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peteb
03-17-2006, 12:27 PM
Ok I thought this was going to be a really simple thing to do but from what I've read on this forum it looks like its not possible which I find hard to believe.

I have a number of objects that make up a mechanical arm. None of these objects are aligned with world space simply because they're part of a bigger structer. So I moved the pivots for each joint into the the correct place (I'm not using bones). The pivot stays in line with world

So I go into Layout and rotate the pivot which seems to work in till I click out of rotate pivot mode to find that all rotation values are still set to World even if I select Local or parent.

From what I've read you have to use a null but I can't believe this. Surely the objects pivot can be aligned to the same rotation as what the object was created. And if not the question arises what the **** is the point of rotate pivot?



Pete B

Matt
03-17-2006, 12:48 PM
Setting up mechanical stuff like this is something I've always wished LW could do easier.

Giacomo99
03-17-2006, 03:23 PM
Hm. I feel your pain, but the fact is, if you don't use nulls or bones to set up a scene like this, you're just asking for trouble. That's more or less been true for every 3D program I've ever worked with-- pivot points are really, really unreliable in general.

That said, it sounds like you've discovered another interesting "feature" of Lightwave. The "retain 'World' values" thing sounds really obnoxious and I'm glad someone's warned me about it. Thanks.

GM

peteb
03-17-2006, 04:43 PM
Ha ha I've just read my post and love the way my use of the word H*ll has been
blanked as if it's a really bad word.

Anyway I think I'm going to have to go with bones then. I just think it's really weird how bones still descend from a pivot and yet they work fine.

Oh well I guess it's just the way it is?


Pete B

chikega
02-20-2013, 09:10 AM
I was doing my research on aligning pivot and came across this older thread. So if I understand correctly, is it best practice in mechanical rigging to parent, say a robot arm, to a null since the null can be aligned however?

RebelHill
02-20-2013, 09:14 AM
You can... though tbh its still simpler to just use bones and weights.

chikega
02-20-2013, 10:14 AM
Thanks for chiming in Craig. Do you know of any good tutorials for mechanical rigging using bones and weights?

RebelHill
02-20-2013, 10:22 AM
No different to "organic" rigging... the method is exactly the same. The only difference is that you explicitly give each bone its own weightmap that corresponds to a rigid part, and the give the corresponding part of the mesh 100% of that map and keep the map off all other parts.

chikega
02-20-2013, 02:06 PM
Thank you. I'll try that out.

lertola2
02-20-2013, 07:39 PM
Thanks for chiming in Craig. Do you know of any good tutorials for mechanical rigging using bones and weights?

For mechanical parts it is much easier and safer to put each part in its own layer and parent them to their bones. Making weight maps is tedious. And they they can make editing you object difficult.

lino.grandi
02-21-2013, 04:50 AM
There is one big advantage using bones and defined weight (in this case they would be really easy to define, since you don't need gradients): you can have your whole object in just one layer. That way would be super simple to cache the animation for example.
Of course it really depends on the complexity of the model.

The different approaches you may take are basically these:

1) You use a Hierarchy of Nulls and parent the separate layers to each null. Advantages: faster deformation, because there's no deformation at all, and no need for creating any weight.
2) You create a bone based rig and parent the separate Layers to each bone. This approach it's very similar to the first one, and you still don't have any deformation or weighting involved.
3) You create a bone based rig and use it to deform the object, that must have one weight defined for each individual part. Even if deformation it's involved, it should be really fast, because you have just one defined weight for each point. But if the object it's all in one layer (as it should be in this case), and it's really complex, you may have problems handling it if you need to make changes, since you have to identify the right layer among the others.

chikega
02-21-2013, 11:16 AM
Very helpful suggestions guys. It's interesting to see the different approaches as well as pros and cons of each. My animation isn't too complex. But since I'm mostly a 3d illustrator, the realm of animation is a bit foreign to me. I modeled this dental handpiece and have had a tough time trying to figure out how to get the pivot to align to the mandrel (bit). I'm not sure what the best practice is for something that is built at an angle. This is actually called a contra-angle handpiece in the dental field. I'm not sure if I should model every component that will be animated at the origin of world space, thus making sure the pivot is dead center, and then reposition the object within Layout. Or whether I should just model everything (using custom work planes) and then try to align the pivots later in Layout. In this case, I repositioned and aligned the Null in Layout best I could manually. But as you can see, it's still a little wobbly or not turning concentrically. What do you pro riggers do for more complex models? Is there a way of snapping the Null to the center and having it aligned perfectly? Thanks for any workflow hints. :)

111778

lino.grandi
02-21-2013, 11:31 AM
Yes.

If you're able to create in modeler two points exactly centered one at the base and the other to the tip of the mandrel, you're almost done.Then you can create a two points polygon, and transform it into a skelegon.

Then you can convert the skelegon into a bone in Layout....create a null, parent the null to the bone and set position and rotation to 0,0,0.

Then you can:

Unparent the Null and Rest the Rotation

or (better):

Unparent the Null, Clone it, and parent the New Null to the first one (the rotation of Null (2) will be right aligned then).

If you have problems, just send me the mandrel, and I'll do this for you (maybe recording a short video). ;)

lertola2
02-21-2013, 02:14 PM
I'm not sure if I should model every component that will be animated at the origin of world space, thus making sure the pivot is dead center, and then reposition the object within Layout. Or whether I should just model everything (using custom work planes) and then try to align the pivots later in Layout. In this case, I repositioned and aligned the Null in Layout best I could manually. But as you can see, it's still a little wobbly or not turning concentrically. What do you pro riggers do for more complex models? Is there a way of snapping the Null to the center and having it aligned perfectly? Thanks for any workflow hints. :)


111778

Definitely model everything in place. And while doing that create 2 point polygons that you can convert to skelegons. The skelegons will become the bones that you parent your parts to. No need to reposition or snap anything if you do it that way.

chikega
02-21-2013, 07:42 PM
These are great tips, guys. I'm going to try these out. And thank you so much Lino for offering to do a short video. I believe that a short video could also be useful for others who are newbies to mechanical rigging. I've researched for basic info on this topic. But I could only find a few obscure videos, but nothing very recent. Most are about organic characters which will prove to be useful soon. I purchased your rigging video and I hope to apply the knowledge to rigging and animating the dentition for teaching dental students.

CharlieL
03-01-2013, 02:45 PM
Thanks to all participants in this thread. I think this type of issues have been neglected for a long time.
Mechanical animation ought to be an interesting market for LW. I don't think it should be left to those
working with CAD software for construction only. We could have a greater role in this area.
Thanks especially to Lino Grandi for a well thought out work-flow and for sorting out available methods
for animation with their pros and cons.

As I so far mostly have worked with stills for technical illustration, these aspects on animation are very
interesting.

Thank you all!

SteveH
03-01-2013, 05:56 PM
I'd welcome a tutorial from Lino as well. I'm sure you're not busy right? ;-)
Maybe include a setup for a hydraulic cylinder and hinge setup like on a backhoe for instance?
That would be absolutely awesome.

Spinland
03-01-2013, 06:00 PM
In the meantime, this mechanical piston rig tutorial from William "Proton" Vaughan might help you along.

http://www.youtube.com/watch?v=p1EPcTeqeuc