Forward Kinematics vs Inverse Kinematics

Drag the arm on each side. On the left you pose it joint-by-joint (FK). On the right you drag the hand and the joints solve themselves (IK).

Forward Kinematics (FK)

You pose the arm joint-by-joint. Rotate the shoulder and elbow controllers directly; the hand follows.

Shoulder θ₁: 0°
Elbow θ₂: 0°
FK: you choose the angles; the hand just ends up where those rotations put it.

Tip: drag the shoulder ring to swing the whole arm, then drag the elbow ring to fine-tune the pose.

Inverse Kinematics (IK)

You drag the controller. The shoulder and elbow solve themselves to reach the target while keeping bone lengths fixed.

Shoulder θ₁ (solved): 0°
Elbow θ₂ (solved): 0°
Reach: 0 / 0
IK: you choose a hand position; the system solves which angles will reach (or get closest).

Drag the dashed controller. Try moving beyond the arm's max reach to see it fully extend.