Fixes source frame indexing in FrameTransfomer sensor (#350)

# Description

The FrameTransformer sensor always assumed that the source frame index
is 0 in the parsed regex expression. However, a recent issue appeared
where this is not the case, and it led to a bug due to the hard-coded
value. This MR fixes the source frame index in the sensor and also adds
a unit test to check this behavior.

Fixes: #170

## Type of change

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

## Checklist

- [x] I have run the [`pre-commit` checks](https://pre-commit.com/) with
`./orbit.sh --format`
- [x] I have made corresponding changes to the documentation
- [x] My changes generate no new warnings
- [x] I have added tests that prove my fix is effective or that my
feature works
- [x] I have run all the tests with `./orbit.sh --test` and they pass
- [x] I have updated the changelog and the corresponding version in the
extension's `config/extension.toml` file
- [x] I have added my name to the `CONTRIBUTORS.md` or my name already
exists there

---------

Co-authored-by: Mayank Mittal <mittalma@leggedrobotics.com>

source/extensions/omni.isaac.orbit/config/extension.toml

@@ -1,7 +1,7 @@
 [package]
 
 # Note: Semantic Versioning is used: https://semver.org/
-version = "0.10.11"
+version = "0.10.12"
 
 # Description
 title = "ORBIT framework for Robot Learning"

source/extensions/omni.isaac.orbit/docs/CHANGELOG.rst

@@ -1,6 +1,27 @@
 Changelog
 ---------
 
+0.10.12 (2024-01-10)
+~~~~~~~~~~~~~~~~~~~~
+
+Fixed
+^^^^^
+
+* Fixed indexing of source and target frames in the :class:`omni.isaac.orbit.sensors.FrameTransformer` class.
+  Earlier, it always assumed that the source frame body is at index 0. Now, it uses the body index of the
+  source frame to compute the transformation.
+
+Deprecated
+^^^^^^^^^^
+
+* Renamed quantities in the :class:`omni.isaac.orbit.sensors.FrameTransformerData` class to be more
+  consistent with the terminology used in the asset classes. The following quantities are deprecated:
+
+  * ``target_rot_w`` -> ``target_quat_w``
+  * ``source_rot_w`` -> ``source_quat_w``
+  * ``target_rot_source`` -> ``target_quat_source``
+
+
 0.10.11 (2024-01-08)
 ~~~~~~~~~~~~~~~~~~~~
 

source/extensions/omni.isaac.orbit/omni/isaac/orbit/sensors/frame_transformer/frame_transformer_data.py

@@ -6,6 +6,7 @@
 from __future__ import annotations
 
 import torch
+import warnings
 from dataclasses import dataclass
 
 
@@ -14,40 +15,75 @@ class FrameTransformerData:
     """Data container for the frame transformer sensor."""
 
     target_frame_names: list[str] = None
-    """Target frame names (this denotes the order that frame data will be ordered).
+    """Target frame names (this denotes the order in which that frame data is ordered).
 
     The frame names are resolved from the :attr:`FrameTransformerCfg.FrameCfg.name` field.
-    This usually follows the order in which the frames are defined in the config. However, in the case of
-    regex matching, the order may be different.
+    This usually follows the order in which the frames are defined in the config. However, in
+    the case of regex matching, the order may be different.
     """
 
     target_pos_source: torch.Tensor = None
     """Position of the target frame(s) relative to source frame.
 
     Shape is (N, M, 3), where N is the number of environments, and M is the number of target frames.
     """
-    target_rot_source: torch.Tensor = None
+
+    target_quat_source: torch.Tensor = None
     """Orientation of the target frame(s) relative to source frame quaternion (w, x, y, z).
 
     Shape is (N, M, 4), where N is the number of environments, and M is the number of target frames.
     """
+
     target_pos_w: torch.Tensor = None
     """Position of the target frame(s) after offset (in world frame).
 
     Shape is (N, M, 3), where N is the number of environments, and M is the number of target frames.
     """
-    target_rot_w: torch.Tensor = None
+
+    target_quat_w: torch.Tensor = None
     """Orientation of the target frame(s) after offset (in world frame) quaternion (w, x, y, z).
 
     Shape is (N, M, 4), where N is the number of environments, and M is the number of target frames.
     """
+
     source_pos_w: torch.Tensor = None
     """Position of the source frame after offset (in world frame).
 
     Shape is (N, 3), where N is the number of environments.
     """
-    source_rot_w: torch.Tensor = None
+
+    source_quat_w: torch.Tensor = None
     """Orientation of the source frame after offset (in world frame) quaternion (w, x, y, z).
 
     Shape is (N, 4), where N is the number of environments.
     """
+
+    @property
+    def target_rot_source(self) -> torch.Tensor:
+        """Alias for :attr:`target_quat_source`.
+
+        .. deprecated:: v0.2.1
+            Use :attr:`target_quat_source` instead. Will be removed in v0.3.0.
+        """
+        warnings.warn("'target_rot_source' is deprecated, use 'target_quat_source' instead.", DeprecationWarning)
+        return self.target_quat_source
+
+    @property
+    def target_rot_w(self) -> torch.Tensor:
+        """Alias for :attr:`target_quat_w`.
+
+        .. deprecated:: v0.2.1
+            Use :attr:`target_quat_w` instead. Will be removed in v0.3.0.
+        """
+        warnings.warn("'target_rot_w' is deprecated, use 'target_quat_w' instead.", DeprecationWarning)
+        return self.target_quat_w
+
+    @property
+    def source_rot_w(self) -> torch.Tensor:
+        """Alias for :attr:`source_quat_w`.
+
+        .. deprecated:: v0.2.1
+            Use :attr:`source_quat_w` instead. Will be removed in v0.3.0.
+        """
+        warnings.warn("'source_rot_w' is deprecated, use 'source_quat_w' instead.", DeprecationWarning)
+        return self.source_quat_w