Universal Drive Shaft Max Boning.

oXYnary

Its another one of oXY's durr, its so obvious threads.

How do I create a bone structure for a universal/driveaxle in max? I mean so that the children only rotate in one axis. And... I want to do inverse k with it as well.

http://en.wikipedia.org/wiki/Universal_joint

I assume I need three bones, two as children. The third constrained for its axis between the other two (I can fake this if too much hassle - the mid section would never be seen easily with the angles.

Edit: Better be explicit. I need to attach it so it gets X movement from inverse kin from a master object. I dont need it to spin, just follow the movements correctly of suspension.

Mark Dygert

http://www.3dtotal.com/team/Tutorials_3/U_Joint_tutorial/u_joint_01.asp

You can replace the dummies with actual bones if you need to but the key is using the look at constraints. You can also play around with the settings for each bone in Hierarchy tab > IK

oXYnary

Auh! Thank you sir!

oXYnary

Ok Im getting lost in the process. Im probably trying to over analyze, but this is frustating the hell out of me. The tut relies on linking subobjects together which I cannot since it needs to be boned. It also assumes universals at both ends with a telescoping action. No. One universal with a dogbone (pin that slides in and out of the universal outdrive slot).

So you go up the chain from the axle to the differential. The issue well see, what about the steering? In other words, this isnt a straight line axle with suspension. It goes to a steering hub. (So think like fwd). When the steering hub turns, I need the axle to follow it , but the universal end to keep.


Root.

-suspension arm
--shock

--steering hub
---BoneA: Axle

---

BoneB: Dogbone/universal

So the axle is getting its movement and rotation from the steering hub. The problem is it would transfer that to BoneB, and even with a look at attachment, B will move in space versus in and out of the differential outdrive.


I could go (in attached file-Max 9) http://www.oxynary.com/downloads/example.zip


Root.

-BoneA: Dogbone/universal
--BoneB: Axle

-suspension arm
--shock
--steering hub


Again, similar issue since Im getting my movement from the end of the chain (ie a constraint from bone B to the axle). So the axle will move up and down, but not transfer the movement backwords to the universal/dogbone.


Is there a freebie model out there thats boned that I can look at to see how they made the boning structure and the constraints used? Its always much easier for me to actually see something.

oXYnary

Bump. I know this is a rigger question, and while I can weight vertices decent, creating bones from scratch I still suxors.

Mark Dygert

I played with your file, and came up with this, using wire parameters and a look at constraint. Click play in the max file or scrub the bar to see it in action (or look at the example avi). I'm pretty sure that's how you intended it to work?
http://www.vigville.com/forum_images/example01.zip (<-3dsmax 2009 file)
http://www.vigville.com/forum_images/UJointExample01.avi (<-example video)


Break Down:

• One bone is assigned the look at constraint and looks at the steering hub But the look at monopolizes the rotation controllers so we create...

• Another bone inside of that one (green bone). I copied the look-at bone and relinked it to be a child of the look-at (not the master bone). This new green bone is what you will skin to. Linking the bone like this leaves its rotation controllers open to input, but inherits the motion from the parent bone. This takes care of the up and down motion but now we need the green bone to spin along with the master bone.

• Using Main Menu > Animation > Wire Parameters I told the master parent bone's X rotation to control the green bones X rotation.

( I can go into greater detail on how the Wire Parameters menu works if you need me to, the help files explain it pretty well.)

This takes care of the rotation and everything works like it should, at least if I understand the needed motions...