I am trying to import a robot model from Blender to Isaac Sim. In Blender, I created an Armature (skeleton), which I exported as a USD file. I can pose and animate the armature in Blender, but after importing it into Isaac Sim, I can’t move or bend the armature—joints don’t work as expected.
My goal is to design my robot in Blender, export it (including its joints), and then use it in Isaac Sim so the robot can move and be controlled there.
My questions:
What is the recommended workflow for creating a robot in Blender, exporting it as a USD file, and making it usable (with working joints and articulation) in Isaac Sim?
How should I create joints in Blender—including any specific settings or steps—so that the joints or bones are recognized correctly as movable/articulated joints in Isaac Sim?
Are there any tools, plugins, or export settings I need to use to ensure that the armature or joint hierarchy from Blender works properly in Isaac Sim?
Blender’s Armature exports to USD as a skeletal animation hierarchy (Skel/bones for skinning and animation). Isaac Sim’s Robot/Articulation system expects physics articulations—i.e. USD that has an articulation root (UsdPhysicsArticulationRootAPI + PhysX articulation API) on the root link, physics joints (UsdPhysicsRevoluteJoint, UsdPhysicsPrismaticJoint, etc.) between links, and rigid bodies (UsdPhysicsRigidBodyAPI) on each link with mass/collision. Those schemas are different from Skel; a Blender armature USD doesn’t create them, so Isaac Sim doesn’t treat it as a controllable robot.
Recommended workflow: use URDF for the robot, Blender for visuals
The supported way to get a robot with working joints in Isaac Sim is to define the robot as a URDF (or MJCF) and import it via Isaac Sim’s URDF importer, which creates the correct articulation root, joints, and rigid bodies.
Option A — Design in Blender, define in URDF: Model your links and meshes in Blender, export link meshes (e.g. OBJ/STL), then author a URDF where each rigid part is a <link> and each joint is a <joint> (revolute/continuous/prismatic) with the correct parent/child and axis. Import that URDF in Isaac Sim (e.g. File → Import → URDF or the URDF extension). You get one USD with a working articulation. There are no special Blender “joint” settings that make the armature become physics joints—the joint structure has to come from URDF (or an equivalent physics description).
Option B — Use an existing URDF and swap visuals: If you have or can get a URDF for a similar robot, import it in Isaac Sim, then replace or add mesh references in the URDF with your Blender-exported meshes so the look comes from Blender and the behavior from URDF.
Robot Wizard: Isaac Sim’s Robot Wizard can add the articulation root and robot schema to an existing hierarchy, but that hierarchy must already have proper physics joints and rigid bodies (e.g. from a URDF import or from building the USD by hand). It does not convert a Blender armature/Skel into physics joints.
Blender export settings
There are no Blender USD export options that turn an armature into a PhysX articulation. Exporting “armature as USD” gives you Skel/animation data, not the joint/rigid-body structure Isaac Sim needs. So: use Blender for geometry and visuals; use URDF (imported in Isaac Sim) for links, joints, and articulation.
We noticed that this topic hasn’t received any recent updates from anyone reporting this issue, so we are closing it for now to help keep the forum organized.
If you are still experiencing this issue or have related questions, please create a GitHub Discussion or Issue in the Isaac Sim repository and include a link to this topic along with updated details. Mentioning or linking to this original topic provides helpful context and makes it easier for others to assist you.
Thank you for being part of the NVIDIA Isaac Sim community.