For the curious, one extremely useful tool used for things like this is “inverse kinematics”[0] In this case you need the wrist, elbow, shoulder, hip, etc joint

For the curious, one extremely useful tool used for things like this is “inverse kinematics”[0] In this case you need the wrist, elbow, shoulder, hip, etc joints to bend such that the hand exactly reaches the door knob and stays on the knob as the door swings open possibly stepping the legs forward or backwards. Coding inverse kinematics from scratch is definitely non-trivial, luckily that is rarely necessary. https://en.wikipedia.org/wiki/Inverse_kinematics#Inverse_kinematics_and_3D_animation https://en.wikipedia.org/wiki/Inverse_kinematics#Inverse_kin...