I’m currently working on a 3D model of a steam gun-powered machine that features a continuous track system, similar to a tank or tracked vehicle. I would like to rig the track using bones and constraints (such as Follow Path or similar setups), without relying on Array or Curve modifiers.
I’ve been trying to set this up for a while now, but I haven’t been able to achieve a clean and reliable result so far. Honestly, I’m getting a bit desperate — I haven’t found any solid resources or tutorials online, and it seems like a fairly complex topic.
One important constraint is that I’m not building the track from scratch: I already have an existing model that I must work with, so I need a solution that adapts to and follows the current geometry, rather than recreating the system procedurally from zero.
Also, part of the rig is already done and working well: the wheels/sprockets are already rigged and driven by a functioning mechanism. What I need is for the track to move coherently with them, sliding correctly along the system as they rotate.
My goal is to:
Create a fully rigged track system driven by bones
Have the track follow a defined path smoothly
Use only constraints (no Array or Curve modifiers)
Adapt everything to an already existing model
Make the track properly sync and move with the already rigged wheels
I’m wondering what the best workflow or rigging approach would be to achieve this kind of setup under these limitations. Are there specific constraints, rig structures, or techniques that work best in this scenario?
I’m attaching some images of the track, I can’t upload any .blend file unfortunatly but if someone could reach me out would be nice. Thanks
There’s a method that uses a couple of curves, and Spline IK for the bone chain.
You will need quite a lot of bones to get the curves that you need. I think a bone for each ‘bump’ on the belt would do it. The bone could run across the bump, with the head and tail on the belt between the bumps.
It can also be done with geometry nodes calculating the bone positions, and the bones using the Geometry Attribute to get their positions from the geo-node setup.
I did a looping chain with a geo-node setup a little while ago. The nodes are more complicated than what you would need, as they also allow for the chain to be split as it animates.
That one’s gotta stay under wraps for now. But the core mechanic is in this simplified version.
I’ve just put together a simpler one that will address the needs of the original post. It has far fewer bones than will be needed for the actual belt model. It needs Blender v5 or higher to use Geometry Attribute bone constraint.
If you use that as your setup. I’d suggest creating your bones with a length of 1.0. They will be scaled by the Geometry Attribute constraint. Once it all lines up, you can set the Rest Pose for the bones from pose mode, and disable the Scale option in the constraint.
Hello, and thanks again for your reply! I really appreciate the example you shared, it’s been very helpful for understanding the approach.
I was already trying something similar to your first example and managed to get quite close, but I’m still missing a few key points. For now I’m focusing on the first setup (not the Geometry Nodes one, which feels a bit too complex for me at the moment).
Since this is not a tank track but more of a mechanical belt part, I made a couple of adjustments:
I unparented the main track mesh from the armature, so the chain bone can rotate without moving the entire object (no location changes).
I also created a custom curve from the main edge loop of the belt and used it as the spline target.
At the moment I’m running into two main issues:
With the Spline IK, when I assign the curve as target, the bones don’t follow the loop correctly. At a certain point they drift away from the curve instead of staying aligned, and I can’t figure out why.
When I parent the mesh to the armature, it breaks completely. The deformation looks wrong and the weight painting becomes very messy. This also happened in previous attempts, so I feel like I’m missing something fundamental.
Feel free to send the file over if you have somewhere to download it from. You can send a link in a private message.
If the setup is going to stay within Blender, then you could keep the belt as it’s own object, and lay it out flat. It will need to be the same length as the curve.
Then you can use the Curve Modifier on that belt mesh. Set the Deform Axis on the modifier to match the direction that the belt is pointing. Then when you animate the Belt object along that same axis, it will be rotated around the curve.
Keeping the relative Zero locations of the objects is important with the Curve Modifier. You can parent the belt mesh to the curve object, to keep them together. Otherwise things will fly apart when you move things around.
Yes, I understand. Unfortunately, I still need to move it and export it into the game engine, and I’m still having the other issues. I’ve shared the Drive link with the files here. Is that okay?
As an alternative to that, you can use Spline IK similar to the tank tracks.
The control curve is the path that the belt needs to follow. Another curve uses the Curve Modifier to follow that. The chain of bones uses Spline IK to follow this second curve. Moving the IK curve along it’s deform axis will have it rotate around the control curve.
You can Apply the Geometry Nodes modifier, then Convert to Curve on the mesh object. Make sure that the curve type is set to NURBS. That will give you a curve of the correct length to exactly follow the control curve. You can use that as the Spline IK target on the bone chain.
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