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I am building a horizontal folding door with segments that open like a concertina. Method:

  • I first select the door segments then the armature.
  • Cntrl + P
  • "set parent to" / Armature deform/ with automatic weights
  • or with bones?? bones relative?? enter image description here The attachment works! But when I operate/ opens the armature the door segments are pushed skew and off centre from the bones. What am I doing wrong?

Any suggestions?

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  • $\begingroup$ you should go With Empty Groups, then assign vertices to the groups they are supposed to be part of. With Automatic Weight won't give a good result as there's a risk that a bone influences a part that it is not supposed to influence. But maybe share your file? $\endgroup$ – moonboots Jun 15 '20 at 12:11
  • $\begingroup$ Thank you for the advice, I will try it later...where can I upload my blend file if you want to check out my armature? The second problem is: when the armature is straight, the door segments edges are snug against each other, but when the armature starts to bend, the door segments are pulling away from each other. In real life you will never see this phenomenon....? $\endgroup$ – Barend Jun 15 '20 at 13:04
  • $\begingroup$ use blend-exchange.giantcowfilms.com $\endgroup$ – moonboots Jun 15 '20 at 13:16
  • $\begingroup$ The blender file can be downloaded here: blend-exchange.giantcowfilms.com/b/yJEvKKPP $\endgroup$ – Barend Jun 15 '20 at 14:50
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You could rig this sort of bus door arrangement without bones:

enter image description here

.. a series of hinges, each parented to the previous hinge.

Every hinge has its Z rotation driven by the zero'th, 'master' hinge.. ('Rot Master'). The odd-numbered hinges have -2 * the Z rotation of the master:

enter image description here

and the even-numbered hinges have +2 * the Z rotation of the master. The drivers can be cut-and-pasted; with care, pairs of doors can be duplicated along with their drivers.

The master's Z rotation is driven by the handle, thus:

enter image description here

.. where the '20' in the expression is the distance from the handle to the master when fully extended. The handle should have a Limit Location constraint to prevent it going off-axis, below 0, or beyond full extension.

The master and the handle can both be parented to a Root object (The big cube at the left) so the whole rig can be moved around. Doors, or whatever, can be parented to their respective hinges.

enter image description here

..sort of a cheap, limited, home-made IK.

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  • $\begingroup$ Good one for blender.stackexchange.com/questions/148088/trying-to-rig-a-map too $\endgroup$ – batFINGER Jun 15 '20 at 17:03
  • $\begingroup$ @batFINGER ..or that's a good one for this, with a couple of constraints to prevent the doors from going off the rails.. I like VeloFX's solution.. very general. I'd completely forgotten that question! $\endgroup$ – Robin Betts Jun 15 '20 at 17:07
  • $\begingroup$ Hi Robin, thank you for your idea of showing how to fold the door panels with hinges. 1. Can you tell me where do I access the hinge's driven property tab? 2. Why are the hinges and door "locked"? I want to attach real hinges to the door and modify the door panels. 3. I do not see any constraint setup, but only for the door handle? 4. Is the door hinge an empty cube? $\endgroup$ – Barend Jun 16 '20 at 13:07
  • $\begingroup$ @Barend Sorry, the linked .blend was locked off as if for an animator. I've replaced the link, it's now to an unlocked version. You still won't be able to rotate the hinges in Z though, because that axis is driven. The simplest way to see that is to N, open the properties panel of the 3D view > 'Item' tab, and have a look at the transforms of the objects You will see the Z rotation of the hinges is purple, showing it's driven. Right-click on the purple field, and select 'Open Drivers Editor'. You may have to move the edge of the Graph section of the panel to see the Driver Expression section. $\endgroup$ – Robin Betts Jun 16 '20 at 14:38
  • $\begingroup$ Hi Robin, regarding the rigging bus door project: Are the box hinges empty cubes? How do you hook up the doors to the hinges? Can I now parent 3d hinges to the cubes and parent the door panels to the 3d hinges? Please advise me if I am missing it. Many thanks. $\endgroup$ – Barend Jun 18 '20 at 20:58
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You must have somehow parented With Automatic Weight which has given to some bones influence on some doors that they are not supposed to control. So here is how you could fix the whole thing. First you could have joined all your doors together, but let keep them apart:

  • Disable the Lock Object Modes option, it will make the interaction between objects and bones easier.

enter image description here

  • Select the armature and enable the In Front option so that you can see it through the objects.

enter image description here

  • Select all the doors and AltP > Clear Parent to deparent them from the armature.

enter image description here

  • Put the Timeline cursor at 0 so that the armature is on its Rest position (I guess it's the case at frame 0). Select a door, Shift select the armature, switch it to Pose mode, select the bone of this door, press CtrlP > Bone.

enter image description here

  • It should work:

enter image description here

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  • $\begingroup$ Thank You Moonboots! It works exactly what I wanted to do. You are awesome! Thanks for rolling away this big mountain, I really appreciate all the trouble you took to make this clear, I would have sit stuck for hours trying to figure this out. God Bless you. $\endgroup$ – Barend Jun 15 '20 at 15:55

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