Skip unused PyTorch3D extensions for GR00T

[jaybdub]

Description

Updates the GR00T installation instructions to install PyTorch3D with native extensions disabled. GR00T only uses pytorch3d.transforms, so this avoids the failing Pulsar CUDA link on DGX Spark without removing required functionality.

Tracks NVBug 6288216.

Type of change

• Bug fix
• Documentation update

Release backport

• Backport this pull request to the active release branch after it merges into develop

Validation

• uv run --isolated --extra test -- make -C docs current-docs
• uv run isaaclab -f
• Installed PyTorch3D 0.7.9 with PYTORCH3D_NO_EXTENSION=1 and ran GR00T-compatible GPU rotation transforms inside Isaac Sim 6.0.1.
• The original DGX Spark/aarch64 host was unavailable, so architecture-specific validation remains for CI or the reporter.

Screenshots

Not applicable.

Checklist

• I have read and understood the contribution guidelines.
• I have run the pre-commit checks.
• I have made the corresponding documentation change.
• My changes generate no new warnings.
• I have run targeted validation for the fix.
• Changelog fragment is not applicable to this docs-only change.
• The contributor already appears in repository revision history.

[greptile-apps]

Confidence Score: 5/5

The PR appears safe to merge with no actionable issues identified.

Summary

• Adds PYTORCH3D_NO_EXTENSION=1 to avoid CUDA extension link failures.
• Explains why the transforms-only installation remains sufficient.

[isaaclab-review-bot]

Isaac Lab Review Bot

The documentation now installs PyTorch3D 0.7.9 with native extensions disabled for the GR00T N1.5 workflow, avoiding the failing CUDA renderer build while retaining the documented transforms-only usage.

• Design and architecture: The change is confined to the GR00T installation boundary and leaves Isaac Lab modules, dataset conversion, finetuning, and rollout paths unchanged. The key tradeoff is that this documented environment will not support future GR00T use of compiled PyTorch3D operators without revisiting the installation command.
• API: No Isaac Lab public APIs, CLI arguments, exports, or package configuration are changed. The affected compatibility surface is the documented PyTorch3D installation: pure-Python transforms remain available, while compiled rendering and other native operators are intentionally unavailable.
• Implementation: The environment-variable prefix and shell continuation form a valid single installation command. Removing MAX_JOBS is consistent with disabling native compilation. Targeted transforms validation is reported, with architecture-specific aarch64 Blackwell validation appropriately remaining as residual risk.

No blocking issues. No inline issue met the actionable-evidence threshold; the assessment above records the review feedback.

Automated review; human maintainers own approval decisions.