Skinning volume preservation

by Cyberika posted 149 days ago | 9 comments

So guys what is your workflow doing volume preservation? I mean knees, elbow and most important clavicle, shoulderand buttocks.

by HashixC posted 118 days ago

Like most of you I use smart joint which push when the arm is bended (The smart joints are controlled by a drivenKey).

The cons of using corrective blenshape is when you have a cartoony character and the animators are tearing apart the rig (scaling + translate + rotate on most of the controls) Then you can't drive your blendshapes even with RBF.

by hazmondo posted 139 days ago

Judd Simantov used to have a really good video on his Game Character Academy website which demonstrated how to setup smart joints, unfortunately the website no longer exists except for an archived version from 2014 which doesn't contain the video, the video was called "Introduction to Rigging: Arm Deformations Part 3", maybe you could contact him and ask the to see it.

Another nice trick it to play with the positions of the ribbon controls, assuming you have ribbons setup for the upper and lower parts of your arms and legs, you can drive the positions of the controls based on rotation/angle of the elbow and knee. For example, if you have a ribbon on the lower arm it will attach to the elbow and wrist, when you bend your arm you can translate the elbow attach point towards the wrist, this avoids a lot of intersections and combined with some DQ blend weighting can give excellent results even without correctives and if you want to implement correctives it's easier to sculpt them because there's less intersections :)

by denilson020898 posted 139 days ago

Great, I wouldn't have thought about that. I always rely on corrective blendshape to do that, which is a pain.

Haven't played with blended weight yet. But it seems I only need to paint DQ only on cumbersome areas.

by Zolla posted 146 days ago

My version of 'smart' joints have some initial offset from the child's pivot and has parameters to weight the rotation from 0 to 1 (from parent to child) on each axis. So with this offset it can be mirrored and with these parameters it can be tweaked after skinning. On average cases it works well for non-hero characters.

Labelling joints can also give a clue on mirroring, copying.

(These joints can be driven by math nodes or driven keys.)

by Cyberika posted 146 days ago

Thanks guys! I’m using only DQ. But some times, if character type is cartoony and animator is forcing the pose it breaks the volume. Corrective shapes are time consuming. Can you give me some clue or doc’s links about “smart joints” rotation?

by hazmondo posted 146 days ago

Corrective sculpts are difficult to beat because they're easy to create and very art directable, the only thing you have to figure out is how to active them, it's fine to activate an elbow or knee corrective with a rotation axis if you choose the a good rotation order but areas like the shoulder and hips are harder. In newer versions of Maya you have the Pose Editor, I don't know what type of interpolation it uses but radial basis functions (RBF) are a popular type of interpolation in the community but they can be tricky to understand at first. Obviously if your working in a game engine then you'll want to primarily use joints but you can still use RBF interpolation to drive them.

by vshotarov posted 146 days ago

Yeah, I'd say similar to Zolla, but I never add inbetween joints with 50% rotations, just because I am not fond of the workflow when painting and mirroring the skin weights with them.

In fast paced productions I rely entirely on DQ and, to be honest, it does seem to give me about 90% of the preservation I need (of course, it does occasionally cause other issues). If I have the time, I'd put in the extra 10% as blendshapes.

Im too curious to see any clever solutions, though!

by Zolla posted 147 days ago

Hi Cyberika! Most of the times I'm using angle driven "smart joints", rotating half way with the child joint and pushes out if it bends. Sometimes I just paint on some weighted dual quaternion of the skin deformer. Pose based blendshapes are the lasts I would use. Not so fast in action but gives nice result if you can sculpt with correct anatomy. Anyone has another solution?