Spot is Boston Dynamics’ four-legged mobile robot, used for inspection, data capture, and operating in places built for people rather than machines — stairs, gantries, gravel, and the inside of live industrial plant. It is probably the most recognisable legged robot in the world, and a natural thing to want to walk around your own room in AR.
The mechanism
Each of the four legs carries three actuated joints — a hip that abducts sideways, a hip that swings fore-and-aft, and a knee — giving twelve degrees of freedom in the base configuration. The optional Spot Arm adds a six-axis manipulator and a gripper on top of that, bringing the full robot to nineteen actuated joints.
Unlike a parallel mechanism, Spot’s legs are plain serial chains, so the URDF expresses the kinematics completely and ARMOR reproduces them faithfully.
Choosing a variant
The two downloads are genuinely different models, not two levels of detail:
- Base (no arm) is the quadruped alone, built from OBJ meshes with per-link colours
declared in the URDF. It carries no
<collision>and no<inertial>elements at all — it is a visual model. Load it to look at Spot, pose it, and view it in AR; MuJoCo physics has nothing to work with. - With arm is the complete robot including the manipulator, and it is the only one with real physics data: collision primitives on thirteen links and mass plus full inertia tensors on all twenty. The base link alone is declared at 16.7 kg. Its meshes are STL, which carries no colour, so it renders in a flat neutral grey.
In short: pick base to look at it, with arm to simulate it.
About these files
These come from the official Spot SDK, which is where Boston Dynamics publishes the robot’s URDF. ARMOR links to that repository rather than re-hosting anything, so the files you receive are exactly the ones Boston Dynamics publishes, unmodified, and your use of them is governed by their licence.
Each variant is a single ZIP containing the URDF and its meshes together, so it arrives in one download rather than as several dozen separate requests.
