Add PersonSkeleton to osi_common and skeleton field to Occupant

Add a common PersonSkeleton message in osi_common.proto that provides a
generic, reusable skeleton model for any person representation (occupants,
pedestrians, etc.). The skeleton uses the same bone hierarchy and naming
convention as the existing MovingObject.PedestrianAttributes.Bone.

Extend the Occupant message with an optional skeleton field that references
the new PersonSkeleton type. The skeleton root is anchored relative to the
vehicle bounding box center, following the bbcenter_to_rear/front pattern.

Add migration notes to PedestrianAttributes indicating the local Bone
definition will be replaced by the common PersonSkeleton type in OSI 4.

The Bone message is duplicated because Protocol Buffers does not support
message type aliases, and changing PedestrianAttributes would be a breaking
change. Clear comments document this and the planned OSI 4 consolidation.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: jdsika

osi_common.proto

@@ -1104,3 +1104,216 @@ message Polygon3d
     //
     repeated Vector3d vertex = 1;
 }
+
+//
+// \brief A skeleton representing the posture of a person.
+//
+// This is a generic skeleton model that can be used for any person
+// representation, such as vehicle occupants or pedestrians.
+//
+// The skeleton is defined relative to a root point. The root point itself
+// is positioned relative to the bounding box center of the containing
+// entity using \c #bbcenter_to_root.
+//
+// \note The \c Bone message and \c Bone::Type enum are structurally
+// equivalent to the ones defined in
+// \c MovingObject::PedestrianAttributes::Bone. The duplication exists
+// because Protocol Buffers does not support message type aliases,
+// and \c PedestrianAttributes::Bone cannot be changed without a breaking
+// change. In OSI 4, \c MovingObject::PedestrianAttributes is planned to
+// adopt this common \c PersonSkeleton type, eliminating the duplication.
+//
+message PersonSkeleton
+{
+    // Position offset from the bounding box center of the containing entity
+    // to the current position of the root point of the skeleton model.
+    //
+    // For an occupant this is the offset from the vehicle's bounding box
+    // center (\c MovingObject::base . \c BaseMoving::position) to the
+    // skeleton root, analogous to
+    // \c MovingObject::VehicleAttributes::bbcenter_to_rear.
+    //
+    // For a pedestrian this is the offset from the pedestrian's bounding
+    // box center to the skeleton root, analogous to
+    // \c MovingObject::PedestrianAttributes::bbcenter_to_root.
+    //
+    optional Vector3d bbcenter_to_root = 1;
+
+    // List of all bones of the person.
+    //
+    // The number of bones may vary, based on the detail level of
+    // the model used. For example, some simulators will not include
+    // detailed data about the hands.
+    //
+    // \note A bone of each type can be provided, or left out, depending
+    // on the desired level of detail, or available data. However, if a
+    // bone is defined, all bones in the chain from that bone back to
+    // the root point must be provided to create a complete chain.
+    //
+    repeated Bone skeleton_bone = 2;
+
+    //
+    // \brief A bone in the skeleton of a person.
+    //
+    // Each point represents a joint, or otherwise important point in the
+    // skeleton. For example pelvis, knee or shoulder. The naming convention
+    // should be followed for identifying bones.
+    //
+    // \note This message is structurally equivalent to
+    // \c MovingObject::PedestrianAttributes::Bone. See the note on
+    // \c PersonSkeleton for the rationale behind the duplication.
+    //
+    message Bone
+    {
+        // Bones are identified by their type, combined with which body side
+        // they are on.
+        //
+        // To properly identify the bones the pre-defined naming convention
+        // must be used.
+        //
+        // \image html OSI_SkeletonNamingConvention.svg
+        //
+        // A bone's name, position, and orientation is defined by the end-point
+        // closer to the root. For example: the "LOWER_ARM_L" will define the
+        // point in the left elbow of the model.
+        //
+        // If a bone which is more than one layer detached from the
+        // root point is used, all bones between that bone and the root also
+        // need to be defined in order to create a complete chain!
+        //
+        // If information about bones are missing, they may be left empty.
+        //
+        optional Type type = 1;
+
+        // Position of the bone.
+        //
+        // Reference system is the root, defined by
+        // \c PersonSkeleton::bbcenter_to_root.
+        //
+        optional Vector3d position = 2;
+
+        // Orientation of the bone.
+        //
+        // Reference system is the root, defined by
+        // \c PersonSkeleton::bbcenter_to_root.
+        //
+        optional Orientation3d orientation = 3;
+
+        // Length of the bone.
+        //
+        // Measured along its major axis.
+        //
+        // Unit: m
+        //
+        optional float length = 4;
+
+        // Determines whether a bone is explicitly missing from the model.
+        //
+        // In case a person has missing limbs this can be explicitly
+        // communicated by setting this boolean to TRUE.
+        //
+        optional bool missing = 5;
+
+        // The velocity of the bone.
+        //
+        // Reference system is the root, defined by
+        // \c PersonSkeleton::bbcenter_to_root.
+        //
+        optional Vector3d velocity = 6;
+
+        // The orientation rate of the bone.
+        //
+        // Reference system is the root, defined by
+        // \c PersonSkeleton::bbcenter_to_root.
+        //
+        optional Orientation3d orientation_rate = 7;
+
+        // The type of the bone.
+        //
+        // \image html OSI_PedestrianModelHierarchy.jpg
+        //
+        enum Type
+        {
+            // Root point of the person. Defined by
+            // \c PersonSkeleton::bbcenter_to_root.
+            //
+            TYPE_ROOT = 0;
+
+            // Bone defining the hip.
+            //
+            TYPE_HIP = 1;
+
+            // Bone defining the lower part of the spine.
+            //
+            TYPE_LOWER_SPINE = 2;
+
+            // Bone defining the upper part of the spine.
+            //
+            TYPE_UPPER_SPINE = 3;
+
+            // Bone defining the neck.
+            //
+            TYPE_NECK = 4;
+
+            // Bone defining the head.
+            //
+            TYPE_HEAD = 5;
+
+            // Bone defining the left shoulder.
+            //
+            TYPE_SHOULDER_L = 6;
+
+            // Bone defining the right shoulder.
+            //
+            TYPE_SHOULDER_R = 7;
+
+            // Bone defining the left upper arm.
+            //
+            TYPE_UPPER_ARM_L = 8;
+
+            // Bone defining the right upper arm.
+            //
+            TYPE_UPPER_ARM_R = 9;
+
+            // Bone defining the left forearm.
+            //
+            TYPE_LOWER_ARM_L = 10;
+
+            // Bone defining the right forearm.
+            //
+            TYPE_LOWER_ARM_R = 11;
+
+            // Bone defining the left hand.
+            //
+            TYPE_FULL_HAND_L = 12;
+
+            // Bone defining the right hand.
+            //
+            TYPE_FULL_HAND_R = 13;
+
+            // Bone defining the left thigh.
+            //
+            TYPE_UPPER_LEG_L = 14;
+
+            // Bone defining the right thigh.
+            //
+            TYPE_UPPER_LEG_R = 15;
+
+            // Bone defining the left shin.
+            //
+            TYPE_LOWER_LEG_L = 16;
+
+            // Bone defining the right shin.
+            //
+            TYPE_LOWER_LEG_R = 17;
+
+            // Bone defining the left foot.
+            //
+            TYPE_FULL_FOOT_L = 18;
+
+            // Bone defining the right foot.
+            //
+            TYPE_FULL_FOOT_R = 19;
+        }
+    }
+}

osi_object.proto

@@ -1302,6 +1302,13 @@ message MovingObject
     // This is an extension to the \c MovingObject with additional information
     // describing a pedestrian in more detail.
     //
+    // \note The skeleton data (\c #bbcenter_to_root and \c Bone) in this
+    // message is structurally equivalent to the common
+    // \c PersonSkeleton type defined in osi_common.proto. In OSI 4, this
+    // message is planned to use \c PersonSkeleton directly, replacing the
+    // local definitions. For new integrations, consider using
+    // \c PersonSkeleton where possible.
+    //
     message PedestrianAttributes
     {
         // Position offset from the center of the bounding box to the current position

osi_occupant.proto

@@ -36,6 +36,19 @@ message Occupant
     //
     repeated ExternalReference source_reference = 3;
 
+    // The skeleton of the occupant.
+    //
+    // The skeleton represents the posture and body structure of the occupant
+    // within the host vehicle. Bone positions and orientations are defined
+    // relative to the skeleton root point.
+    //
+    // The \c PersonSkeleton::bbcenter_to_root field provides the offset
+    // from the vehicle's bounding box center
+    // (\c MovingObject::base . \c BaseMoving::position) to the skeleton
+    // root point.
+    //
+    optional PersonSkeleton skeleton = 4;
+
     //
     // \brief Information regarding the classification of the occupant.
     //