Opposition Thumb — Spherical Joint

Multi-Axial btGeneric6DofConstraint • 3D Reach Envelope • Ammo.js Physics • Prosthetic Design

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TM Joint (Trapeziometacarpal)

The saddle joint at the thumb base — primary source of opposition movement.

Flex/Ext 0°

Ab/Adduct 0°

MCP Joint (Metacarpophalangeal)

Condyloid joint at knuckle — flexion/extension + limited lateral motion.

Flex/Ext 0°

Ab/Adduct 0°

IP Joint (Interphalangeal)

Hinge joint at distal phalanx — single-axis flexion only.

Flex/Ext 0°

Current Angles

TM Flex

deg

TM Abd

deg

MCP Flex

deg

Pose Presets

Reach Envelope

Show envelope mesh

Show sample points

Show tip trail

Envelope Opacity 0.15

Envelope Resolution 24

Reachable Volume

Tip Trail

Opposition Thumb — Spherical Joint 3D

Verts: — • Tris: — • Envelope Vol: —

Joint Specifications

Metacarpal Length	—
Proximal Phalanx	—
Distal Phalanx	—
Total Thumb Length	—
TM DoF	2 axes
MCP DoF	2 axes
IP DoF	1 axis
Total DoF	5 axes

6-DoF Constraint Limits

TM Flex	-15° → 60°
TM Abd	-10° → 50°
MCP Flex	-10° → 80°
MCP Abd	-15° → 15°
IP Flex	0° → 80°

Physics State

Constraint Type	btGeneric6DofConstraint
Physics Bodies	—
Constraints	—
Sim Step	—

Envelope Statistics

Sample Points	—
Envelope Verts	—
Envelope Volume	—
Max Reach	—
Min Reach	—

Anatomy Reference

TM Joint (Saddle): Unique saddle-shaped joint at the base of the thumb. Allows flexion/extension and abduction/adduction, combining to produce opposition — the most important hand function.

MCP Joint (Condyloid): Elliptical joint at the knuckle. Primarily flexion/extension with limited lateral splay.

IP Joint (Hinge): Simple hinge at distal phalanx. Flexion only, for pinch force.

Reach Envelope: The 3D volume swept by the thumb tip through all achievable joint configurations. Critical for prosthetic design — determines what objects can be grasped.

Export

Ready. Adjust joint angles and explore the reach envelope.