如上图，这是Richard Williams的《Animator’s Survival Kit》中关于身体运动的弧线描绘。注意身体每个部分的运动变化，特别是臀部。
Adding Weight to Your Game Design Part 7: Arcs
by Michael Jungbluth
Applied to Animation
This is the principle that probably everyone has some knowledge of. One of the quickest ways to rob something of feeling fluid, organic or alive is to move it in a straight line. Sure, straight lines may be the fastest way to get from point A to point B, but they are also the most boring. They are all about the destination, and care nothing for the journey. And that journey is where you find growth and meaning in a character.
In animation, think again of the pendulum. It doesn’t move from apex to apex in a straight linear fashion. It drops in the middle, creating a beautiful arc that gives it weight, and fluid motion. Arcs are what animators love more than just about anything else. It is pure beauty in motion and what makes the movement between key poses fun to watch. The extreme of the arc conveys so much, be it big and grandiose, or small and contained that is impossible not to enjoy the path that gets you there. It shows the personality of the character and leads the eye through a smooth ballet of motion. Likewise, lack of arcs is how you can make something feel cold, weightless and mechanical, which is useful when animating a robot… or Spock.
A page demonstrating arcs during body movement from the Animator’s Survival Kit by Richard Williams. Notice how there are in every part body parts movement, even the hips.
Applied to Game Design
In a narrative sense, this principle is a no brainer. This is the classic narrative arc that everyone learned in grade school. A character or story arc is the fundamental of creating a strong narrative. Every character & story must have progressive challenges that allow them to grow. And as those challenges increase, they reach an eventual climax, which is then resolved.
And in game design, arcs can work much the same way. It means you are starting the player on a journey, or growing a game mechanic organically. As they move forward in the game, it builds, and builds until eventually some sort of resolution is required to make it feel complete. Often times, this means adding more power or functions to the mechanic until it maxes out. But at a certain point, you need to know when to pull back on how much is too much, and allow the player to digest everything you have given. As this mechanics arc is pulling back, the player will feel comfortable, and more than willing and capable of digesting the next mechanic’s arc. Arcs are what link everything together towards a complete and final point, as well as how you create beautiful and flowing overlapping action. But be aware of the staging of your arcs to make sure that the one with the biggest arc is the most important at that moment or to the overall game. Everything else needs to have smaller arcs that will not compete, but flow seamlessly compared to the larger one.
Notice the hierarchy of each arc and how the smaller help to hold up the main story arc.
If every enemy, weapon and level can have an arc, no matter how small, they will feel far more connected to the world they reside in. And it will give each their own history and experience, making each feel like a fully functioning element of the gameplay experience. In most cases, this already happens on a regular basis. When you encounter a new enemy in a game, there is usually a unique intro for them, which is the beginning of the arc. You then fight them, through different attacks and stages, until finally you defeat them, which is the climax. At which point, you want a death or surrender that matches the arc leading up to it. This works exactly the same with puzzles. You establish the layout and tools. You allow the player to face each step of the puzzle, growing the challenge, until they complete it. And just completing a satisfying puzzle is often times the resolution to the arc for the player. If built up properly, and fluidly, then the resolution will resound strongly for the player.
But remember, when leading a player through an objective or level, that the straight path will always feel the most mechanical. Let them feel the organic flow of an arc as they go through a level. Like a roller cost, let the dips take their breath away while the hills make them hold it. But keep the arcs clean and fluid, so that it feels effortless. Because the arcs are where the beauty lies and different points in an arc carry different sensations of weight. The moment you nail the arcs is the moment you can get lost in the motion and just naturally feel it flowing throughout everything you do. And that is the moment that the player and the game become a seamless unit.（source:gamasutra）
Adding Weight to Your Game Design Part 8: Secondary Action
by Michael Jungbluth
Applied to Animation
Secondary action in animation is everything from hair, to capes, to tails, to flags. It is the parts that aren’t necessary to the core action, but add extra visual flare. When you look at a person, the root of the body is the main action, and everything else is secondary. It is ambient, but reliant on whatever it is tethered to. It is the icing. It is also a great way to see where the weight of something has just come from or where it will be going as secondary actions are often very light and almost weightless. In fact, a lot of secondary action is shown by using follow through and overlapping action.
The secondary action of Luxo Jr’s forward motion is the rippling of his power cord which shows clearly where he came from and how he moved.
Where secondary action really becomes powerful is when it comes to acting in your animation. The secondary action is what can be added to help establish and push the personality. So instead of just adding a bounce to the step of a happy person walking, you can also make them whistle. That whistle isn’t necessary for the character to continue walking, but it helps to establish their pleasant mood and makes them feel even more alive.
Applied to Game Design
In games, secondary objectives and powers need to work the same way. They can be their own entity, and they can be beautiful, but they must stay tethered to the main objective and not become so elaborate that they distract from it. They should feel like a natural extension of it, or at least something that is relevant to the main purpose of the game. They should feel like that whistle, adding to the overall mood, atmosphere or purpose, but not necessary for that purpose to go on. In and of itself, it is very light, and almost weightless, like a random swatch of cloth blowing through the air. But, when attached to something more substantial it helps to define the form underneath or trail behind showing off just how much power it is attached to. It is transformed from being just a random piece of cloth floating in the air into a flag, proudly displaying any number of symbolic and meaningful messages.
Think of any secondary mission or quest that quickly grew repetitious. More than likely it had you collecting something you didn’t care about and in all honesty the game world itself didn’t care about it either. That is probably because it didn’t match the main action of the game. Because without that anchor, secondary actrions are lost to the wind, aimlessly floating in an ocean of meaningless grind fests.
It is also important to use secondary action before or after a major action. If you try to use them during a large main action, they can get lost. Take for instance a facial expression. If you have a change of expression, which is signifying a change in thought process, during a fast action, it will be lost in the motion. The change in expression should happen before or after a move. This is just another way to keep it tethered to the important action. If you layer too many secondary objectives during a major, important quest, you will run the risk of overwhelming the player & having them become lost as to what is really important at that moment. Likewise, if you give a power, weapon or mechanic too many secondary functions, or introduce them during intense moments, the player can miss it because they are too focused on what needs to be done immediately.
Imagine each attachment is a bullet point on the back of the box. Sure, the back of the box looks impressive, but when put into effect, this is all secondary without any primary to hold it together.
The secondary action is often what players notice first, and often times is what they are instantly drawn to. Because they are so emotionally and visually loaded, its easy to overdose on them. But they themselves are only a way to help add attention to the weight of the core, and should be only heavy enough to not get lost in the rest of the game. Just remember them as a flag. It says a lot about the people, country, and ideology of where it is located, but without a flagpole to attach it to what is really important, it is just a piece of cloth floating in the breeze.（source:gamasutra）