Xacro Support

Many real robot descriptions — especially ROS-native ones like the Franka Emika Panda and FR3 — aren’t published as a plain URDF at all, but as Xacro (.xacro), an XML macro language layered on top of URDF. ARMOR expands Xacro on-device, so you can import a robot straight from its native repository without running a separate build step first.

What gets expanded

When you load a .xacro file (or select a folder whose entry point is one), ARMOR’s Xacro preprocessor resolves:

• Macros (<xacro:macro> / <xacro:call> and shorthand macro-tag invocations), evaluated with true dynamic scoping — a macro body sees its caller’s parameters, not a flattened global namespace.
• Includes (<xacro:include filename="$(find package)/...">), followed recursively, with $(find <package>) resolved against the folder structure you imported.
• Conditionals (<xacro:if> / <xacro:unless>), so branches that evaluate false are skipped entirely rather than producing invalid XML.
• Arguments and properties (<xacro:arg>, <xacro:property>, including lazy_eval="false" properties and ${...} Python-style expressions).
• Block insertion (<xacro:insert_block>) and YAML property loading (xacro.load_yaml).

The result is expanded into a real, in-memory URDF — links, joints, and mesh references — the same representation ARMOR uses for any other robot, so every editor, viewer, and export feature works identically afterward. There’s nothing in the app that distinguishes a robot that started as Xacro from one that started as a plain URDF once it’s imported.

The Franka Emika Panda, imported straight from its Xacro-only source repository — same viewer, editor, and export tools as any other robot.

What this means in practice

• You can import directly from a repository’s own urdf/ or robots/ folder, even when it only contains .xacro files — no separate expansion tool needed.
• Robots with parametric variants driven by $(arg ...) (for example, an arm with an optional gripper attachment) expand differently depending on which variant you select — see the robot’s own documentation or gallery entry for which arguments distinguish its variants.
• A malformed or incomplete Xacro tree (a missing include, a macro that references an undefined property) fails to expand the same way an invalid URDF fails to parse — see Validating for what that looks like.

Next Steps

• Loading URDF Files — the general import flow, including supported formats.
• Robot Gallery & Deep Links — several gallery robots are delivered as Xacro trees and expanded automatically on import.
• Finding URDF Files — where to find robot descriptions, including Xacro-only sources.