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Constraining about a roll


Gorf

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Hi, folks - Thanks for reading, sorry for such a basic question.

 

I'm modelling a mini servo with some attachments - the first is the "rotor" that attaches directly to the servo shaft, the second is an elbow piece and the third is an extended arm, as attached.

 

On the attached screen dump, I've photoshopped the bones of the different models in the choreography as best I can so they can all be seen. The dark red one at the bottom is the servo main bone. The big cyan one can be ignored - it's a boolean cutter. You can just about see the bone for the servo shaft - it's in there, but it's overlaid by the light red model bone of the rotor.

 

At the base of the elbow you can see its model bone. I haven't bothered to include the model bone for the arm.

 

When I roll the bone for the servo shaft, the "rotor" rolls correctly. How do I constrain the elbow bone so it rotates about that centre axis, keeping its place on the rotor? I don't want to do it by relocating the model bone, if possible, because I want to reuse the model and might need it to roll around a different centre point...

 

Hope I've explained myself properly...

 

edit: Sorry - should have mentioned the version. 12.0n

post-1449-1353884221_thumb.jpg

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I'm a bit confused... is this all one model or several models? True "model bones" are black so I'm guessing those purple bones are something you added?

Four models - the blue one, white one, and two "brass" ones.

 

The coloured ones are those that show up when I go into "bones" mode in the choreography. It's entirely possible I've got my nomenclature wrong. These things were all built from messing about with the primitives that are in the installed library.

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  • Hash Fellow

This would all be simpler if it were one model, but you can make constraint in a choreography or... you could make an Action for one model (the base) and import the others as action objects and do constraints in the Action.

 

A "Translate to" constraint would attache the elbow to the rotor. Turn on Compensate mode :compensate: after you pick the constraint but before you pick the target to keep the elbow from snapping to the center of the rotor.

 

A "Orient like" constraint will make it turn as the rotor turns.

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Thanks, Rob. I'll try those out and post my results.

 

I've done them as separate models because I'm going to be reusing several servos, arms, elbows etc. I realised when I started typing my original post that a model per servo would be easier, but I'd gone too far by then because I like to be economical where I can.

 

Incidentally, these are all to scale. The plan is to use the finished model as the basis for modelling a puppet around the contraption, which can then be printed in 3D, which will in turn be used to make a cast for a latex version to go over the real servo construction...

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Thanks, Rob. I'll try those out and post my results...

Yep - that did the trick, thanks. :) I needed to add a null for the translate constraint, but I worked that one out with little trouble.

 

It's so long since I did TAOAM I'd probably never have worked out the "compensate mode" thing.

untitled.avi

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Incidentally, these are all to scale. The plan is to use the finished model as the basis for modelling a puppet around the contraption, which can then be printed in 3D, which will in turn be used to make a cast for a latex version to go over the real servo construction...

 

That sounds like a cool project. Keep us posted.

 

 

 

It's so long since I did TAOAM I'd probably never have worked out the "compensate mode" thing.

 

If you ever upgrade, I'll note that "Compensate Mode" goes on by default now after you choose a constraint. And v17 also has an STL exporter. :)

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...And v17 also has an STL exporter. :)

I don't suppose it incorporates the bump map texture into its export? It would make life much easier...

 

the polygon exporters now have an "Apply displacement map to geometry" option.

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