Implementation:Google deepmind Mujoco MJWarp Collision Primitive Core

Knowledge Sources	Google_deepmind_Mujoco MJWarp Documentation
Domains	Physics_Simulation, GPU_Computing, NVIDIA_Warp
Last Updated	2026-02-15 04:00 GMT

Overview

MJWarp Collision Primitive Core provides the core analytical collision detection functions for primitive geometry pairs as GPU-compatible Warp functions.

Description

This module contains the low-level mathematical implementations of collision detection between primitive geometry types. It provides Warp functions for computing closest points, penetration depths, and contact normals for all supported primitive pairs. These functions implement the analytical geometry formulas from MuJoCo's C engine, translated to run on the GPU via NVIDIA Warp. Utility functions include closest-point-on-segment, segment-to-segment distance, and safe division operations.

Usage

Called by collision_primitive.py wrapper functions to compute the actual collision geometry. These are pure geometric functions that return contact positions, normals, and depths without handling contact parameter computation or output writing.

Code Reference

Source Location

• Repository: Google_deepmind_Mujoco
• File: mjx/mujoco/mjx/third_party/mujoco_warp/_src/collision_primitive_core.py
• Lines: 1-1491

Key Functions

# Utility functions
def safe_div(x, y) -> Any
def normalize_with_norm(x) -> (normalized, norm)
def closest_segment_point(a, b, pt) -> wp.vec3
def closest_segment_point_and_dist(a, b, pt) -> Tuple[wp.vec3, float]
def closest_segment_to_segment_points(a0, a1, b0, b1) -> Tuple[wp.vec3, wp.vec3]

# Primitive collision functions
def plane_sphere(plane_normal, plane_pos, sphere_pos, sphere_radius) -> Tuple[float, wp.vec3]
def sphere_sphere(...)
def sphere_capsule(...)
def capsule_capsule(...)
def plane_capsule(...)
def plane_ellipsoid(...)
def plane_box(...)
def plane_cylinder(...)
def sphere_cylinder(...)
def sphere_box(...)
def capsule_box(...)
def box_box(...)

Import

from mujoco.mjx.third_party.mujoco_warp._src.collision_primitive_core import plane_sphere
from mujoco.mjx.third_party.mujoco_warp._src.collision_primitive_core import sphere_sphere
from mujoco.mjx.third_party.mujoco_warp._src.collision_primitive_core import box_box

I/O Contract

Inputs

Name	Type	Required	Description
pos1	wp.vec3	Yes	Position of first geometry
mat1	wp.mat33	Yes	Rotation matrix of first geometry
size1	wp.vec3	Yes	Size parameters of first geometry
pos2	wp.vec3	Yes	Position of second geometry
mat2	wp.mat33	Yes	Rotation matrix of second geometry
size2	wp.vec3	Yes	Size parameters of second geometry

Outputs

Name	Type	Description
dist	float	Signed distance or penetration depth
pos	wp.vec3	Contact point position
normal	wp.vec3	Contact normal direction

Related Pages

• Environment:Google_deepmind_Mujoco_MJX_Warp_CUDA_Environment