An animation is a series of frames. In step mode, animators focus on "key poses" or keyframes, capturing important moments of positions. In this mode, animations do not transition smoothly from one frame to another. Instead, they jump from one key position to the next. The in-between frames are left unrefined or omitted entirely.
This approach allows animators to clearly define the most crucial moments of movement or expression without the distraction of constant fluidity.
For example, consider a character preparing to jump. In step mode, the key poses would include a crouch, a jump, and a landing.
In contrast to stepped animation, spline mode involves smooth transitions between poses, with in-betweens generated automatically via interpolation. Spline animation is production-ready and used for final animations.
Why Stepped Animation
Step mode allows animators to overview an action and its pacing before committing to more detailed work.
Key poses are the most important elements of a movement. By concentrating on these keyframes, animators can simplify their workflow to focus on the most impactful actions. There is no transition between keyframes, so when you hit play, the software displays each pose sequentially as if flipping through a series of drawings before diving into more complex inbetweening to smoothen the animation.
Stepped animation also helps develop a basic sense of timing: with clear keyframes, you can easily test how long each pose is held and the rhythm of the overall animation. This method allows for quick iterations: if a pose feels too slow or fast, you can adjust the timing parameters without worrying about how it affects the in-betweens.
1. Key Frames
Animators begin by deciding the action's starting point and endpoint―the initial and final keyframes. For example, if you were animating a character that waves, you might start with the arm down and end with the arm fully raised.
We would then use your animation software to create keyframes at these points. Most programs allow the precise specification of frame numbers to provide clarity in the editing timeline.
It's important to control the timing between keyframes to achieve the desired movement. The time between keyframes is crucial: if a character snaps their fingers, you can space the frames close to give a sense of a sudden movement or further apart to emphasize it.
After placing keyframes, we usually play back the animation until it feels right, looking for any unintended motions or inefficiencies in timing.
While the focus of step mode is on the keyframes that define distinct movements, subtle adjustments in the poses can add depth. You can, for example, consider incorporating slight anticipations or follow-through animations at certain keyframes for better results.
If you take a bouncing ball as an example, you could end up with something like this:
- Key Frame 1: The ball is at its highest point.
- Key Frame 2: The ball is halfway down to the ground.
- Key Frame 3: The ball touches the ground.
- Key Frame 4: The ball is at its lowest point (compressed).
- Key Frame 5: The ball returns to the initial height.
2. Storyboarding & Animatic
The selected keyframes are used during pre-production for storyboards and animatics.
Storyboarding is creating a visual representation of a sequence of actions or events in the form of a series of images arranged in the order they will appear. It's a blueprint to plan scenes, transitions, and key actions before moving into the animation phase.
A storyboard clarifies the sequence of keyframes for stepped animation.
An animatic is a preliminary version of an animation combining static images from storyboards with a timeline, sound, and sometimes voiceover to offer a clearer vision of how the story unfolds.
Both help avoid costly revisions during later stages of production, providing a structure that simplifies the decision-making process for animators. This is particularly important in stepped animation―where there are no transitions between poses―to understand how these keyframes relate to one another.
3. Switching To Spline Mode
As animators begin production, spline mode will slowly replace step mode.
The main challenge when working with stepped animation is getting a feel of how timing will translate into the final rendered movement.
When you switch from stepped to spline, the interpolation creates a smoother movement that may not have the desired energy. While your brain can fill in the gaps during the stepped stage, the computer's interpolation can create a smoother but less impactful motion. If a character jumps, the snappy ascent created in stepped mode can become a lagging glide with interpolation.
For this reason, it's important to frequently switch between spline and step mode during production to obtain the desired result.
In digital content creation software, there's often a simple command or option to convert your stepped keys to spline. This action will change the interpolation type, allowing the software to generate intermediate frames.
Animators then play back the animation frequently after making adjustments in iterative steps.
Another key element to take into account between step and split mode is the interpolation curve and algorithm.
4. Interpolation
Interpolation is a mathematical process determining intermediate values between two values depending on an evolution curve. In interpolation mode, the computer generates in-between frames by mathematically calculating the motion along the trajectory established by the keyframes.
Rather than manual drawing or image creation for each frame, interpolation can automate the creation of in-between frames based on an animation sequence's defined start and endpoints.
Different interpolation curves/algorithms bring different results.
Sometimes, you need a linear evolution. The frames change at a constant speed. For example, a car on a highway would have its wheels turn at the same speed.
In other situations, you might want the interpolation to get faster toward the end to make a punch more impactful or the beginning of the movement if you animate a sprinter.
Animators inspect the motion curves in their DCC software's graph editor. This step is critical because, despite the automatic interpolation, you will likely need to refine the curves to reclaim that sense of snappiness that might have been lost going from step to spline mode.
Conclusion
By concentrating on keyframes and leaving in-betweens until later, animators can refine the flow of their animations. This technique forms the groundwork for more intricate details using spline animation, where interpolation creates smooth transitions. As the animation progresses from the structured jumps of stepped mode to the fluidity of spline, the careful balance of timing and motion is preserved.
