Skin weight problem!

IRMossimo

Hey all,
first time posting
so ive got a problem where im painting skin weights in certain areas of the character but also removes skin weight in different joint. Example while painting weights on spine_1 it removes skin weight in spine_2, so when i try to fix spine_2 spine_1 weights gets remove. Does anyone know what the problem is or know how to fix it?

thanks.

Edit; The program im using is MayaLT 16 extension 3 and the bind method im using is geodesic voxel. 

Eric Chadwick

It helps to specify which software you're using, including the version number, and exactly which weighting method you're using. What research have you done already? Indicating this will help others help you better. A screenshot of your setup might also help.

claydough

Are you painting a subtraction instead of painting addition? Geodesic voxel is just the method to calculate the initial bind so you are still weighting a smooth bind.
( subtraction will adjust weights in other joints to equal the smooth bind. Remember a smooth bind is smooth because deformation is spread across multiple joints )
Every paint operation's resulting value therefore is going to effect another weight's value.
The sum of any vtx's joint influence will always equal 1
( unless there is some new tech wizardry introduced in Maya unbeknownst to me as of yet? )
The only interactive predictable result you can get/see is by painting a deformation's additional influence.
subtracting a joints influence value from a vtx spends that value on another joint to equal 1.
Which will probably result in unwanted deformations when that "other" joint is rotated.

The way I try to think of it without confusing my easily confused mind is that you can "add" correct influence that you can see which will not then "add" incorrect influence you'll see later.
But subtracting "correct" influence behavior will "add"/spend to equal 1, an equal amount of incorrect behavior you likely see somewhere else.

Last I heard...
smoothing will cause the same unwanted behavior as subtraction. ( and if not smooth painting anymore I would still be surprised if flood smoothing was anything but problematic! )

Hope that helps ( is what was causing your other values change )
Instead of just confusing matters. But You were complaining about losing weight influences elsewhere not values being added upon elsewhere, so I am skeptical?
Does the loss actually result in unwanted/unpredictable deformation or a loss of wanted deformation?

Adding the screen shots as Eric suggested was a good idea. But your model in a neutral t-pose doesn't show how the result of the weight lost, negatively impacts resulting deformations.
You should show representative joint rotations that expose the problem to the deformation's end result.
Are you painting in a "posed/rotated" state so that you can see the effect a joints influence has on deformation while you are painting?

Did you already know about the paint by "addition only" strategy/rule of thumb?

IRMossimo

Since im still learning how to paint skin weights from what i can tell im adding values to the joints and not subtracting. The only tools ive been using is replace, add and smooth and for values 0 and 1. As you can see when i try to fix the left_arm i lose weight from the left_shoulder. So when i try to to fix the left_arm i lose values from left_shoulder. This goes for the whole thing when i try to paint/fix different part of the character, i never used to have this problem when i did skinning with maya13-15.

antweiler

Could it be a problem with weight locking?

When you use anything other than "add", maya needs to distribute weights you remove from a joint to other joints. In this case you need to carefully look into the weight locking of the joints, which prevents that weights are put to these joints. So in my case when i use smooth, i take care that most joints outside the paint area are locked.

I also recommend the solid brush, much more precise.