ALT This seat system is designed to be much much better than the seat system found in VRChat. It theoretically can allow for any character to fit to the seat, and have them line up properly, with their knees over the edge.

ALT The surface of the seat is defined with 3 control points for the back, knee, and foot positions, and a spine angle, which collectively define the surface of the seat. This is much better than a single transform, since it provides enough information to calculate how to fit any sized avatar to a seat, whether the character is tiny or huge. Similarly, the same applies for really big seats or really small seats.

ALT When a character's legs are shorter than the available space on the seat, the back and foot IK positions will move forward or up, respectively, to keep the knees aligned with the seat. When a character's legs are longer than the available space on the seat, the knees will be moved instead to make room. If a character's upper leg is shorter, the knees will be moved forward. If a character's lower leg is shorter, the knees will be moved upward. If both happen, the knees will be moved both up and forward.

ALT The control points do not have to exist at 90 degree angles to each other. You can change the relative angles any amount and the legs will bend in response. For example, if you want to kick back, just move the foot control point forward a bit. You can also adjust the spine angle if you want the character sitting on the seat to lean back. At the extreme, you can even make the character sit in a way that is almost entirely laying down, or almost entirely standing up (as long as the control points are NOT perfectly collinear).