Binding and weighting geo
What is skinning?
Skinning is the process of connecting geometry to the joints and then weighting the fall off. In terms of Maya we are connecting joints to vertices using a skin cluster node. The skin cluster node is part of the deformer family.
Binding : (Max) influences
When you bind any vertex will inherit a shared connection (weighting) to any number of joints (to a maximum set in the options).
Initial binding options: Post weights vs interactive weights
Interactive Weights
In post weights, the shared relationship between a vertex & any number of joints adds up to 1 (100%). Cannot drop under a value of 1 in total
Post Weights
In interactive weights, each joint can influence any vertex up to a value of 1 (100% each). The total value cannot drop under 1
After you edit the wights using painting weights which is a process of changing those relationships
The golden rules / common pitfalls
In skinning you never subtract you always add.
Edit weights manually, and then brush paint’ if necessary.
Don’t use smooth without ‘locking weights’.
Corrective blend shapes are added to maintain volume and create distinctive shapes within a deformation. However, the goal is to paint the weights as best as possible first, not to rely on the shape to ‘fix’ any skinning issues
In the bind skin option box the “bind to option” with joint hierarchy maya is going to bind all the joints in chain to the geometry
– Creating a broken bind
- Clean-up
I fist loaded all the weight to the chest and after I am going to remove it gradually to the right joint by floating the weight to the vertices of the corresponding joint. (by selecting the vertices in loops and the designated joint and flooding) chest-shoulder-elbow-wrist-fingers-clavical-lombars-pelvis
Grow selection to select vertices for the vertices
– Mirroring weights
after I passed on the leg following the same process (pelvis-hip-knee-ankle) and mirroring the weight on the other leg
for the feet I first edited the weight for one foot and after to mirror it to the other one I have select them both and mirrored the weight
Add influence to add a joint
Blending weights using component selections
– Pose space (corrective blend shape) deformers for corrections: adding a pose interpolator by going to a frame where the character’s skin is deforming incorrectly, or move the character into a pose where you want to add a corrective shape.
So I have created a pose and a modelling a shape to blend weights where the character geo would bend to make those poses more natural.
For the fingers in order for them to fold correctly I have added weight first to the joint that drove the movement, the joint that was the parent to the one where the geometry was bending unnaturally.
So I have selected the loop and converted to vertices and added the weight so that the influence of the geometry is shared between the two joints and the geometry folds more naturally
I have applied the same process to the consequent joint to share the influence on the geometry.
Average the weights based upon its neighbours
I after manually smoothed the paint weight for the thumb adding some influence to hold back the area where the thumb bend to maintain the volume
For the wrist I have applied the same process for the wrist selecting the vertices from an edge loop and add the influence to either the wrist joint or the elbow to maintain the volume when it’s bent.
Same for the elbow I have distributed the weight between the elbow and the shoulder by selecting the vertices of the mesh involved in the bend
For the shoulder the influences this time had to be distributed between three joints: the shoulder, the clavicle and the chest according to the the different parts of the shoulder itself.
The part on the top had to be blended for the shoulder and some weights added on the clavicle, the part corresponding to the armpit had to be shared between the clavicle and the chest always working according the vertices which in this case were only those affecting the specific are not the whole edge loop.
The most tedious part to skin weight is the spine since that the weight had to be distributed in a way that when the spine ben on a side the volume is maintained but if the influence on the pelvis was excessive the movement of the latter could have been compromised.
I have mirrored the skin weights from one arm to the other and from one leg to the other since I have been working on one side only.