modeling3D Rendering3D TransformationsAPI DesignAPI DevelopmentAlgorithm ImplementationAnimationAutogradAutomatic DifferentiationBVH ImplementationBackend Development
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