Animation Study - Walk cycle

Walk cycle animation study

Q-hyun Kim
Character Animator



  Walk cycle is very basic movement and foundation for further body mechanics but it's very hard.
I realized that there are a lot of principles and knowledge inside of walk cycle. Here is that thing I want to share.


  For animating walk cycle, we need to have five basic key poses like below.
(Rig from Animation Mentor)

[Pic #01]

[Pic #02]

  First, let's talk about translation of pelvis.
we need to see pelvis movement to analyze walk cycle since pelvis leads whole body mostly.
As pic #01, the pelvis part goes to lowest height at down pose and highest height at up pose and then these effect whole body height and we can check translation of left/right from front view. As you can see pic #02, the pelvis part starts to go to right on your side at down pose from center at contact pose for balance and keep moves a bit more at pass pose for cushion but it goes back to center at contact pose through up pose.


[Pic #03]

  Second, we have to understand rotation of pelvis for basic body mechanics. As you can see pic #03, the pelvis rotate left/right depending on legs. We have to think which leg of two the character uses for standing pose. For example, at contact pose of pic #03, this character is using right leg on his side. Newton's third law says that all forces between two objects exist in equal magnitude and opposite direction

FA = −FB  


  which means right leg of this character pushes ground and the ground pushes right hip simultaneously. This makes pelvis rotate like pic #03.  




  At down pose the character switches leg to left for supporting body, so pelvis rotates opposite side like above. After,  he is lifting his right leg to step further, which is pushing right part of pelvis and then it rotates opposite again. Next contact pose he drops his right leg to ground for step, which pulls right pelvis also down and pelvis rotate opposite again. 


  What about chest! 

  Human body is always trying to balance instinctively. Once human's pelvis, source of gravity, moves and rotates one side, chest needs to its job for balance. Yes! Twist! makes balance our body. As you can see the picture above, the chest line is trying to balance body by using twist. 

Let's see side view!



[Pic #04]


  Pelvis (Hip) is rotating up/down in this side view like pic #04. This character is walking forward and moving up/down at the same time and the pelvis needs to lead whole body as I said. Therefore, pelvis itself needs to have two forces to horizontal and vertical direction. Pelvis rotation helps body move those directions. At down pose, pelvis rotates up since body needs to move up. However pelvis needs to prepare movements in advance and it starts to rotate down from pass pose to help body move down and forward. Chest is twisting also for balance and those rotation make torso arc like red line of Pic #04.

  Those are what I studied. It seems quite simple but of course, there are more principles and physical science I haven't said. This is the very basic description I simplified. The video I put below is walk cycle test from the study. Thank you for reading!


video


Animation Study - Blinking Eye





BLINKING EYE
Animator Q

I am a character animator and also program director of 3dsense media school always looking for detail and delicate animation.
I will start looking eye-blinking animation deeper.
Here is the study for it.

First of all, we need to look over how real persons blink eyes. Here is the real footage.(#1)
video
#1

and now we will go over the way to analyse blinking.
First, as you can see an images below ( #2, and you can check animation #3 using #2), which I exported sequence images for that, we can check the spacing by drawing red line on upper eye lid. 
For the normal eye blinking, upper eye lid moves down fully in 3fr(from 1 to 4) having easy out and then eye closed at least 2fr having cushion( if you see fr num 4 and 5, the red line moves a bit down) and moves up fully in 4fr at least ( from 6 to 10) having easy in. 
Interesting thing is that the time to close eyes is faster than the time to open those. 
Overall, it happened within around 1 sec, if I put easy in/out.


#2

video
#3

Second thing is that, if you see eye lids carefully, you can see both eye lids moves inside to the center.
The below #4 is example.

#4

The black line is the shape of opened eye and the green line one is the one of closed.
As I analysed it, I could check the actual line moves inside and down- you can check line B. So we can guess that Muscles around eyes shrink inside like line C 
Additionally when eyes are closed fully, the upper lids push the skin of under lids and that makes A pulls out a bit.
For the eyebrows, when eyes are blinked, we could find out difference of the amount of movement of C and C'. In short, C is moving more amount than C'.

Final one is that skin has "viscosity'.

 " Viscosity is the quality that some liquids have of being thick and sticky."

So when we open eyes, each part of eye lids leave each other at different timing. If you think about one eye, tip part of the eye will depart each other later than center.

Also, Iris would get bigger when we close eyes and smaller vice versa because of dark/light adaptation.

So...here is the animation that I put my knowledge all together.


blink test from Q on Vimeo.





Thank you for watching!

by
Q