Hand Pose

Overview

Hand pose is a 21-joint skeleton per hand (wrist plus five fingers, four joints each) in the world frame. Each joint has position (x, y, z in meters) and orientation (quaternion w, x, y, z). Left and right use separate topics with the same joint layout.

Coordinate Frame

• Reference frame: World.
• Axes: X forward, Y left, Z up (right-handed).
• Units: Position in meters.
• Orientation: Quaternion in w, x, y, z order.

Topic & Message Type

• Topic: /pose/left_hand, /pose/right_hand
• Message type: pose.LeftHandFrame, pose.RightHandFrame
• Encoding: protobuf

Left/right hand messages use pose_common: header plus 21 Transforms per hand. The i-th joint is transforms[i] (index 0–20). Same joint layout for both hands; the topic name indicates which hand.

Message definition (one message per frame per hand):

syntax = "proto3";

package pose;

import "common/header.proto";
import "pose/pose_common.proto";

message LeftHandFrame {
  .common.header.Header header = 1;
  repeated pose.common.Transform transforms = 2;
}

Transform type (from pose/pose_common.proto):

syntax = "proto3";

package pose.common;

message Quaternion {
  double w = 1;
  double x = 2;
  double y = 3;
  double z = 4;
}

message Transform {
  Quaternion quat = 1;
  double x = 2;
  double y = 3;
  double z = 4;
}

Joint Index and Conventions

21 joints per hand: wrist (0) plus five fingers with four joints each. Left-hand palm view below; right hand uses the same indices and connectivity.

Each joint is identified by index 0–20:

Index	Joint name
0	Wrist
1–4	Thumb CMC	Thumb MCP	Thumb IP	Thumb tip
5–8	Index MCP	Index PIP	Index DIP	Index tip
9–12	Middle MCP	Middle PIP	Middle DIP	Middle tip
13–16	Ring MCP	Ring PIP	Ring DIP	Ring tip
17–20	Pinky MCP	Pinky PIP	Pinky DIP	Pinky tip

Same joint layout for left and right; the topic name indicates which hand.