As a form of animation performance, the law of animation motion, in which artistic expression and technical operability exist in parallel and are indispensable. It is a law which brings together science, artistry, and technology, and it exists as a regular summary of animation movement. The 12 principles of animation are the most well-known laws of motion, and the connection between game animation and it is also inseparable. This chapter focuses on the specific embodiment of 3d game animation under the 12 principles of animation.
1. Squeeze and stretch
Unlike traditional film and television animation, many video game engines do not support scaling of bones due to random-access memory limitations. However, even if the model is not deformable, this principle is still important. Under the premise that the model cannot be squeezed and stretched, most of the characters in realistic games emphasize the stretched posture by stretching their limbs during fast movements, such as jumping, taking off and landing. In cartoony games such as Overwatch and League of Legends, animators still frequently use this principle to achieve the character’s rapid actions, such as drawing a gun.
（Figure 5 Overwatch character McCray’s gun-drawing action）
2. staging
This principle does not directly apply to gameplay animation. Only appear in linear portions of games such as cinematics, where the camera and/or characters are authored by the animator.
3. anticipation
The anticipation is the prelude of the main body’s action, which indicates the direction, strength, size and speed of the main body’s movement. The animator needs as many movements as possible to support the rationality of the character’s actions. If there are too few actions, then the desired action, such as a sprint or a sword swing, will lose weight, but if the time is too long, the player will feel unresponsive. This is not only an aesthetic part, but also an important part of player’s feedback.
4. Straight Ahead and Pose to Pose
In cinematic animation, there is no need to work in the “straight ahead”, and the production is more refined. So pose to pose is the preferred method for most game animations. This is mainly because as the game design progresses, the animation is likely to be changed or even deleted. Keyframe game animations will continue to require iteration, and it is much easier to use rough key pose animations than fully completed animations. Therefore, it is important for game animators not to feel precious to their work. Keeping something in a pose to pose or unfinished state for as long as possible can not only reduce waste, but also allow animators to create more rough versions of animations so that they can eventually mix many animations together to create better and smoother game characters than a single exquisite animation. However, when using motion capture, all of this disappears, and animator basically uses the middle motion as a starting point, then adds key poses and retimes the timing from there.
5. Follow-Through and Overlapping Action
When an object moves, all parts of the object follow the motion at the same time. The movement of the main object will affect the subsidiary objects. Overlapping action cover the concept that different parts of the body will move at different rates. During the boxing process, the head and torso will dominate the movement, with the curved arms dragging back, and the arms bouncing forward before the collision to provide a blow. A common mistake most junior animators make is to have all the elements of a character start or arrive at the same time, which seems unnatural. Although related to expectations, it describes what happens in the action area (contrary to expectations). This includes restoring balance from a jump, or embedding a heavy sword or axe into the ground and being heavily lifted back onto the character’s shoulder. It also includes the movement of secondary items such as cloth and hair in the initial action. Overlapping action is a good way to interpret the weight of an object or character, maintaining a strong pose at this stage will really help the player to read the action better.
6. Slow in and Slow out
This principle describes the visual effects of acceleration and deceleration of movement elements, that is, when the action starts and finishes, due to the weight of the object, the action usually has a slower movement at the beginning and ending. This concept can be easily visualized by moving a sphere in a position. Uniform/straight-line movement will make the sphere move the same distance in each frame, and slow in and slow out will make the position of the sphere gradually approach the starting point and ending point as the sphere’s speed rises and falls.
The important thing is that not everything needs to slow in and slow out. “Therefore, there is once again a conflict between the player’s desire for gameplay to react immediately and the desire for artistry to give the character weight (Jonathan 2019). ” For example, a sword that swings immediately looks very light, so the task of the game animator is to increase the weight at the end of the subsequent game. When the character and the sword return to the idle state, the action can be fast, but it must follow slow in and slow out. Game animators often exaggerate the recoil of a pistol to show its relative power and damage as a weapon in the game, while maintaining the immediate response and feedback of shooting.
7. Arcs
When the elements of the object or character move, most of the action curves naturally present a circular arc, such as the swing of the arms and legs when walking. The part that deviates from the natural curve will be caught by the eye and look unnatural, so the arc is a good way to hone the grace and correctness of the action. Most of the cleanup work to make motion capture work in games is to remove abnormal breaks from the arcs that are naturally generated in human motion, but when repeated in video games, it may seem very obvious and wrong, on the contrary, animating each element of the character so that it follows a clean arc, which can look light or floating when nothing attracts the eye. Just like with overlapping actions, as with most general rules, knowing when to break smoothing will add a higher level of detail to the animation and make it more realistic.
8. Secondary Actions
Secondary actions are used to complement and emphasize the main actions of the character, adding additional details and visual effects to the basic actions. Although it is difficult to include multiple actions in many game animations because they are very concise (secondary action must support and not interfere with the appearance of the primary action), it is these small details that can make a good animation great.
Examples of secondary actions include changes in facial expressions that accompany battle or injury animations, and fatigue reactions that occur when running for a long time. In game animations, additional animations and partial animations are allowed to combine actions on top of basic actions to provide secondary actions that are longer than a individual animation required for player control.
9. Appeal
Every animator should aim for attraction when giving life to a character, but this cannot be expressed in words, so it is difficult to describe. This is the difference between an animated face that can depict real emotions and a face that looks scary. “It is the sum of an animator’s skill in selling the force of a combat action versus a movement that comes across as weak. It is the believability in a character’s performance compared to one that appears robotic and unnatural (Jonathan, 2019). “
Appeal is a magical element that makes players believe that the character they are interacting with, no matter it is in a stylized or a realistic spectrum, and is not to be confused with likeability or attractiveness, because even the player’s enemies must also look aesthetically pleasing and show appeal. This is mainly due to the character design, just like an animator manipulates the character, where the proportion and color division are the first steps in the multi-stage creation process. Through animation and final rendering, the character is as appealing as possible, the simplicity of visual design and the posture of the animation part help to improve the readability of the action, and the clear outline can distinguish different characters.
10. Timing
Timing is the core of the sense of animation, usually used to convey the weight of a character or object. In essence, the timing principle is related to speed, the time required for an object to move or rotate for a distance or angle will make the viewer feel how heavy or powerful the movement is.
This is why every available animation curve editor displays a distance axis and a time axis as the main input for the animator to visualize the speed of the operation they are performing. For example, if animator pose a character with arms outstretched, the impulse in 2 frames is faster than the impulse in 5 or more frames.
With reference to slow in and slow out, proper timing ensures that the character or object obeys the laws of physics. The faster the action, the lighter the weight, and vice versa.
In addition, the timing of the reaction gives the individual time to breathe, such as holding a posture after swinging the sword before the next swing, so that the player can see the working process of the game character.
11. Exaggeration
Real life never seems real enough. If people want to watch the action performed by a real person, such as jumping from a height and landing on the floor, and accurately copy it into animation, the character may look slow and unsightly. Real movements will not follow a perfect arc, nor does it create attractive or powerful silhouettes. In animation, we hope to create hyper-realism and better present the existence in real life. Especially in game animation, we usually have to create actions that look great from all angles, not just from the fixed camera perspective of traditional linear media. That is why one of the best tools in the animator’s Toolkit is to exaggerate what already exists. When referencing the action, the animator must reinterpret the action in a “super-real” way, emphasizing the posture and keeping it longer than in reality.
Care must be taken to ensure the consistency of all exaggeration levels throughout the project, and this is mainly maintained by the animation leader or director, because the exaggeration level is a style choice, and the inconsistency between actions (or between animators) will
stand out and be unattractive when players play the game in the whole game.
12. Solid drawings
Although it may not seem relevant at first glance in the age of 3D animation, it must be remembered that drawing is a basic method of conveying information among team members, and using thumbnails to explain problems or find solutions happens almost every day in the game design team.
All extraordinary animators can easily draw design concepts, and this skill is especially useful in the early stages when designing characters to illustrate the advantages and disadvantages of specific visual elements. Although it is no longer done on the paper, when animating a character in 3D to help pose and understand the limitations and working principles of body mechanics, an understanding of volume and three-dimensionality is still essential for animators.