Fixes Warp kernel compilation error in Fabric backend

[emmanuel-ferdman]

Description

The Fabric backend uses wp.transform_compose to build transformation matrices, but this function was added in Warp 1.7. Isaac Sim 4.5 ships with Warp 1.5, so the kernel fails to compile when calling set_world_poses on cameras or other prims with Fabric enabled. This PR replaces the missing function with inline matrix math using wp.quat_to_matrix, which exists in Warp 1.5.

Fixes #4529

Type of change

• Bug fix (non-breaking change which fixes an issue)

Screenshots

N/A - this is a runtime error fix, no visual changes.

Checklist

• I have read and understood the contribution guidelines
• I have run the pre-commit checks with ./isaaclab.sh --format
• 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
• I have updated the changelog and the corresponding version in the extension's config/extension.toml file
• I have added my name to the CONTRIBUTORS.md or my name already exists there

[greptile-apps]

Greptile Overview

Greptile Summary

This PR fixes a runtime compilation error in the Fabric backend by replacing wp.transform_compose() (introduced in Warp 1.7) with inline matrix math that works with Warp 1.5, which ships with Isaac Sim 4.5.

Key changes:

• Replaced wp.transform_compose() call with manual transformation matrix construction
• Uses wp.quat_to_matrix() to convert quaternion to 3x3 rotation matrix
• Applies scale by multiplying each column of the rotation matrix by the corresponding scale component
• Constructs 4x4 transformation matrix with scaled rotation and position components
• Maintains the transpose operation for column-major ordering compatibility

Technical correctness:
The implementation correctly composes a TRS (Translation-Rotation-Scale) transformation matrix. The scale application matches the decomposition logic in _decompose_transformation_matrix(), which extracts scale as column vector magnitudes. The mathematical approach is sound and equivalent to what wp.transform_compose() would produce.

Confidence Score: 5/5

• This PR is safe to merge with no identified risks
• The fix correctly addresses a real backward compatibility issue without introducing new bugs. The inline matrix math is mathematically equivalent to the Warp 1.7 function it replaces, properly handling the TRS transformation composition. The implementation matches the existing decomposition logic, ensuring round-trip consistency.
• No files require special attention

Important Files Changed

Filename	Overview
source/isaaclab/isaaclab/utils/warp/fabric.py	Replaces wp.transform_compose (Warp 1.7+) with inline matrix math using wp.quat_to_matrix for Warp 1.5 compatibility

Sequence Diagram

sequenceDiagram
    participant Client as Client Code
    participant Kernel as compose_fabric_transformation_matrix_from_warp_arrays
    participant Warp as Warp Library
    participant Fabric as Fabric Backend
    
    Client->>Kernel: Call with positions, orientations, scales
    Kernel->>Kernel: Get fabric index from mapping
    Kernel->>Fabric: Read current transformation matrix
    Kernel->>Kernel: Decompose to get existing values
    Kernel->>Kernel: Update position, rotation, scale from input arrays
    Kernel->>Warp: wp.quat_to_matrix(rotation)
    Warp-->>Kernel: 3x3 rotation matrix
    Kernel->>Kernel: Apply scale to each column of rotation matrix
    Note over Kernel: m00=rot[0,0]*scale[0], m01=rot[0,1]*scale[1], etc.
    Kernel->>Kernel: Construct 4x4 matrix with scaled rotation + position
    Kernel->>Warp: wp.mat44f(...) then wp.transpose()
    Warp-->>Kernel: Transposed matrix (column-major)
    Kernel->>Warp: wp.mat44d() cast to double precision
    Warp-->>Kernel: Final transformation matrix
    Kernel->>Fabric: Write matrix to fabric_matrices[fabric_index]
    Kernel-->>Client: Transform updated in Fabric

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