#eye trace

[holguindev]

Following The Eye

Eye-Trace For Games

When the camera in a game is done well everything feels just right, everything just flows. It's the reason why Journey, why Inside, why Mario Kart 8, and just about every Nintendo game feels just as if anyone could play them.

Knowing how to deal with the eye not only helps you make your game more accessible but it also makes it easier to follow in the most hectic of moments.

From: PlayDead’s INSIDE

My goal: Is to explain how to design the game around the eye’s limitations and create experiences that are more comfortable for our users. I will start with the simple yet effective concept of Eye-Tracing.

An example:

From: Mad Max Fury Road

Follow the red circle: We can immediately read where the motorcycle is between shots and we see the barrel on the shotgun, each shot takes less than a second, yet we read every beat, and that’s because the eye is directed so well here.

Eye tracing is an editing technique used to direct where the eyes of a viewer will be across several shots, in other words it's strategically moving the eyes of your player to a specific point in the screen and using it in different fun ways.

Create an environment in which you know which part of the frame your player is most likely to be looking at, this can be performed a number of ways but I wont get in the details of composition, color theory, photography or animation. I will only talk about the eyes.

Now, how does something from cinema world, a world where everything is scripted, and there’s a cut every 5 seconds or so apply to an interactive medium? Well the answer is simple it does so in a completely different way.

I will jump back and forth between games and movies but this is a game focused article.

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Do Your Eyes Follow?

What does the player see? What do you as a creator want them to see?

Do those 2 align? Can they?

Eyes have a 5 degree central vision, this is where we read books, if our target moves outside of the near-peripheral section of our eyesight the eyes will have to change positions.

TVs tend to hang in the mid peripheral, it feels as if it covers the whole vision but it really doesn’t. Close one eye and make a frame with your hands observe how much your monitor or your TV takes of your vision space.

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My rules are: 

Screen Is A Plane Not A Window.

Eyes Are Slow.

Eyes Need A Home.

Up And Down Before Left And Right.

One Thing At A Time.

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The Screen Is A Plane Not A Window

The screen is a flat surface, not a window to another world.

The key word here is Planar space! This is the basis of eye tracing, and designing moving media in a way that is easy to read for people. Even 3D movies need to compose in planar space.

Maintaining the focus in a slowly moving point in planar space makes it easier on the eyes because your eyes have to move way less.

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Eyes need a home

Even when there’s nothing to be seen, the eyes should be directed to a point on the screen.

From:Mario Kart 8

In hectic game-play, having one direct point to return to is imperative as it gives the eyes a simple point to return to as they jump from object to object during the action.

In games like Mario Kart the player doesn’t have to worry where the character is, but where the obstacles are.

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Eyes Are Slow

Eyes are freaking slow, if you bring motion to a target and this target moves too fast the eye will unhook from it, this occurs because of something called Saccadic Masking a mechanism in our brain that removes all the blur we should have in our eyesight and replaces it with point 2 in an image.

This means things on the screen need to move at a slow pace but not in any space but in planar space, remember the first rule The Screen Is A Plane Not A Window, as long as the characters move slowly through planar space the characters will be easy to follow, we are aiding the player to follow the character by moving it as little as possible.

If something moves slowly across the screen the eye has an easier time reading it.

if you move something too quickly the eye gets lost.

For example this is easy to follow by the eye.

This isn’t.

From: Playstation All-Stars

Now on this.

From: Super Smash Brother’s Ultimate

Unlike PlayStation All-Stars, Super Smash Brother’s camera is designed around the philosophy of making the action as easy to follow as possible.

Game camera attempts to make the characters move smoothly through planar space, it will even sometimes hook characters if they don’t move for a bit.

This philosophy means everything, this philosophy created this marvel of technical prowess. Regardless of how it was engineered the camera in Smash Brother’s is superbly created.

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Up And Down Before Left And Right

It’s easier for the eyes to follow vertical motion than horizontal motion.

This is why magazines design text in small columns, and entire languages are designed to be read vertically. Eyes find moving up and down more comfortable.

(Read on a large screen)

Up and down.

Left and right.

This also helped Journey’s devs to create a smoother camera that otherwise would have wobbled inelegantly.

Vertical motion will still cause Saccadic masking if motion is too fast, vertical motion just happens to be slightly more comfortable to follow than horizontal motion.

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One Thing At A Time

One thing at a time, and only one thing at a time.

I’m not going against the laws of composition nor framing, you can do amazing things with multiple characters, and crowds. This rule here talks about how even in highly composed shots we still only see one face at a time, one item at a time, or one enemy at a time.

Eyes can only see one thing at a time. Crazy huh? You have to literally stop looking at one thing to look at another. Hell it’s even scientifically proven we can’t multitask. So don’t force people in your supposed-to-be-entertainment product to attempt things that we aren’t biologically designed to do (unless it’s multiplayer, or if you figure it out, who am I to stop you).

From: Super Mario Odyssey

Make sure that if something is happening on the screen that only one thing is happening that requires the player’s full attention, now this may go against the idea of action game-play for a lot of people, specially in games with a lot of AI going at you, this is easily remedied by having only one AI attack at once, think, and ask yourself the question, What is the main focus at this very moment? and make it immediately readable. Yes, even if it’s outside the screen.

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Solutions

I will give some solutions to improve your game on the engineering side.

1) Create the camera system backwards.

Engineer the camera system to respect the points in planar space first and then calculate to it.

2) If you know where the eye is, use it.

Dynamically determine where the eye is right before the next shot, or right before elements are to be displayed.

We can create things that only games can do, we can dynamically adjust the camera, the next shot, or item position for our users.

3) Guide the eye.

It’s your job to guide the eye, and figure out ways in which you can do it the most effectively.

Things like the opening in Journey are just brilliant. The eye follows the character to the top of a hill just to bring an even bigger hill from the horizon.

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The Future

I hope this gives people a better understanding on how the eye works in games and helps us understand the one issue that I think plagues entertainment software the most, we think of the camera as a dual state thing, it’s either a “Game Camera” or a “Movie Camera”, I think we can embrace something that is neither a Game nor Movie camera.

With a better understanding on how to handle eye-tracing we can do things film can’t even imagine, so I hope this article helps you learn something I noticed. And helps you realize that one thing that only your game can do that will blow us all away.

Cheers,

-Fern.H.W.

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