I have a requirement to rotate part of an object, leaving other area intact, so have created a bone and defined the vertices belonging to the bone. Since the part to be rotated is very sharply delineated I am using manual vertex assignment. However, when the the part is deformed some portion of another part of the object is also getting deformed, which is not desired. I tried setting the paints in the weight paint mode, but here also the brush either includes the unwanted portion or subtracts from the part itself. A related query is: I have seen highlighted lines extending from vertices to neighboring vertices, that seem to be indicating weights (or influences? not sure... I am new to blender). What's the logic of applying these weights and is there a way to change them? They are sometimes seemingly arbitrary. In the attached figure for example, A influences B and F but not C. Why? And how, if at all, to change this influencing?Undesired deform behaviorVertex influencing, how to change the default behavior?

  • $\begingroup$ For "mechanical" models that do not deform each piece, you could even avoid weighting altogether, separate the pieces into their own objects and parent each piece directly to its parent bone. $\endgroup$ – HENDRIX Oct 14 '17 at 18:18
  • $\begingroup$ Yes, eventually that's what I may have to do. $\endgroup$ – vierzig Oct 19 '17 at 8:47

I found a workaround: 1) In edit mode, select the vertex group assigned to the bone and hit P to separate the selection from the main object 2) remove the vertices from the main object that belong to the bone (there's actually just one in this case) 3) In object mode select the main object and the separated one and hit ctrl-J in order to join them. Now if I select the vertex at the tip of the part to be moved, there is no influence shown to the main part vertices. Maybe there is a double vertex at that position, but that doesn't create any problem for me for now. enter image description here

  • $\begingroup$ Interesting! I don't know why that works, but I'm glad it does. (: $\endgroup$ – SilverWolf Oct 22 '17 at 12:00
  • $\begingroup$ yeah :) Maybe, I'm doing too many wrong things, which cancel each other and in the end there's left something that is close to the right :)) $\endgroup$ – vierzig Oct 24 '17 at 5:39

You don't actually need to use Weight Paint to change the bone influence. Try this:

  • Find the vertex group you've been modifying in the Mesh tab of the Properties panel. (It'll probably be named after the bone.)
  • Select all the vertices and hit Remove.
  • Select only the ones you want the bone to move, and hit Assign.

You can see which groups the active vertex belongs to in the N panel, under Vertex Weights, and can edit them manually if necessary.

  • $\begingroup$ Whoops, hit the post button by accident. More coming... $\endgroup$ – SilverWolf Oct 14 '17 at 18:14
  • $\begingroup$ Actually, I am not using automatic weights but defining vertex group of the bone manually as shown in the first diagram (the highlighted vertices were added manually to the bone vertex group). The more interesting problem though, is the one related to default assignment of influences. How is it determined? It is certainly not based just on the distance between the vertices as can be seen clearly in diagram 3. $\endgroup$ – vierzig Oct 19 '17 at 8:51
  • $\begingroup$ Hm. Well, if you're doing manual assignment, it should work. I wonder what's going wrong. I think the default assignment is based on the distance from the bone--you can switch your bone view to Envelope to see this. $\endgroup$ – SilverWolf Oct 19 '17 at 13:37
  • $\begingroup$ Are there any other vertices in that vertex group, and are those selected vertices part of any other groups? $\endgroup$ – SilverWolf Oct 19 '17 at 13:38
  • $\begingroup$ No, there are no other vertices in the group. I have double-checked that. I also removed the double vertices. Thanks for your responses btw. I found a work-around that I am describing below. $\endgroup$ – vierzig Oct 22 '17 at 5:41

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