The following suggestions produce best results for Auto-Skeleton and are generally useful, regardless of how you set up the solve.
- At the time Auto-Skeleton is run, the actor must be in a T- or A-pose.
- Legs must be in a natural, neutral stance:
- Feet must be about shoulder width apart.
- Feet must point forward (slightly out is OK, symmetry matters most).
- Feet must be in the same position forward and backward.
- Legs must be straight.
- Waist to head must be relaxed, natural, and straight.
- Feet, waist, chest, and head must all point forward. Prevent actors from standing with a slight twist if they're looking off to the side watching how to perform the ROM. Auto-Skeleton cannot tell if the head is not pointing straight ahead as opposed to the markers being placed inaccurately, so it assumes the head is straight.
- The root is assumed to be over the mid-foot, probably a little in front of the ankle. This is usually how people stand when relaxed. Prevent actors from standing too stiff and straight and leaning back, or putting too much effort into just standing and leaning forward.
- Arms must be straight.
- Fingers must be straight.
- Mid-segment markers (thigh, shin, bicep, and forarm) are ignored.
- Root position front-to-back and to some extent side-to-side works best when the waist markers are symmetric.
- Aim for the waist markers to be close to all the same height. Often back is higher than front, which is OK, but avoid extremes.
- Waist marker height overall is mostly ignored by Auto-Skeleton. Try to place waist markers well, but be aware that Auto-Skeleton assumes that waist marker height is not a reliable way to determine anything.
- Place the outer knee marker so that it's on the side of the knee joint and symmetric in placement for both legs (same height and middle of knee front-to-back on both left and right).
- Inner knee marker is ignored.
- Upper knee marker in the Production marker set is ignored.
- Place ankle markers as closely as possible to the ankle joint center, but note that Auto-Skeleton ignores their height.
- Ideally, MT markers should be at the same height and their midpoint defines where the toe joint ends up, as well as the height of the foot.
- Toe and heel should be centered and ideally at similar height.
- Place CLAV, STRN, C7 and T10 in the center of the body. Auto-Skeleton ignores their height, but partially uses them for actor-facing direction.
- Ensure that the front and back shoulder markers are symmetric left-to-right and front-to-back, and that a line from front-to-back is close to intersecting the shoulder joint center.
- Place the outer elbow markers on the sides of the joints.
- If present, place inner elbow markers on the side of the joint, symmetrically to the outer.
- Place wrist markers so that their midpoint defines the wrist joint center. Auto-Skeleton assumes this for both arm scale and arm posing, and correct wrist joint calibration is essential for the fingers to solve well.
- Head markers are ignored by Auto-Skeleton. It assumes that the actor is standing straight, with the head looking forward.
A- vs T-pose
Auto-Skeleton works with an A- or T-pose. The T-pose may give slightly better results because it assumes the clavicles are straight, whereas with an A-pose, it estimates the appropriate bend downward.
Single frame vs ROM
Auto-Skeleton looks only at the marker positions at the current frame. You need only a T- or A-pose to run it, but having a ROM present is useful to check whether the resulting calibration solves well.