>>271260287
VR games tend to take two different approaches to the player's body: They either have disembodied floating head+hands (Rec Room is an example of this) or they use complete avatar body and inverse kinematics to figure out where the skeleton is supposed to be. IK is software that works in reverse to determine how joints and limbs bend based on the end points, so it figures where your elbow is based on where you head and hand is and this means you don't have to track every single bone in your body.

VRChat uses IK for both standard VR 3 point tracking (knowing head and two hand positions from the headset and two controllers) and FBT (knowing the position of the player's head+hands+hips+two feet from the extra pucks)

In 3 point tracking it guesses where your entire lower body is based on your head and hand positions - so the IK will make your avatar crouch when you crouch but obviously its guesses won't match your feet positions and it will just sort of step about trying to keep your avatar's feet on the ground somewhere beneath your head in a way that looks natural. In FBT it doesn't have to guess much except for knees and stuff (which the IK will usually predict correctly if your proportions are the same)

VRChat's IK's is quite decent and most VR games can't do it well or don't even bother.