random patches showing up in Vertex Groups?

I’m rigging/skinning a naturalistic human model, which means a lot of bones and custom Vertex Groups. As I proceed through the bone set, painting weights and testing deformations, I’ve come to realize that on occasion, a totally random patch of vertices will show up in already-painted and cleaned Vertex Groups (VGs). For example, after painting on only facial VGs all day, I turned back to work on the upper arm weighting, only to find that many of the VGs I’d painted and cleaned for the face now have vertexes from the armpit include in them. And its the same set of “rogue” vertices in each case – no way I could have accidentally painted the exact same set very time. In fact, this “armpit” set showed up in VGs I haven’t worked on in many days.

I’ve been careful to make sure I use the “Vertex Group” constraint button while painting, to keep from spilling over the target VG. Plus I check each VG after completing it to make sure it’s clean, before checking deformation.

Before I report this as a bug (and wait apparently forever to have it addressed :(:mad: ), is it a known issue?

Most of the time people make mistakes painting ‘thru’ one VG onto another behind it. If this isn’t the case then I haven’t seen your particular problem discussed before.


How can you paint “through” a VG into another – that would require having two VGs active for painting at the same time, no? Can that even be done?

I frequently spill paint over my intended boundaries within one VG, that’s easy to clean up, or to limit the paint area using the “vertex Group” paint option.

But in this case, exactly the same set of vertices suddenly appeared as part of over a dozen different VGs, many of which I hadn’t been painting on for days, and were known to be clean when last worked on.

If the maybe-bug repeats itself, I’ll file a report (much good as that may do).

Spilling to me is someting that happens offen, and I never detect when I’m painting, just when for instance I move a arm and one vertex in the head also moves then I know that I have a spilling problem, and the worst is to find the vertex group that causes the problem…
…and no you don’t need to have 2 VG active to paint in another, its easy to try, wille painting the VG for the lowarm paint also some vertex of the foot, when you move the lowarm the foot vertex you’ve painted also move :slight_smile:
I’m not saying that in your case it isn’t a Bug, but Spilling hapens allot and without we know, but I think that now blender comes with a python script that tries to clean it automatic.
Keep it on.

Spilling doesn’t add vertices to another VG. It adds verts to the current VG (though they may be on an unwanted part of the mesh).

Example: In Edit Mode, specify two VGs, Top and Bottom. Assign a weight of 0.50 to each, then paint Top and spill some over into the area that has Bottom’s verts as well. Now check Bottom – the “spilled” verts aren’t painted to a different weight for Bottom.

A vertex Group isn’t just a collection vertices, it’s those vertices AND their weighting in relation to a bone. This is necessary since the same vert can belong to any number of VGs.

As far as detecting spills, it’s very easy to do outside of the Weight Paint Mode, just examine each VG by selecting it Edit mode. Even verts with extremely small or zero weight can then be seen, which is difficult to do in the painting mode. You can use the Remove tool to (duh) remove anything that isn’t s’posed to be there. I usually check this way after every session of painting. That’s how the “rogue” vertex patches showed up.

Sorry Chip, I wasn’t trying to solve your problem but just answering your question “is it a known issue?” Moderating means I have read every thread here at least once and I have a pretty good memory, so again, I don’t remember your specific problem being mentioned here before.

One caution though, if verts are added to a VG, with Subdivide or Knife or somesuch, after the original verts were assigned to that VG, then they may not be protected by the VGroup button in the paint tab. Like I said before though, it seems your problem is not caused by spilling. And “painting thru” usually only happens when you paint a new VG onto a Bone in Pose mode. Do you perhaps have a bone selected in Pose mode while painting another VG?


No 'pologies necessary, I can use any help I can get :smiley:

Your question may have fingered the issue. My Weight Painting (WP) procedure usually involves working on the model while posed, and yes, there’s often a bone selected that I’m not painting to. I’ve found you have to be in Pose Mode before going to WP mode to be able to R-click a bone for painting. Otherwise you have to select the VG from the Buttons panel list (annoyingly slow) or switch back & forth between Object, Pose and WP modes (even slower!). So I may start on the bone selected in Pose Mode, but then move to associated bones by R-clicking them in WP mode. The first bone stays “selected” (highlighted), but the VG for the right-clicked bone is enabled for painting.

If this is a source of probs, it may contribute, though how it could cause the same set of verts to be added to a double-handful of VGs is vertex voodoo to me :eek:

I’ll watch out for this set of circumstances and see if there’s any apparent correlation. So far today, the problem has yet to re-occur (crosses fingers and many toes as well).

EDIT: Actually, choosing a VG from the list is what leads to painting a VG while a different bone’s selected – been workin’ on this thing too long, got all muddled.

A half-dozen rogue patches showed up again after this last WP session – only possible clue I can see is that it seems to affect VGs that are adjacent to one another in the drop-down list (but not necessarily adjacent on the mesh), in groups of three or four.