| kitler53 said:
so one joint has 3 axis for 3 points per joint? i'm confused as 20 x 3 = 60 points? can we track some joints with only 2 axis? i tried googling a few sources but everything seems to point back to the 20 joints thing. |
A functional joint in a 3D model rig (the underlying system that controls the mesh, or polygon geometry) is essentially 3 vertices or points structured in a hierarchal sequence (ex. hip joint, knee joint, ankle joint).
A joint in this particular sequence, say the knee, maintains a relation with the hip joint above and the ankle joint below (distance, which would represent the length of the femur or the length of the tibia/fibia, which stays constant). If you can envision the knee being the central pivot point, then the hip joint and the ankle joint would represent either ends of this basic joint chain.
The basic concept is that a joint isn't just a simple point floating in X,Y,Z space; it has to maintain its relation to the joint above and below in the chain. Additionally, that joint will have pre-determined restrictions (a knee joint for example can only pivot, and only on one plane, and not past full extension).
A simple joint layout could go something like: balls of feet (2) heels (2) ankles (2) knees (2) hips (2) spine (5) neck (1) clavicles (2) shoulders (2) elbows (2) wrists (2).
That's 24 joints right there with no hand/finger joints.
Even with an extremely limited spine (robot spine with 1 or 2 joints), one can see how there aren't enough joints for finger sensing as each hand will generally have about 15 joints.
