Run Cycle
Autor: Rodri Torres | Date: Agosto 2.005 | Translation: Francesco Campobasso | Revision: 0.4
This document explains how to create a run cycle using animation curves. The workflow can be used in any 3D software able to work with animation curves.
The axes mentioned in this document can vary depending on the software used. Although I have used Maya to do this tutorial, I have also shown the axes for 3d Studio Max.
The time (frames) used for this exercise are 20 (10 frames per stride). The time of the software should be adjusted to 24 fps (film).
We will be using 20 frames just to simplify the exercise, since the main poses will correspond to frames 0 – 5 – 10 – 15 – 20.
Introduction
I know of two main ways of animating cycles of any kind: posing and animating each body part independently.
This tutorial is based on the second one, animating each part of the body independently to create cycling movements.
If you have never animated a cycle like this, and if, as I was, you too are used to the pose to pose method, doing cycles this way can be a little strangee.
Once you understand the process of creating a cycle in this way the results are quite good.
It goes without saying that the author of this document hasn't developed this "technique" of creating cycles, which is well known by professional animators.
To complete this tutorial it is recommended having medium/high knowledge of the use of the animation curves.
RotateY in Maya). >> To Emiliano MartÃnez for the great italian translation. Thanks Emiliano!
Timing/Spacing.
Rough curve in TY. To achieve good timing you will likely need to key more frames creating little holds ...
We begin by animating the up and down movement of the hips on the corresponding axes. (TZ 3DsMax – TY Maya).
It's the most important aspect, and the part on which the whole cycle rests... just imagine that the hips are a bouncing ball that to give weight and rhythm to the cycle.
We should tweak the curve until we are satisfied with the appearance without killing yourself. Later, we will need to tweak this curve so that it better corresponds with the rest of the cycle.
The skates
Once we're satisfied with the hip motion we can go on to the feet. Just like it was a walk cycle...
This curve is the TZ of one foot. The other foot should have the same curve but in opposition (i.e., when one foot is forward the other foot is back).
... we animate the translation of the feet in TZ, or the one that corresponds to your animations software.
With a bit of imagination, when you finish this step, you should be able to see the rhythm of the cycle.
High Pose & Passing
At this point you should save your work. If we do something wrong, (Which is normal at when starting out), we can recover the work already done.
This next step can't be done with curves. We have to adjust "by hand" the poses. We have to create poses that look like the ones in the image and must be keyed in the shown frames.
The frames 0 – 10 – 20 are the ones where the character is in his High Pose, and just when he starts to fall.
The frames 5 – 15 are the Passing Poses, when the character slows down the fall and just before he starts going up.
Since we are only adjusting the shown frames (High Pose & Passing). It's important not forget what's happening in the other frames.
All of this is done by hand. Don't forget to key each pose.
Contact Pose
Now we have to tweak the pose where the character touches the ground (Contact).
We should tweak the hip's animation curve, so that the contact pose begins when the foot is just in front of the body. That is, depending on the curve, it can happen that the foot touches the ground a little bit late (that it is directly under the body).
This makes the cycle to look very weird.
Take a run up
The important thing now is that during at least one frame we can see the foot pushing the body up.
This must do by hand.
The simplest way to do that is just moving through the frames until you can find the one that gives us a straight leg if we rotate the foot to the ground.
Unfortunately, I don't know any may to make this process quick or easy. Just keep adjusting by hand until it looks good.
Finishing the legs
At this point we have to try to make some arcs in the legs trajectory when they go from rear to front.
Almost all of a human movements are in arcs/curves.
The image above shows an example of how the trajectory should look.
If we use “Show Trajectory” in Max, or “Motion Trail” in Maya, we might see some some straight lines. This is likely due to the lack of keys in the trajectory. There is no rule for this. So when trying to figure the right trajectory always look at the inertia of the legs and feet.
The feet
The most important thing now is that the feet show the weight that the leg is applying to them. This makes the inertia visible. The image below shows some rough poses of the rotation and translation of the feet...
The toes
The toes are an important step in any cycle, we should take care when animating them.
They give agility to the cycle, and stop the legs and feet from looking stiff.
Contact frames showing the movement of the foot to the ground. These are rough and just references for our purpose.
We should animate the toes throughout the cycle. Making them how we want depending on the foot pose.
The animation is driven by inertia. If the foot is moving forward, the toes should appear to slow down (rotated backwards)... If the foot goes down (like in the image), the toes are "dragged" by the foot. We should rotate them up.
The image above shows the contact pose of the foot with the ground.
The movement of the toes in relation the foot should be slower - they should overlap the foot movement. The number of frames can vary but it should be around 2 or 3 frames.
Arc movements of the feet
Right now the feet probably will have a straight trajectory when they leave the ground, this means that they come and go through the same path. Once again we have to avoid the straight movements, so the perfect thing to do is to take out the feet from the body in the passing pose.
The image below shows the arc that the foot should follow. Obviously when the foot is on the ground there has no side movement.
Top View
Rotating the feet to the outside
This point is really simple, during the whole animation you should rotate feet a little towards the outside. This is how most people run... You can of course rotate them inward if that's what you want.
Moving the feet out in the Passing Pose
It's possible that we have to rotate the feet even more to the outside during Passing so that the foot does not pass through the ground.
You can avoid having the foot pass through the ground in two ways:
- Lifting the leg to create more room.
- Rotating the foot even more.
More animation in the hips...
Right now the hips only have vertical motion (up and down); the rhythm.
To finish with this part of the character we'll have to animate a little more .
Left to be done...
* Translation from left to right side (TranslateX in Max and Maya).
The TX curve should looks like this ...
* Rotation from left to right side - ( RotateZ in Max) – (
* Left and Right Rotation Vertically - (RotateY in Max) – (RotateZ in Maya).
The spine
The whole spine animation is done through rotation. You have to animate all three axes (RX, RY, RZ).
* Forward and backward rotation - (RotateX in Max and Maya).
The more curved pose is the passing pose. The less curved one is in the high pose.
Once you have done the overlapping. The more and less curved poses will be a bit delayed in time.
* The left and right rotation vertically - (RotateY in Max) – (RotateZ in Maya).
* The left and right rotation horizontally - (RotateZ in Max) – (RotateY in Maya).
In this step and the previous step, the spine has to be adjusted "in parts". That is, the chest should rotate more than the lower parts. So it's important to have different rotations depending on which part you are animating (low-middle-high).
It's important to note that the rotation of the body always follows the forward foot.
The head
The head should be animated as an extension of the spine, and should therefore be rotated to follow the spine.
Generally the head has less movement than the spine. It's a common mistake to over-animate the head, and that will give a "crazy" look to the head...
Again we should look at body's inertia and fit the heads movement to the inertia of the body's movement.
In a simple run and walk cycles the head usually looks forward.
The head, just as with the spine, should be animated in all three rotation axes (RX, RY, RZ).
* Up and down rotation- (RotateX in Max and Maya).
It's best to begin by posing the head looking forward in the frames (0-5-10-15-20).
* Left and right rotation - (RotateY in Max) – (RotateZ in Maya).
* Left and right rotation - (RotateZ in Max) – (RotateY in Maya).
In the previous steps we are trying to make it so that the head remains looking forward, but without appearing rigid.
Another method that can produce better results is to key the frames at 0 – 10 – 20 (High Pose) so that the head looks just off of straight forward.
Ideally, we should be able to play with the head's animation curves to find result we want.
The arms
The arms are the easiest part to do. We will animate them in much the same that we animated the legs: starting with main poses.
We'll need only two poses to begin with:
Frame 0 and 20 : Pose 1
Frame 10 : Opposite to Pose 1
It's important that the arm's rotations are the similar in both poses. You can just copy the rotation values from an arm to the other.
The wrists initially should be posed as in the image above. In the front arm they are rotated a little up and inward. In the rear arm you have to rotate the wrist backwards and inward.
Overlap (of curves).
Though you could have already done this, overlapping the curves is something that you should probably do at the end for organizational reasons.
We have to overlap the curves in the spine, arms, and head to achieve a smooth and realist movement.
What we are trying to do in this step is have smooth transitions between each part of the body throughout the whole cycle.
Polish
It's possible that some parts need more attention. To polish we should try and improve the arc movements, and smooth the motion over the whole body by overlapping curves, and tweaking values.
The Last Review
At this point we should take another look at all the curves of our cycle to ensure that everything the way we want it.
It's not usual to forget to put a curve in cycle, smooth out a few keys or leave one out. At this point we should check everything - play the animation, examine the curves of each part, etc.
Remember to not render the frames 0 or 20, since these frames should be identical. If you don't do this then your run will appear to pause when it loops. You don't need to remove the key-frames, simply use the timeline to not show the first and last frames.
More Animation
In this document I have not included comments about other things we could/should animate to improve the cycle.
There are a lot of details that we could animate to improve, such as...
- Animating the face.
- Squash & stretch in the body and/or face.
- Animating the fingers.
- Animating the shoulders.
- Etc etc ...
Main differences between walk and run cycles
1.- In the walk cycles there is always one foot on the ground. Where as in a run cycles both feet are in the air a specific moments.
2.- The timing/spacing are different in the run cycle.
3.- In the run cycles the arms moves in a more energetic way (the most in cartoony cycles).
4.- The body leans forward in a run cycle.
Ref.: The Animator Survival Kit
Final notes
This will be of little to no use if all you do is follow the steps without thinking about and trying to understand what is important about each step, and why we doing each step.
The author of this document is open to any comment, critique or suggestion that anyone can give.
Special thanks to...
>> To my good friend Francesco Campobasso for this translation. Gracias mil :)
>> To Blake Withers by their contribution.
...all those that directly or indirectly has collaborated with writing this document.
...the Aniguild members for their contributions and comments.
...the DeathFall staff for the support and help.
...the team at ArsAnimación, without them, all this probably will not exists.
To Highend3d.com, 3demotions.com, 3dvf.com, 3d-station.com, 3dmaxer.dk, codepixel.com, maxarea.com, maxforumns.net, sinefx.com and other sites for their support.
