Fix transformation matrix docstrings on develop

[AntoineRichard]

Description

Updates the transformation-matrix docstrings in combine_frame_transforms() and subtract_frame_transforms() on develop to state that T_{AB} maps from frame B to frame A, matching #5819 on main.

No new dependencies.

Fixes # N/A - follow-up to #5819 for develop.

Type of change

• Documentation update

Screenshots

Not applicable.

Checklist

• I have read and understood the contribution guidelines
• I have run the pre-commit checks with ./isaaclab.sh --format (./isaaclab.sh -f; all hooks pass except check-git-lfs-pointers, which fails because git-lfs is not installed locally)
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works (not applicable: docstring-only change)
• I have added a changelog fragment under source/<pkg>/changelog.d/ for every touched package (source/isaaclab/changelog.d/antoiner-fix-transform-docs-develop.skip)
• I have added my name to the CONTRIBUTORS.md or my name already exists there (Antoine Richard)

[isaaclab-review-bot]

🤖 Isaac Lab Review Bot

Summary

This PR corrects the docstrings in combine_frame_transforms() and subtract_frame_transforms() to state that T_{AB} maps from frame B to frame A, aligning the develop branch with the fix already merged on main (#5819). The correction is mathematically accurate.

Design Assessment

The notation T_{AB} meaning "transforms points from frame B into frame A" is the standard robotics convention (the subscript reads as "A relative to B" or equivalently "from B to A"). This matches the implementation:

• In combine_frame_transforms: t02 = t01 + quat_apply(q01, t12) correctly composes the chain frame 2 → frame 1 → frame 0, consistent with T_{02} = T_{01} × T_{12} where each T_{XY} maps from Y to X.
• In subtract_frame_transforms: T_{12} = T_{01}^{-1} × T_{02} correctly extracts the frame 2 → frame 1 transform by inverting the frame 1 → frame 0 transform and composing with frame 2 → frame 0.

The parameter descriptions (e.g., "Position of frame 1 w.r.t. frame 0") were already correct and are now consistent with the updated matrix notation explanation.

Findings

No inaccuracies found. The corrected docstrings accurately describe the mathematical convention used in the implementation.

Test Coverage

No new tests needed — pure documentation change.

Verdict

No issues found ✅

[greptile-apps]

Greptile Summary

This PR corrects the docstring convention for T_{AB} in combine_frame_transforms() and subtract_frame_transforms() on the develop branch, aligning it with the equivalent fix already merged to main in #5819. The correction is mathematically consistent with the implementations: T_{01} encodes "frame 1 expressed in frame 0," meaning it maps vectors from frame 1 into frame 0 — i.e., from B to A.

• combine_frame_transforms: updates the T_{AB} description from "frame A to B" to "frame B to A."
• subtract_frame_transforms: applies the same description fix.
• Changelog: adds a .skip fragment to suppress a user-facing changelog entry for this docs-only change.

Confidence Score: 5/5

Safe to merge — purely corrects two docstring lines with no changes to logic, types, or runtime behaviour.

Both changed lines are docstring prose only. The new wording ("from frame B to A") is mathematically consistent with the actual implementations: t02 = t01 + quat_apply(q01, t12) encodes "frame 1 expressed in frame 0," confirming T_{01} maps from frame 1 to frame 0. The .skip changelog fragment correctly suppresses a user-facing entry for a docs-only fix.

No files require special attention.

Important Files Changed

Filename	Overview
source/isaaclab/isaaclab/utils/math.py	Two docstring lines corrected: T_{AB} description updated from "frame A to B" to "frame B to A" in both combine_frame_transforms and subtract_frame_transforms, matching the actual code convention.
source/isaaclab/changelog.d/antoiner-fix-transform-docs-develop.skip	New .skip changelog fragment indicating no user-facing changelog entry is needed for this docstring-only fix.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A["T_01\n(maps frame 1 → frame 0)"] --> C["T_01 × T_12\n= T_02"]
    B["T_12\n(maps frame 2 → frame 1)"] --> C
    C --> D["combine_frame_transforms\nreturns position & orientation\nof frame 2 w.r.t. frame 0"]

    E["T_01\n(maps frame 1 → frame 0)"] --> G["T_01⁻¹ × T_02\n= T_12"]
    F["T_02\n(maps frame 2 → frame 0)"] --> G
    G --> H["subtract_frame_transforms\nreturns position & orientation\nof frame 2 w.r.t. frame 1"]

    style A fill:#d0e8ff
    style B fill:#d0e8ff
    style E fill:#d0e8ff
    style F fill:#d0e8ff
    style D fill:#d4edda
    style H fill:#d4edda

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