Implementation:Google deepmind Mujoco MJX Warp Collision Driver

Knowledge Sources	Google_deepmind_Mujoco
Domains	Physics Simulation, Collision Detection, GPU Computing, JAX-Warp Bridge
Last Updated	2026-02-15 04:00 GMT

Overview

Auto-generated bridge module that dispatches MuJoCo collision detection computations from JAX to NVIDIA Warp GPU kernels via the MJX FFI layer.

Description

collision_driver.py is an auto-generated file that serves as a shim between the MJX JAX-based physics pipeline and the MuJoCo Warp collision detection backend. It initializes placeholder instances of key MuJoCo Warp dataclasses (Model, Data, Option, Statistic, Contact, Constraint) and defines a _collision_shim function decorated with @ffi.format_args_for_warp that accepts the full set of model geometry parameters (geom types, sizes, AABBs, friction, margins, mesh data, heightfield data) and simulation data arrays needed for broad-phase and narrow-phase collision detection.

Usage

This module is called internally by the MJX pipeline when collision detection is required during a forward simulation step. It bridges JAX array inputs to Warp kernel launches, enabling GPU-accelerated collision computations within a JAX-differentiable simulation graph.

Code Reference

Source Location

• Repository: Google_deepmind_Mujoco
• File: mjx/mujoco/mjx/warp/collision_driver.py
• Lines: 1-410

Key Functions

@ffi.format_args_for_warp
def _collision_shim(
    # Model
    nworld: int,
    block_dim: mjwp_types.BlockDim,
    geom_aabb: wp.array3d(dtype=wp.vec3),
    geom_condim: wp.array(dtype=int),
    geom_dataid: wp.array(dtype=int),
    geom_friction: wp.array2d(dtype=wp.vec3),
    geom_gap: wp.array2d(dtype=float),
    geom_margin: wp.array2d(dtype=float),
    geom_pair_type_count: tuple[int, ...],
    ...
    # Data (contact outputs)
)

Import

from mujoco.mjx.warp import collision_driver

I/O Contract

Inputs

Name	Type	Required	Description
nworld	int	Yes	Number of parallel simulation worlds
block_dim	mjwp_types.BlockDim	Yes	Block dimension configuration for tiled kernel launches
geom_aabb	wp.array3d(vec3)	Yes	Axis-aligned bounding boxes for all geoms
geom_type	wp.array(int)	Yes	Geom type identifiers (sphere, capsule, box, mesh, etc.)
geom_size	wp.array2d(vec3)	Yes	Geom size parameters
geom_friction	wp.array2d(vec3)	Yes	Friction coefficients per geom
mesh_face	wp.array(vec3i)	Yes	Mesh face indices for mesh-type geoms
hfield_data	wp.array(float)	Yes	Heightfield elevation data

Outputs

Name	Type	Description
contact (via Data)	Contact dataclass fields	Detected collision contacts including positions, normals, depths, and friction parameters

Related Pages

• Google_deepmind_Mujoco_MJX_Warp_FFI - FFI helper functions used by the collision driver
• Google_deepmind_Mujoco_MJX_Warp_Forward - Forward dynamics pipeline that invokes collision detection
• Google_deepmind_Mujoco_MJX_Warp_Types - Type definitions for Model, Data, Contact, and Constraint