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21 Dec 2016

Joint Breakdown: Shoulder Rotation Limits

Joint Breakdown: Shoulder Rotation Limits

Author:  Stephen   Categories:  Tutorials, Joint Breakdown  

Alright, cheat sheet #2 and we are continuing with the shoulder. That's the problem with these ball joints, so many directions to cover.

 

Creating Animation Cheat Sheets

Why did we create these cheat sheets, you ask? It all started many years ago when working on Thor; the rigs were so good it was impossible to create a bad pose! Pretty sweet. The reason for that though, was because all of the joints had limitations that prevented you from creating 'illegal' poses. 

As expected, problems arose when you needed to have a Frost Giant impacted by something (fighting, hit a wall, smash to the ground - typical things that Frost Giants do) but the joints would not physically rotate past a certain point. For that reason, we no longer think creating rotation limits are necessarily a good thing in rigs, even if posing becomes easier. Instead, we decided it was important to learn about the average range of motion for the human body so we could implement our own limitations within the animation and still have the full functionality of the rig to push the poses further as needed. That's how these cheat sheets came into existence; a reference guide so we don't forget. Still, huge thanks to the rigging department on Thor for teaching us the importance of proper range of motion.

 

Disclaimer: Rotation Limits Aren't Really Limits, So Says I

You've already seen the image at the top so maybe it's a little late for a disclaimer, but I feel like one probably needs to be included anyway. The one thing we need to remember when looking at joint rotation limitations is that these are mostly based on the average person and don't account for differences in body size or flexibility. These aren't hard, fast rules but rather guidelines that we use in our studio to try to keep our animation within a 'normal' range of motion. So can your character push beyond these limitations? Absolutely. Should you send me links to all of the amazing work you do where you ignore this reference and shove it in my face how wrong I am? Sure, why not. Send all hate mail to  victor@cgbreakdown.com (hehe, take that Victor!).

 

A couple of notes:
*We are trying to break the shoulder up into 'planes of rotation'. The first one covered the "Z-plane" (based on how the Hero character is loaded into Maya). This one focuses on the "X-plane" (side view) and "Y-plane" (top view).  
*We didn't really specify rotation values for the clavicle in the "Y-plane" images as we are instead concerned with the overall angle of the arm.
*The 140 degree rotation in the "Y-plane" is the best example where you will see a lot of variation based on the design of your character. An increase of fat and/or muscle in the chest can impact the total range of rotation.

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