While admittedly walk and run cycles do have some similarities, there are also some fundamental differences, and indeed challenges to be considered.
Speed:
With typically fewer frames in a run cycle than a walk (there are usually 12-16 frames per cycle for a run compared to 24 frames per cycle for a walk) , the speed of the run can highlight recurring problems when the animation is looped.
Air Time:
Unlike walking where at least one foot is in contact with the ground, termed air time, there is a point in a run when both feet are simultaneously off the ground where it’s important to maintain height in the hips, that the leading leg is stretched forward, the shoulders are high, the back curved to open up the chest, and with the head also held high, some drag applied.
Body Mechanics:
The posing is also more pushed in a run cycle than a walk. For example, making the centre of gravity different, and creating a sense of urgency and speed, the body leans forwards more during a run, and to show intention and determination, the arms usually pump harder with the elbows bent, the legs move more quickly, and the hands are often posed in a fist.
Overlap:
With running a much more purposeful action than walking and the character essentially pushing and pulling through space, additional overlap and a stricter approach to its application is required,
Once again, before creating my 3D run cycle, to allow me to better plan the keyframe positioning and the timing and spacing of my animation, I’d created a 2D version amalgamated with the Richard Williams’ run cycle template found in ‘The Animator’s Survival Kit’ (Williams, 2001), but unfortunately this time, when applied, the process didn’t translate well as I’d hoped into a 3D format.
Therefore, I instead based my regular run cycle on the model taken from Preston Blair’s book, ‘Cartoon Animation’ (Blair, 1994) which as can be seen below, covers a half-cycle (i.e. one step) which was then mirrored on the opposite side to complete the action. 
When setting the tempo, again as this was my first run cycle, I wanted to slow the animation down a little, just until I become more confident in my ability, and as I’d read in ‘The Animator’s Survival Kit’ how at least 3 frames are needed for the legs to cycle, I decided to work off a cycle of 18 frames, i.e. 9 frames for one step including a duplicate of the initial key frame to ensure that the animation looped properly.
The series of five video tutorials provided by Rachel at @rd3d_animation, which breaks the entire process down step-by-step proved extremely helpful (https://www.youtube.com/playlist?list=PL3-QyjKQWWaL43u9ViLbbFTXTykWriT2u) and as well as utilising the principle of animation I’d learned last year, learning from the mistakes I’d made in my walk cycles, this time when animating the arms, I was careful to ensure that the movement was more deliberate, to relay the purposeful nature of the run, and not floaty as in my initial zombie animation.
I also tried to create personality in my run, by making it feel more energetic, with higher knees and big arm swings which I feel suits the ‘Rain’ character, and to pay attention to detail by creating a more static hand posture and clenched fists, before checking that he feet also held correct interpolation values. Finally, to ensure that eye movement didn’t prove distracting during the run, I set the parent target in the eye rig to the head joint in the first frame, and once this was automatically transposed in the remaining frames, the character maintained eye contact throughout.
The Bio Motion Lab’s BML Runner, although an older version than the BML Walker asset that requires the installation and use of Flash Player Enabler, also proved helpful by providing a visual simulation of the run based on gender, which could then be rotated and viewed from different perspectives.
BML Runner Source: Biomotionlab.ca (https://www.biomotionlab.ca/bmlrunner/)
Also, with other animated resources good references, I studied the movement and the body mechanics in the run cycle below:
Source: YouTube, 2021
My first attempt at a regular run cycle can be seen here:
Regular Run – Front View
Regular Run – Side View
Tutor feedback was that I should add a curve to the back, and that the centre of gravity felt too far forward, which could be rectified by stretching the back to have it appear taller. The raised foot in the passing position should also point downward as it’s pulled forward and when airborne, and to create more enthusiastic movement and a more dynamic mid-air pose, the hips and feet could be positioned higher, which in turn would lead to a more dramatic drop. To also give more impact, just before the contact pose I could exaggerate the movement by lowering the front foot down even more, and raising the rear foot up even higher.
Side View – Frame 4
Side View – Frame 9
Side View – Frame 10
Taking these comments onboard I then amended my animation to achieve the following final result:
Front View
Perspective View
Side View
All in all, with this my first attempt at a run cycle, I’m happy with the result, but given the opportunity, I would mirror the determination and effort required when running in the character’s face by lowering the eyebrows, narrowing the eyes and creating a tight-lipped smile.
References:
Blair, P. (1994). Cartoon Animation. Tustin, California: Walter Foster Publishing, Inc.
Williams, R. E. (2001). The Animator’s Survival Kit. London: Faber and Faber. [online]. [Accessed 5 October 2024].
Available at: https://archive.org/details/TheAnimatorsSurvivalKitRichardWilliams
YouTube (2021). 3D Girl Cartoon Character – Run Cycle – Chris Z. [online]. [Accessed: 24 October 2024].