About bones, what breaks them and how to fix them

Bones are good tool and can be very useful and I had some success using them: Practice artwork - #13 by Majkel
But they’re definitely a learning curve and can be so frustrating to work with, I don’t know why but bones can be so broken, it might be just me specifically or other people also might have these problems. I made tests using Synfig 1.5.1-2021.10.21-linux64 and I will update this post with time as I find new bugs.
Anyway

1. GROUP TRANSFORMATION

Here is how bones should work, the blue lines on hand show bones where they actually are. This hand looks pretty good
bones-normal
Now here we see it being broken as hell
bone-broken
This might happen while trying to link vertices inside group to bones, skeleton has to be outside of said group for this to happen
Screenshot_20241006_072222
What breaks bones is transforming group hand in any way. Modifying anything

  • Origin
  • Offset
  • Angle
  • (Didn’t test but Skew angle probably too)
  • Scale

Will cause broken bones, if your bones suddenly get broken don’t fear because there’s fix to that (most likely). Simply set group parameters to original values i.e. Origin, Offset, Angle and Skew angle to 0 and Scale to 1, then you select all child layers in group and move/scale/rotate them to where they need to be.

However it might not work, in project I’m working on I copied leg group and moved it, when bones were broken I set group to default values, moved child layers to where they need to be and bones were still broken AND I DON’T KNOW WHY (EDIT: there was group scaling I didn’t notice).

2. COPYING GROUPS

While having character chopped into groups it is tempting to just copy groups for ease like I did with Orange:

There is head, neck, main body, tail etc. Being lazy I duplicated legs on left side of her body and just changed Z depth, similarly with wing, I made 1 wing and just duplicated it then added bones and everything works and is dandy.
Problem appears when I want second dragon but don’t want to do bones all over again so I duplicate with rigged bones.

There are 2 connected problems that appear simultaneously, first one is (not so) random parts detaching from bones

2nd problem: wtf happened here?
Screenshot_20241009_002709
On top of wing detaching from bones it also looks like this


It does look scary but solution is simple. Turns out few bones are named the same

Screenshot_20241011_042335
In red frame there are bones from wing (bone 28, 29 and 31) while in blue frame there are leg bones (bone 28, 29 and 30). So obviously having the same name for bones causes problem when duplicating rigged model and solution is to change bone names to something unique before duplicating.
Honestly I don’t even know how this happened in the first place, prevention method would be not being lazy with naming bones but I didn’t want to just change names of 37 bones.

I’m writing this in hopes it will help someone who encounters this problem because it took me so much itme to figure this out. If skeleton layer is inside group that is modified then it works as intended.

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I am rigging a new character here and i’ve got some serious problems. when i link parts of my character to their respective bones and move those bones, some of those parts are not moving in the desired manner. some are moving all over the place. what could be the problem?

Hard to tell from just short description, does it look similar to first problem? In such case check if there’s any transformation of a group

I thought transformation was the issue so i tried creating a simple rig to test, but im getting the same problem. check this out
synfig bones problem

Here is the original rig i am trying to construct

I managed to reproduce problem but only when I linked origin of layer to skeleton and I assume you did the same thing.
You need to select all vertices (either by selecting layer and clicking ctrl+A or selecting layer and clicking and dragging box over them) and then linking selected vertices (not origin) to the bone

Oh thank you very much.Solved!! You’re a lifesaver

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