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Controller Design: Analog Stick pt.2

After the advent of 3D graphics technology the industry as a whole began to transition into games with 3D environments. I've talked about 2D/3D game design before on this blog in a series called 2D + 2D  = 3D. It t urns out that 3D graphics are not that complicated. It's when 3D graphics and interactivity are combined that things become very complicated. Like never before, 3D games offered another whole dimension to explore. With the world open before us, we first sought a way to move through the 3D worlds intuitively. The 8-way control of the D-pad wasn't good enough. Thus analog control stick technology was embraced.
Sticking Around

We have to be clear about what we mean by "analog." Some stick to the true definition meaning a continuous range of values like the rainbow colors on a light spectrum. A more commonly accepted meaning is simply a wide range of values. How few values a device can have and still be considered analog is generally handled on a case by case basis.

Take the Nintendo 64's controller for example. This device was the forerunner that popularize analog stick controls for video game consoles. With the analog stick and the flagship title Super Mario 64, players coudl stand, craw, tip-toe, walk, and run in seemingly any 2D direction (360 degrees) simply by moving the stick in different ways. Technically the N64 control stick is a clever construction of digital buttons like the D-pad. However, because it offers enough levels of sensitivity it functions as an analog stick for all practical purposes.
While the D-pad has 8 different directional possibilities total, an analog stick has thousands. And while buttons are one dimensional (either off or on),  analog sticks are 2D. To qualify as an analog stick or analog pad there needs to be a springy recentering of the device, a high degree of variables, and two axes of movement. The following are a few unique examples:
  • The N64, GameCube, Nunchuck, and Classic Controller analog sticks all feature an octagonal 8-way rim (see image right). Before reaching the outer limit of the control stick's physical range, players can move the stick smoothly in circles. Press all the way to the outer edge and the stick will be guided into one of 8 directions. With this design you can distinctly feel the cardinal and intercardinal directions much like you would a D-pad. 
  • The 3DS, Wii U, and PSP controllers feature an analog sliding device. These pads have all of the basic functionality of an analog stick but feel different because they lie flat. Instead of pushing around a stick pivoting in a sphere like motion, players slide the pad around along a flat plane. 
  • Pointing sticks (found on laptops). Don't worry. I didn't know the name for these little green or red nubs either. Though they respond to varying degrees of pressure to control the mouse position, these nubs are technically not analog sticks. They don't move enough from their center position and therefore they do not snap back either. 
The pros of analog stick/pad controls are allowing highly variable, intuitive 2D movement. In the same way that controlling 3D actions in more intuitive with a 3D controller, controlling 2D actions is more intuitive with a 2D analog stick. Unfortunately, because the analog stick is a more complex mechanical device more complex drawbacks emerge. While buttons are hard to break due to their small size, short movement range, and rubbery spring back mechanisms, analog sticks are somewhat fragile. The outcome we fear most when we accidentally sit on our game controllers is that we'll break the sticks. In addition to forcing the sticks out of wack, general wear and tear has a noticeable effect on analog sticks. Over time many sticks become much looser. I can't be the only gamer with a controller with drifting sticks. 
When designing mechanics to use analog sticks, most developers know to factor in a dead zone. Because the analog stick is so sensitive, the slightest touch can send a signal to the system. But the slightest touch is too slight. To eliminate false positives from natural stick looseness or slight motions from the player, mechanics are designed not to activate until after the player pushes the stick outside of the dead zone. Another issue that's related to how the dead zone design is when the analog stick sends an unintended signal to the system from the snap back motion the stick makes when recentering. It can be confusing to get a reaction from the game when one lets go of the control stick in the same way that a negative edge button action can be confusing (explained in part 1).
Aside from the loosening of the stick and the erosion of the thumb grips, analog stick controls are very reliable input devices. To highlight its versatility here are a few examples of games that use the stick very well.

Super Monkey Ball 1 & 2. The core gameplay of Monkey Ball consists entirely of guiding a ball through a 3D obstacle course with only the analog stick. The first two games in the console series present challenges that require an extremely high level of sensitivity from the stick and control from the player (see dexterity skills). Additionally, the party games are designed to stress analog stick dexterity over many other facets of skill.

Super Smash Brothers Series. Unlike nearly every other fighting game, Smash Bros is a 2D fighter designed around analog movement. Instead of having to double tap to dash, in Smash players can simply smash (press quickly) on the stick. In addition to dashing players can crawl, tip-toe, walk, and run. In the air players can also control their horizontal movement to a fine degree even while attacking. This allows for highly variable spacing (aiming) which is the most evident in Brawl with its increase focus on aerial battles.  

Geometry Wars Series. Some games are designed with mechanics that ignore parts of the analog stick's 2D range. In Geometry Wars (360/Wii Classic Controller), the right analog stick shoots based on the angle or direction you press. It doesn't matter how far you press in that direction, it only matters what direction. It's also important not to forget how the physicality of input devices shapes our expectations and therefore what feels right. In his article Prototyping Game Feel v.2, Steve Swink talks about the turn radius in Geometry Wars and how it was designed to match the radius and rotation speed of the Xbox 360 analog stick.

Everyday Shooter is an interesting case. I believe this shmup was originally designed for the PC using WASD controls to move around and the arrow keys to shoot. After Sony picked up the game for release on the Playstation Network, the controls were adapted to the PS3 controller. Though you can choose to use any combination of the D-pad or left stick to move and the right stick or the buttons to shoot, the mechanics remain the same. Essentially, the right stick is just a D-pad with 8 possible directions. Even if you try to aim to a finer degree, the ship will adjust the aim to fire in one of the 8 directions. 
Skate. Though most designers use analog sticks for movement, aiming, or camera control, the developers of Skate decided to replace the more traditional button based actions of a skating game entirely with the right analog stick. The video below explains it well. Using the 2D range of the stick, command motions could be designed in ways that reflect the motions of actual skating. I wrote about this inward innovation and others here.

Gamers intuitively make connections and expectations between how we manipulate the controller and the gameplay mechanics (player actions) that follow. The more the input method matches the the virtual actions the more direct the particular mechanic. In other words, we get a sense that what we do to the controller directly affects what happens in the game. Mario's JUMP is designed with much directness. Tap the button and you get a small JUMP. Tap and hold and Mario JUMPs higher. I've known gamers who thought that the NES controller could actually sense how much harder the buttons are pressed to make Mario JUMP higher. We know now that the NES buttons are digital. With only an on and off state the system cannot tell how hard you press. Still, Mario's JUMP is expertly designed so that players make that intuitive connection anyway.

Expectations are similar for the analog stick. The harder you press in a direction the more effort you exert. So if you're exerting more effort the game actions should as well. This kind of thinking works great when designing movement mechanics for characters that can tip-toe, walk, and run based on the analog stick position. However, the design of FPS aiming is much trickier. 

The bottom line is thumb based analog stick control doesn't allow the finest degree of control. Just try writing your name in cursive using a machine gun against a wall in your favorite console FPS to see what I mean. To help, most console FPSs are designed with some kind of sticky aim. Basically, the system knows, or assumes, what you're aiming at and adjusts the aim movement speeds to help you stay on target. When done well, most players don't even notice there's aim assist.
Super Mario Galaxy. The analog stick is a relative control device. Depending on the game state or how the character is oriented, pressing up on the stick may result in proceeding in any one of 360 directions. Designing good relativistic controls requires understanding how quality, feedback design and the other facets of mechanics design come together. Take the Mario Galaxy series. Never before has a game let players explore such a unique and 3D space that is frequently redefined by the gravitation pull of nearby objects. Even still, in space one's sense of direction is even more relative than ever. Running down the side of a planetoid is the same as running up it depending on how you look at it. A key point I must make here is "how you look at it" is largely the result of how the camera is designed. Galaxy's movement controls are built in with a wider turn radius than in Super Mario 64 and with a bit of smart-aim-assist like functionality. As long as you don't let go of the stick and let it recenter, you can push the system far enough that holding down makes Mario move up. As backward as it sounds, it feels completely natural.
To close, analog sticks work best for controlling 2D continuous actions like moving. This is why few gamers spam motions into the control stick. Unlike buttons which tend to activate non continuous, primary mechanics, spamming the stick will most likely make the on screen character shiver shake in place. So if you want to reduce spammy tendencies, go with sticks. In part 3 we'll look at touch screens and triggers.
« Controller Design: Touch Screen pt.3 | Main | Controller Design: Buttons pt.1 »

Reader Comments (2)

Since no one else has commented, I'll chime in with some additional details:

An oft-overlooked aspect of analog sticks is that they're highly dependent on the way a given game is programmed to handle their input. If you compare the aiming control in an early console shooter like Goldeneye or Red Faction to more recent games like Unreal Tournament 3 or Borderlands 2, the difference is night and day. Sure, N64 and PS2 sticks were not built as well as PS3 and 360 sticks, but the bigger difference is in the way the games handle input.

A blogger named Josh Sutphin on Gamasutra wrote a great article called "Doing Thumbstick Dead Zones Right" which shows how different styles of deadzone programming can dramatically affect the way a game controls on the same stick:

Most early console shooters employed a wide, hard radial deadzone which caused very jerky aiming with very little ability for fine adjustments against small/distant targets.

Rotation speed was often scaled on too shallow a curve, resulting in very little difference between a light and hard push on the stick. When you turned sensitivity settings higher, you always lost too much precision, and when you turned sensitivity settings lower, you always lost too much max speed, because there wasn't enough of a curve in rotation rate as you moved from gentle pressure to heavy pressure.

As software implementation of deadzones, pressure curves, and other settings have improved, in-game precision has skyrocketed. In many games, you can shut off auto-aim completely and still do fine against the hardest scenarios the game has to offer. With practice, I have managed to beat bots in ultra high-speed, high-precision PC shooters like Quake 3 and Unreal Tournament 3 on analog sticks, at the the same maxed-out difficulty levels I normally play on a mouse.

A continuing problem is the fact that most games still don't allow users to configure their own deadzone. Instead, they typically possess a hardcoded deadzone designed for the lowest common denominator. So even if you buy a $100 "pro" gamepad with sticks able to register the finest possible adjustments without errors, the game will still ignore fine inputs on the off chance that you're using a beat up $15 offbrand controller you found in a dumpster. Some PC games have ini files that you can hack to get around this, but otherwise, you're stuck.

The other persistent issue is the way analog sticks wear and tear as you use them, resulting is gradually less accuracy and a larger required deadzone to prevent false inputs.

A really good experiment to witness this first hand is to plug a 360 or PS3 controller into your PC and use the freeware, Xpadder, to see how small you can set the deadzone before the controller starts causing your mouse cursor to drift across the screen on its own. If you have a fresh controller just out of the box, you might manage a really tiny deadzone of only 6-7% with no drift, while controllers a few years old need deadzones of 12-24% to keep from running your cursor clear across the screen. Even with a brand new controller, you can often notice the difference with each month of heavy use - it'll need a few more percents of deadzone to stay useable.

The L3 and R3 buttons, while seemingly an efficient use of space, cause a major increase in wear, so I advise control schemes which allow you to avoid touching them as much as possible. It's sad, because changing L3 and R3 to be additional bumpers, shoulder buttons, or middle finger buttons accessible on the back grip, would be an easy design solution to this problem. Some 3rd party pads have adopted solutions like these, but MS and Sony are content to just re-release the same old flawed designs to their next-gen consoles.

The best-kept secret of the analog stick subject is that the entire issue of wear and tear could be avoided by adopting Hall Effect sticks instead of conventional mechanical ones. This type of stick is used in industrial equipment like cranes and forklifts, as well as controls for military drone crafts, and employs a magnetic field rather than mechanical pressure to sense movement, so there is no friction on the parts, and thus FAR less wear and tear from daily use.

Hall Effect was introduced to consoles with Sega's Nights into Dreams analog pad on the Saturn, just 2 months after the N64 launch which put analog sticks on the map. The same hall effect design was used again on the Dreamcast pad. Since hall effect sticks are cheaper to produce than mechanical alternatives, the only reason anyone can guess for Nintendo's, Sony's, and MS's continual use of mechanical sticks is planned obsolescence; they want our controllers to keep wearing out so we keep buying new ones.

Analog controllers have come a long way since 1996, but they still have a long way to go before they're as good as they could be, and comprise truly elegant, flawless product designs.

November 21, 2013 | Unregistered CommenterGnalvl

I forgot one final point:

Compared to a good d-pad, like the Saturn's, which will basically work equally well for anyone regardless of their hand or finger size, analog sticks work much better when the length of the stick is matched to the player's hands.

This is because with analog input, a larger range of motion leads to better mastery of the device's sensitivity. Think about trying to use a mouse when clutter on your desk has only left you a coffee-cup sized area in which to move your hand. If you leave the mouse sensitivity down, it won't get across the screen fast enough within the room available. If you turn the sensitivity up, it'll be so fast that even slight movements may easily miss small icons and text you need to click on.

The same is true of analog sticks. The smaller your stick, the harder it is to hit specific levels of pressure which generate specific rotation speeds when aiming a camera, because the slightest movement makes a big difference. With a longer stick, it's much easier to make fine adjustments because the range of motion at the tip where your thumb grips is much larger. Even if you have a higher sensitivity which allows you to turn quickly to face unexpected events, a longer stick allows you to more readily ride the area just outside the deadzone more easily, maximizing your ability to make very fine adjustments to aim at small/distant targets.

The sticks on most controllers are designed to accomodate the largest audience possible - even small children with small fingers who would have trouble wrapping their thumbs around a large stick. As a result, anyone with bigger hands is not really getting as accurate an analog stick as they could have. There is a simple solution to this - allowing users to adjust the length of their stick as needed.

A few manufacturers have done just this - FPSFreek provides stick extentions which snap on to standard 360 analog sticks. Horri also has an FPS-geared pad with sticks of multiple sizes which screw off and on. I have small hands for a male adult, and even I have found a significant benefit from switching to a longer stick.

If this concept were more well known, and 1st party controllers came with adjustment options for their sticks, the overall level of analog control on consoles would be much more precise. This is another point that shows that controller technology with analog sticks is still at a relatively naive level with room for improvement.

November 22, 2013 | Unregistered CommenterGnalvl

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