This is my selected bone which should deform only painted part of mesh. But when I move it, it also move some other parts - nails of other leg as seen on second picture. This is not only case, some other bones also move some other parts of mesh which shouldn't be deformed by that bone. I checked weight painting and those nails aren't painted with this selected bone (DEF_Front_Leg.R.003). Maybe worth noticing - I was mirroring vertex groups, but this was appearing before that also. What could possibly be problem and fix
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2$\begingroup$ To make sure that a bone has zero weight, once in Weight Paint mode, go in the Viewport Overlays and enable Zero Weights > Active, if the vertex is not part of the group it will appear black. What you can do to remove some vertices from any group is select the vertices, go into the Vertex Group list, select the one from which you want to exclude, click on the down arrow to display the dropdown menu and choose Remove from All Groups $\endgroup$– moonbootsJun 30, 2021 at 10:21
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$\begingroup$ Thanks, didn't know about vertex group tip. Fixed :) $\endgroup$– RadoonJul 1, 2021 at 7:37
1 Answer
First, colors are not a good way to judge weights. You're not going to be able to see the difference between 0,0,1/255 blue and black. And if weights are even less than 1/255....
Second, realize that more bones than DEF_Front_Leg.003 are transforming. Everything parented to (or somehow constrained by) Front Leg.003 are also transforming. If your dog's left front nails are weighted slightly to the right foot or shin bone, then those bones are also moving.
When you have problems like this that look like weight problems, you should inspect a few vertices for their actual weights. Stay in weight paint mode, but switch to vertex select, and select a vertex that is deforming inappropriately (like a stretched vertex on the left nails.) Then open a sidebar and look on item/vertex weights. This will list all vertex groups to which the actively selected vertex belongs, along with their corresponding weights. You can use this to figure out which is the wrong bone to which it's weighted; you can see the group, even if it's a very small weight value.
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$\begingroup$ I found that one bone which should not have any weight on those nails somehow had a little bit. Probably because of automatic parenting. Thanks for advice, didn't know about vertex weights. $\endgroup$– RadoonJul 1, 2021 at 7:36
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$\begingroup$ Nathan, do you have any idea why Zero Weights > Active is not the default display mode in Weight Paint mode? Because I think it would make more sense than the current color spectrum where blue can be misunderstood as weight 0 when it may not be $\endgroup$ Jul 1, 2021 at 7:51
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$\begingroup$ @moonboots No idea, sorry. I don't think colors are a good way to judge weights anyways, other than as a rough, "hey, my weights for this bone are centered here"-- even beyond contrast issues with trying to display a 32 bit float as 8 bits of hue, there's the fact that weights can only be understood as a cohesive whole, not as individual groups. Best way to judge weights is to look at actual deforms. (Best way to judge weights, IMO, is to scale a bone about its center, without affecting its children, but that's not easy in Blender.) $\endgroup$– NathanJul 1, 2021 at 15:01
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