挤压和伸展（Squash and Stretch)
Adding Weight to Your Game Design
Weight is a physical and emotional sensation that people feel everyday. And conveying that in a visual way can be incredibly challenging. But it is something animators do all the time, and the principles they use can be applied to game design.
In fact, it needs to be, as many of these principles are sacrificed by the animator for the good of playability. Thankfully, since both animators and designers have to juggle multiple disciplines to bring their creations to life, they speak much of the same language. They just use a slightly different alphabet.
Each part will lay out the 12 principles of animation, and how they are not only used in animation but how they directly relate to game design. Both animators and designers will realize quickly that many of these are unspoken truths, but the benefit comes in knowing that they can now speak to each other on a deeper level. A level that takes animation and design past being purely functional, but now fully functioning towards creating an honest experience.
It is how both can add an extra sense of weight and purpose to the game and the characters within it. Many of these fundamentals are inter-connected, and it is through a combination of all of these working together that you will have characters that move with weight and emote with weight. And that is what will stick with players.
“It is important for the animator to be able to study sensation and to feel the force behind sensation, in order to project that sensation.” – Walt Disney
Squash and Stretch
Applied to Animation
This is the most visible expression of weight and the first thing animators learn and love. The easiest way to show this is with a ball bounce.
Instead of just having a static circle bounce up and down, to show weight it will stretch as it falls, squash when it lands, and then stretch again as it travels back up. That movement of mass throughout the object visually defines how the body handles its weight.
When applying this to a character, think of a jump. Before they can lift off, they must first compress down, to store all that energy like a spring. Then when they take off, they stretch wide, no different than a ball bounce.
But this is also done in facial animation. If you want to make a scream feel powerful, have the face scrunch up, with the characters eyes closed and brows furled. And even for small moments, you want to feel it, even if you don’t see it as much. Because again, this is how people will perceive how the body handles and distributes its mass.
The biggest pitfall of squash and stretch, when used sloppy, is that the object or character will change or lose volume. And that is the most important thing to remember, the overall weight/mass of the object must stay the same when at rest, stretched and squashed. Changing mass means an instant loss in weight.
Applied to Game Design
In game design terms, squash and stretch is essentially contrast. Let the game store up, coil, for what is about to come and after you have done so, let it loose on the player. Make sure when leading in and out of each action, they feel the stretch.
Stretch their abilities, stretch their resources, stretch their economic investment. Then let the impact of the squash take over so the player can see just how much weight and mass they have been carrying around. Because without lows, you can’t have highs. And vice versa. This contrast is the core of what will not only make the player see the weight, but more importantly, FEEL it.
If you can build contrast into every action, no matter how minor, you will be creating a sense of weight in everything the player does. Just remember, that volume can not change. This will give it solidity, no matter how far you push it. This will give whatever you are creating truth.
The easiest place to put this to practice is with guns. If it is a low powered, rapid fire weapon, then the stretch and squash will be minimal. Now think of a gun that allows you to charge the blast. The longer you charge it, the more powerful the blast. You are squashing the power to its limits, so the blast can stretch out into a beautiful ballet of destruction.
In both instances, you will instantly feel how much general squash and stretch is needed. But fine tuning them to feel right, beyond just look right is the key. A common tip animators give is that it is easier and faster to push it too far and pull back, then to not go far enough and keep incrementally pushing it up.
I’m not saying shoot for the furthest star in the sky, and pull back to the star closest to you. Go into it knowing which star cluster is the one that is probably the best fit, and aim for the furthest star in that cluster. Because as time goes on, things naturally tighten up and get pulled back as you polish your creation.
Now with player controlled characters, this principle is something that is quickly sacrificed, as taking the time to squash means taking the control away from the player for a moment, while they are stuck in place, storing the energy that is about to released.
But there is a tactile squash that the player feels when they press the button on their controller or click their mouse. That can be a great step towards making the player feels the squash, even if they can’t see it as much as the animator might like.
Squash and Stretch are the easiest way to quickly add weight to anything you are working on. And because of that, it can also be a favorite trick for people to use and overdo.
But as long as you keep the core of the creation truthful, and care first and foremost about the feel of each over the visual, it will always be a solid method towards conveying weight.
Applied to Animation
In every action, you have anticipation. This may be the most important tool animators have when it comes to storytelling and action. And at its core it is one principle that is most commonly used by game designers. Not only is anticipation in every action we do, and needed to convey a sense of weight, but it is also used to draw the attention of the player before an action happens. For a visual example of anticipation, think of a baseball pitcher. First they will wind up before they even release the ball. Without anticipation, actions become confusing and lose weight without anything to describe HOW they get to where they were going. Anticipation is also the first step in getting the player invested in what is going to happen as they actively engage their mind in the possibilities for what is coming next. And that is an incredibly powerful tool to have when trying to convey a story, movement or emotion with any sense of weight.
Applied to Game Design
In games, anticipation is most visible and commonly used with enemy attacks. To really have a powerful hit or to get the player invested in what is going to happen next, anticipation is employed. The enemy will rear back and give the player a tell, to let them know what is coming. Visually the twist, torque, and shift of their whole body weight makes what is about to happen feel powerful. But it also engages the player to think about when the attack is coming and how best to deal with it. And those moments of drawing conclusions and problem solving is why people play games. Without anticipation, there is no weight to any action that takes place within the digital world or the player’s investment into the world. And the longer you anticipate and build up the action, the more powerful the implied action is expected to be. Likewise, smaller anticipations mean smaller payoffs. You can see how anticipation builds directly from squash and stretch.
Anticipation is also when you can also add a lot of character and personality to the action or mechanic. This is a big reason PunchOut is so successful in not just creating memorable characters, but also great gameplay. The anticipations perfectly match in visual, payoff, gameplay and personality to craft fully fleshed experiences. If a character anticipates, it shows they are thinking about what they will be doing next. If they anticipate in a unique way, it gives some sort of insight towards HOW they think. And giving a thought process to a character is the number one way to make them feel alive and aware of the world.
But beyond just conveying the actions of a character, it is also used to prepare the player for something that is about to happen. Think of the age old tactic where you let the player stock up on health before a big encounter. When you come across a big cache of ammo and health, you anticipate a big battle. And because of it, you better deliver a great battle as a designer, because they are aware of what is coming, and in their mind are already starting to come up with an idea of what it could be. And that is the sweet spot, because you have engaged the player’s mind to start thinking through the rules of the world and piece together a solution to a problem that hasn’t even been posed yet.
And while it can be very satisfying to match or beat those expectations, it isn’t always about delivering on that expectation. You can build something up, but then flip those expectations on their head. And if it is appropriate to the anticipation, it can be even more meaningful. In fact, any successful twist is playing on those pre-conceived assumptions associated with the anticipation. The action can also be smaller than the anticipation, which is a staple of the comedy genre. Take the pitching analogy of before. Think of the Disney animated short where Goofy begins an elaborate wind up, building intense amounts of energy, only to finally pitch the ball by gently flicking it forward. Over the top, and slightly cliché, though still good for a giggle. But, when done subtly, it should be felt by the player, not seen. If it is too much, it will pull the player out of the game, because it will no longer be believable. If you have none, they will be pulled out because it doesn’t feel real or attached to the rest of the experience. But both have to be rewarding to the player and the payoff needs to match the anticipation.
This is one of the most powerful tools in our box, as it is entirely built around involving the player. And because of that, their investment is immediate and our ability to deliver can go beyond just narrative or visual payoffs. Their investment means they can react to the anticipation and either allow it to play out, or change the outcome. And for those changes to have weight, not only do the repercussions need to be meaningful, the anticipation leading up to those player choices is what will make them care about getting the chance to make them in the first place. (Source: Gamasutra)