What happens when adding new vertices to weight painted mesh?

[Liramaril]

Hi, just wondering what happens here? I have been weight-painting a mesh and decided to experiment with adding vertices, which sometimes ends with them flying all over the place as soon as I plant them down. Does blender (which is what Im using) average all the vertices around it and apply that weight to it? is there any way to do that? Perhaps by hitting smooth? Im trying to figure out an easy way rather than selecting the new vertex and weighting it

[Quarrel Kukulcan]

1 hour ago, Liramaril said:

Does blender (which is what Im using) average all the vertices around it and apply that weight to it? is there any way to do that?

It depends how you add vertices.

If you extrude or duplicate, each new vertex gets the same weights as the one it was copied from. If you subdivide (including poking and inserting faces), Blender averages new vertex weights the way you mention. If you add a whole new cube or other basic Blender primitive, it will have no weights.

[Liramaril]

thanks! Super helpful!

[Ada Radius]

What Quarrel said. If you have added new verts, you can select them, select the verts of the area you want them in, more or less, and use the Smooth function. That plus painting with Blur might get you what you need without a lot of futzing. Be sure to re-normalize the weights (hit F9 to make sure the active group is getting normalized with the rest) - the Smooth tool doesn't seem to be normalizing after the smooth. It's awful on fingers. Pretty good otherwise.