Hello guys, I started to learn how to use Blender a couple of days ago. I’ve already created my character and I was able to put the rig on it, but I’ve been having problems posing since it gets some unwanted stretching and weird twists, then I found out that I should work on the weights of the bones. The problem is, when I click on certain bones, I can’t seem to be able to add or delete their weight of it. i.e. When I click on the main head’s bone, I can expand or limit the weight however I want, but I can’t do the same when I try to take the weight from the forearm of the upper arm (see image), no matter how much I click or drag on the spots I want to hit. Does anyone knows what the problem might be?
I would wonder if you have enough vertex density. Only vertices have weights, not faces, regardless of what Blender shows you-- it just blurs the colors out over the face. And vertices that are created by modifiers, like subdivision, can’t have individually painted weights.
Check, and try to toggling on/off certain Options on the 3D Viewport Header (on its “sub-Header” actually; it’s at the right end of that sub-Header, you might have to horizontally scroll to find Options; you may still find it on the Properties Editor.
The Options that I know, when activated, can sometimes “lock” your weight paint from working are: Auto Normalize and Restrict. But be careful if you toggle off Auto Normalize to fix a particular issue; remember to toggle it on right after, because it is often important to harmonize Weights from Vertexes when the latter are being shared by other Bones. Also, Restrict is very useful as an easy masking tool, so it’s often good to have it on, but not always.
Also, you should know there is actually a Paint Mask option in Weight Paint Mode, and it can be found at the begging of the Header from the 3D Viewport. It’s unlikely this is the problem, since it’s so easy to unmake the Face Mask selection; but since it’s a bit tricky, sometimes it might be confusing and cause some trouble; just ensure you have not accidentally Face Masked your mesh but, most essentially, that the Face Mask is toggled off. The same applies to Vertex Selection, which is right next to Face Mask.
Also, very important, make sure the Vertex Group from the Bone you’re on working on weight painting is not accidentally Locked, from the Properties Editor > Object Data Properties Tab > Vertex Groups.
