---

name: visualization-geometry description: "Use for IKPy transformation-matrix checks, geometry helpers, headless 3D chain plots, target and frame overlays, and URDF tree visualization; do not use it to build chains, solve FK/IK, or control hardware." disable-model-invocation: true metadata: disco-role: operating license: Apache 2.0

Visualization and geometry

Use this sub-skill when a Researcher needs to inspect IKPy transforms or create a visual diagnostic of a chain without connecting to a robot. Start with the matrix and shape rules in the API reference, then select a procedure from the workflows. Keep long-running or repeatable plots headless and save them to an explicit local output path.

Route by responsibility

• Route chain construction, link selection, forward kinematics, inverse kinematics, and joint-vector semantics to chain-kinematics.
• Route URDF/MJCF model loading and parser behavior to robot-model-import. This sub-skill only explains the get_urdf_tree visualization utility after a model path and root link are already known.
• Use the bundled scripts/smoke_plot.py for a dependency and save-path smoke check. It uses an inline toy chain and never reads a robot file or talks to hardware.
• Treat rendered images and DOT/PDF output as diagnostic evidence, not as a motion command, simulator state, or proof that a physical robot is safe.

Operating sequence

1. Establish whether the requested result is a numeric transform inspection, a Matplotlib image, or a Graphviz tree; they have different optional dependencies and failure modes.
2. Check matrix dimensions and the RPY multiplication order before rendering. Inspect the numeric frame first, then use a plot to make frame placement or target error easier to see.
3. In headless environments, select the Matplotlib Agg backend before importing ikpy.utils.plot; call Chain.plot(..., show=False) and save the retained figure explicitly.
4. For a URDF tree, provide an existing URDF path and an exact root link name; inspect the returned DOT/tree objects before asking Graphviz to render.
5. Record output paths, dependency availability, numerical checks, and any clipping or convention assumptions in the downstream experiment log.

See:

• references/api-reference.md for public functions, return shapes, conventions, and optional dependencies.
• references/workflows.md for transform checks, headless plots, target/intermediate-frame overlays, and DOT rendering.
• references/troubleshooting.md for import, backend, shape, plotting, and safety failures.