Universal joint

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Universal JointAuthor: Paul Smith
si-community user Grubber asked the board for a method of setting up a rig for a universal joint (For an explanation, see TechArtAndStuff UniversalJoints). User pooby promptly replied posting the scene file found below. Additional instructional screenshots provided by Hirazi Blue, see the linked thread below.

local backup: universal joint.scn

Issues concerning rigging & Face Robot...
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Grubber
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Joined: 22 Jun 2009, 21:11
Location: Vilnius, Lithuania

Universal joint

Post by Grubber » 09 Dec 2015, 11:20

Hi

I am trying to rig a universal joint. I found a tutorial on youtube for Maya, and I tried to apply it in Softimage without success. Anyone could help me to achieve the same results as in the tutorial?



Thank you.

Pooby
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Joined: 27 Aug 2010, 22:25

Re: Universal joint

Post by Pooby » 09 Dec 2015, 11:43

https://dl.dropboxusercontent.com/u/822 ... 0joint.scn

try this. It only works in one direction

Grubber
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Location: Vilnius, Lithuania

Re: Universal joint

Post by Grubber » 09 Dec 2015, 12:15

Thank you very much for such a quick solution!

Pooby
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Re: Universal joint

Post by Pooby » 09 Dec 2015, 13:06

Thats ok. Sorry I didn't label anything, but its not too complex and should be easy enough to pick apart.

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AceMastermind
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Re: Universal joint

Post by AceMastermind » 16 Dec 2015, 12:53

Cool, I can't open the scene in Mod Tool to check it out, can you post an image of the schematic view please? :)



EDIT
I'm not familiar with Maya but I assume Locators are the same as nulls in XSI and Aim constraints are the same as Direction constraints in XSI.

In the video he starts with 3 parts, the left part (input shaft), joint (journal cross) and right part (output shaft)

Then freezes the transforms which puts the center of each in the same position

Then he makes the journal cross a child of the input shaft

Then he creates 2 locators (nulls) and moves the upLocator (null1) to the side and the aimLocator (null2) behind the output shaft

Then he makes null1 a child of the input shaft as an upvector for the journal cross

Then direction constrains the journal cross to null2

and finally direction constrains the output shaft to null2

So far this all works when it rotates in place or when I move null2 up and down while not in motion, but the journal cross rotation breaks when trying to move null2 while the animation is playing.
I'm obviously messing up a step here and I think it has to do with the upvector not working properly.
Any help here is appreciated.


EDIT2
If someone would be so kind and load pooby's scene in Softimage and take a couple of screenshots of the objects in the viewport and schematic view so I can reproduce it in Mod Tool 7.5 that would be great! :)
Last edited by AceMastermind on 17 Dec 2015, 13:51, edited 1 time in total.

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Hirazi Blue
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Re: Universal joint

Post by Hirazi Blue » 16 Dec 2015, 13:54

In the attached file you'll find 3 screenshots, I hope they suffice to recreate the effect...
The object to the left is "cube", the object in the middle is "cube1" and the object to the right is "cube2".
Attachments
recreatethis.zip
(398.69 KiB) Downloaded 63 times
...

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Daniel Brassard
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Re: Universal joint

Post by Daniel Brassard » 16 Dec 2015, 14:23

A locator is a small icon like an x-y-z axis that marks a point in space (similar to Softimage Null icon). They are useful as a user interface for characters; for example, you can parent joints to the locator so moving the locator pushes and pulls the joint.

Attributes on the locator shape node allows you to change the locator’s local scale; that is, you can change the size of the locator (without affecting any objects that are parented or constrained to the locator). You can also use other shapes like a cube as a locator providing you disable it’s rendering.

A NULL in Maya is just an empty transform node (Same as a group node). Hitting crtl+g with nothing selected will create a null node which then has many purposes when rigging/animating. A null node (object) can also be create through: Create > Empty Group.

When you parent other objects under the null you can then transform them in a different coordinate space. The best way to understand how this works is to play around with it. It's a pretty fundamental rigging concept.

In Softimage, the Null is basically Maya locator and null rolled into one.
$ifndef "Softimage"
set "Softimage" "true"
$endif

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AceMastermind
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Re: Universal joint

Post by AceMastermind » 16 Dec 2015, 15:45

Awesome thanks for the images! :ymhug:
I assigned the upvector to the output shaft instead of the joint and now it works. :)

Heres what I got
UjointRig.PNG

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