Add skeleton profiles, a tactile schema and tracker, and a tactile example

docs/source/device/tactile/index.rst

@@ -5,7 +5,8 @@ Tactile devices
 ===============
 
 Tactile devices capture contact measurements. For actuator output, see
-:doc:`/references/haptic_feedback`.
+:doc:`/references/haptic_feedback`. A device can publish through the vendor-neutral
+:doc:`/references/tactile_schema`.
 
 .. toctree::
    :maxdepth: 1

docs/source/index.rst

@@ -92,6 +92,8 @@ Table of Contents
    references/requirements
    references/build
    references/generated_trackers
+   references/skeleton_binding
+   references/tactile_schema
    references/retargeting/index
    references/device_provider_monitoring
    references/camera_streaming

docs/source/references/generated_trackers.rst

@@ -86,10 +86,10 @@ example) declares that description as the tracker's ``metadata`` table:
    [[tracker]]
    name = "tactile"
    table = "TactileData"
-   metadata = "TactileShape"
+   metadata = "TactileMetadata"
 
 The metadata table is the ``root_type`` of a schema of its own, named after the table in snake case
-(``tactile_shape.fbs``), with no Record wrapper: MCAP records the table itself. Like the data table,
+(``tactile_metadata.fbs``), with no Record wrapper: MCAP records the table itself. Like the data table,
 it needs a hand-written ``schema/python/*_bindings.h`` before ``get_metadata()`` can return it to
 Python. Only ``direction = "pull"`` supports ``metadata``.
 
@@ -154,6 +154,9 @@ Generated today
    * - ``gamepad``
      - ``GamepadTracker``
      - Gamepad state pushed by the gamepad plugin (SDL3); only ``python_accessor`` is overridden
+   * - ``tactile``
+     - ``TactileTracker``
+     - Taxel readings with a ``TactileMetadata`` device description; see :doc:`tactile_schema`
 
 Still hand-written
 ------------------

docs/source/references/skeleton_binding.rst

@@ -0,0 +1,77 @@
+.. SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+.. SPDX-License-Identifier: Apache-2.0
+
+Skeleton Binding
+================
+
+A device that describes rigid segments — the links a tactile glove's taxels are skinned to,
+for example — carries a ``SkeletonBinding`` that names each segment in a skeleton whose pose
+some other source provides at run time. The schema is
+:code-file:`src/core/schema/fbs/skeleton_binding.fbs`; the registry and the checks below are
+:code-file:`src/core/schema/cpp/inc/schema/skeleton_binding.hpp`.
+
+``segment_names[i]`` names segment ``i`` of the device. ``profile`` says which skeleton the names
+come from; without it the binding is *generic* and the names are labels only. ``asset`` identifies
+an external description, such as a URDF, that a profile names segments in.
+
+Registered profiles
+-------------------
+
+.. list-table::
+   :header-rows: 1
+
+   * - ``id``
+     - ``version``
+     - Segment names
+     - Requires
+   * - ``openxr.hand``
+     - 1
+     - ``HandJoint`` names (``PALM`` … ``LITTLE_TIP``), the XR_EXT_hand_tracking joints
+     - ``side`` LEFT or RIGHT
+   * - ``openxr.body.bd``
+     - 1
+     - ``BodyJoint`` names (``PELVIS`` … ``RIGHT_HAND``), the XR_BD_body_tracking joints
+     - —
+   * - ``urdf.link``
+     - 1
+     - ``<link name>`` values of the URDF in ``asset``
+     - ``asset``
+
+A profile's names never change within a version; a change takes a new ``version``. Ids outside
+this table are valid and read as generic bindings. Vendor profiles take a reverse-DNS prefix,
+such as ``com.example.glove``.
+
+Rules
+-----
+
+``validate_skeleton_binding(binding, segment_count, side)`` returns an empty string for a valid
+binding, otherwise the first rule it breaks:
+
+#. ``segment_names`` has exactly ``segment_count`` entries, each non-empty and unique.
+#. ``asset.digest``, when present, is an RFC 6920 SHA-256 name: ``ni:///sha-256;`` and the
+   43-character unpadded base64url digest of the asset's bytes.
+#. An ``asset`` needs a ``profile``.
+#. ``profile.id`` is two or more dot-separated tokens of ``[a-z0-9_]``, each starting with a
+   letter; ``profile.version`` is at least 1.
+#. For a registered profile: ``asset`` is present exactly when the profile requires one, ``side``
+   is LEFT or RIGHT when the profile requires it, and every name is one of the profile's names.
+
+Checking names against an asset needs its bytes, so it is a separate step in Python:
+``check_skeleton_asset(binding, data)`` verifies the digest and, for ``urdf.link``, that every name
+is a link of the URDF. ``asset_digest(data)`` computes the digest to store.
+
+.. code-block:: python
+
+   from isaaccapture.schema import (
+       AssetRef, SkeletonBinding, SkeletonProfileRef, asset_digest, check_skeleton_asset,
+       validate_skeleton_binding,
+   )
+
+   urdf = open("glove.urdf", "rb").read()
+   binding = SkeletonBinding(
+       ["base_link", "index_tip"],
+       profile=SkeletonProfileRef("urdf.link", 1),
+       asset=AssetRef(asset_digest(urdf), "package://glove/glove.urdf", "application/xml"),
+   )
+   assert validate_skeleton_binding(binding, segment_count=2) == ""
+   assert check_skeleton_asset(binding, urdf) == ""

docs/source/references/tactile_schema.rst

@@ -0,0 +1,70 @@
+.. SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+.. SPDX-License-Identifier: Apache-2.0
+
+Tactile Schema
+==============
+
+A tactile device publishes through the generated ``TactileTracker``: a ``TactileMetadata`` once per
+session as the tracker's :ref:`metadata <tracker-metadata>`, and a ``TactileData`` every frame. The
+schemas are :code-file:`src/core/schema/fbs/tactile_metadata.fbs` and
+:code-file:`src/core/schema/fbs/tactile.fbs`; the checks below are
+:code-file:`src/core/schema/cpp/inc/schema/tactile_validation.hpp`.
+
+Device description
+------------------
+
+``TactileMetadata`` holds:
+
+- ``device`` — vendor, model, serial number, firmware, ``side`` (a ``BodySide``), nominal rate and
+  calibration id.
+- ``shape`` — the rigid ``segments`` of the device, each with its bind pose, and the ``taxels``, each
+  with its pose and up to four skinning weights over the segments. Both are in the device frame at
+  the reference configuration. ``taxel_areas`` optionally gives each taxel's area in m².
+- ``binding`` — a :doc:`skeleton_binding` naming each segment in the skeleton that poses it. Without
+  one the segments are not posed by anything and the taxels stay at their bind poses.
+- ``channels`` — which ``TactileData`` vectors the device fills.
+- ``extensions`` — vendor data, each named by a registry id such as ``com.example.glove``.
+
+A taxel's frame has +Z along the outward surface normal and +X along the shear x axis. Its position
+at run time is
+
+.. code-block:: text
+
+   p = sum_k weights[k] * T_current[segments[k]] * inverse(T_bind[segments[k]]) * p_bind
+
+where ``T_current`` is the segment's pose from the bound skeleton, and ``p`` comes out in the frame
+that skeleton is posed in. The taxel's axes blend the same way and are renormalized.
+
+Per-frame data
+--------------
+
+Entry *i* of each ``TactileData`` vector is taxel *i* of the shape. Forces are what the contacted
+surface exerts on the taxel, in newtons:
+
+- ``normal_force`` — along the taxel normal; positive presses into the surface.
+- ``shear_force`` — along the taxel frame's +X and +Y.
+- ``raw`` — ``channels.raw_values_per_taxel`` uncalibrated readings per taxel.
+- ``taxel_state`` — ``VALID``, ``SATURATED``, ``INVALID`` or ``UNAVAILABLE``; when absent, every
+  taxel is ``VALID``.
+- ``sequence`` — the device's frame counter, when it has one.
+
+Rules
+-----
+
+``validate_tactile_metadata(metadata)`` returns an empty string for a valid description, otherwise
+the first rule it breaks. The Python ``TactileMetadata`` constructor raises ``ValueError`` with the
+same message.
+
+#. ``shape`` has at least one segment and one taxel.
+#. Every bind pose and taxel pose is finite, with an orientation of norm 1 within 1e-3.
+#. Each taxel's weights are finite and nonnegative and sum to 1 within 1e-5. A slot with a nonzero
+   weight names an existing segment that no other slot of the taxel names; a zero-weight slot
+   holds segment 0.
+#. ``taxel_areas`` is empty or holds one finite, positive value per taxel.
+#. ``channels`` is present and declares normal force, shear force or raw readings.
+#. ``binding``, when present, passes ``validate_skeleton_binding`` for the shape's segments and
+   ``device.side``.
+#. Extension ids are registry ids and unique.
+
+``validate_tactile_data(data, metadata)`` checks that a frame fills exactly the declared vectors,
+with one entry per taxel (``raw_values_per_taxel`` per taxel for ``raw``).

examples/CMakeLists.txt

@@ -19,6 +19,7 @@ if(BUILD_EXAMPLES)
     add_subdirectory(deviceio_live_view)
     add_subdirectory(soma_body_publisher)
     add_subdirectory(soma_hand_publisher)
+    add_subdirectory(tactile)
     add_subdirectory(haptic_feedback)
     add_subdirectory(sharpa_avatar)
     add_subdirectory(vehicle_teleop)

examples/tactile/CMakeLists.txt

@@ -0,0 +1,7 @@
+# SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+
+cmake_minimum_required(VERSION 3.20)
+
+include(${CMAKE_SOURCE_DIR}/cmake/InstallPythonExample.cmake)
+install_python_example(DESTINATION examples/tactile)

examples/tactile/README.md

@@ -0,0 +1,30 @@
+<!--
+SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+SPDX-License-Identifier: Apache-2.0
+-->
+
+# Tactile feeder and printer
+
+1. In the Python environment that has Isaac Capture installed, install the example from the
+   repository root:
+
+   ```bash
+   uv pip install -e ./examples/tactile
+   ```
+
+2. Start the printer. It starts the CloudXR runtime if none is running:
+
+   ```bash
+   python -m isaaccapture_examples.tactile.printer --accept-eula
+   ```
+
+3. In a second terminal with the same environment, start the feeder:
+
+   ```bash
+   python -m isaaccapture_examples.tactile.feeder
+   ```
+
+4. In the printer terminal, check that a `TactileMetadata` block is printed once, followed by a
+   `TactileData` block with the values of taxel 0 and taxel 15 every second.
+
+5. Press `Ctrl+C` in the feeder terminal, then in the printer terminal.

examples/tactile/pyproject.toml

@@ -0,0 +1,23 @@
+# SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+
+[build-system]
+requires = ["hatchling"]
+build-backend = "hatchling.build"
+
+[project]
+name = "isaaccapture-examples-tactile"
+version = "0.0.0"
+description = "Isaac Capture tactile feeder and printer"
+requires-python = ">=3.11,<3.14"
+dependencies = [
+    "isaaccapture[cloudxr]",
+    "numpy>=1.23.0",
+]
+
+[tool.hatch.build.targets.wheel]
+only-include = ["python/isaaccapture_examples/tactile"]
+sources = ["python"]
+
+[tool.uv.sources]
+isaaccapture = { path = "../..", editable = true }

examples/tactile/python/isaaccapture_examples/tactile/__init__.py

@@ -0,0 +1,2 @@
+# SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0

examples/tactile/python/isaaccapture_examples/tactile/common.py

@@ -0,0 +1,9 @@
+# SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+
+"""Values the feeder and the printer must agree on."""
+
+DEFAULT_COLLECTION_ID = "tactile"
+
+# TactileTracker's default max_flatbuffer_size (trackers.toml); a larger collection is rejected.
+TACTILE_MAX_PAYLOAD_SIZE = 32768