One of the most important concepts in Interaction Design is affordances. An affordance is about knowing how we can use objects. If a door has a handle, we know we can pull that handle to open it. An affordance is the relationship between the properties of an object, the handle, and our ability to act on it, pulling with our hand. There are lots of affordances all around us in the real world. A panhandle affords picking up, the flat surface of a table affords putting things on it, and the hole of a cup affords filling with water. Affordances aren't necessarily something that are designed into objects. If you're anything like me, the end of a pen affords chewing, and the flat tip of a screwdriver affords opening tins of paint. In Interaction Design, we think of the affordances of user interface elements. In a web page, underlined text affords clicking because it normally means a link. There are many aspects to the designs of buttons that signal the affordance of clicking. Go and look at a load of web pages or user interfaces, and see which parts you instinctively know that you can click on, then look carefully at the visual design and try to figure out what aspects of that design made you want to click. In VR, as usual, the affordances are much closer to the real world than to an interface. Particularly, if you have a six-degree-of-freedom controller, you want to pull door handles, pick up tennis rackets by their handle, and flick switches. Once you've looked at the affordances of buttons on a web page, go back to the real world and look at the web around you. Find as many things that you can use as you can, think about what you use them for, and then think about what features their shape or appearance affords that activity. Particularly look for anything that you use for reasons other than their intended purpose, and see what feature makes them suit that unofficial use. Affordances depend not only on the properties of an object, but also your own ability to act. Recently, after an injury, I was briefly a wheelchair user. Using a wheelchair instead of walking deeply changes the way you see the world. Small steps or potholes that easily afford stepping over, and you don't even notice if you're walking, suddenly become obstacles when you're on wheels. In VR, this relationship between your capabilities and the properties of an object become very important because there are different types of controller. The affordances that you see and you can act on when you only have gaze-based interaction are very different from when you have a six-degree-of-freedom controller. Affordances are properties of what you can actually do with an object. But there are also visual signs that can signal the presence of an affordance. On a door, the handle is the sign that signals pulling, and a flat plate is a sign that signals pushing. But when the signs don't correspond to the true affordance, things can get confusing. Have you ever tried to pull a door handle and the door doesn't open? Only then do you notice a little written sign saying push on top of the handle. The real sign is the handle. That signals pull much more strongly than any writing, and the sign is signaling the wrong thing. This kind of thing happens all the time. It's just a sign of bad design. In VR it happens as well. The designers of Valve's Lab demo pointed this out when they talked about a part of the demo that included a cabinet with lots of drawers, some of which you could open and some of which you couldn't. The ones you could open had green lights, and the ones you couldn't had red lights, but they all had big pull handles on them, and this affordance signals much more strongly that you could open any drawer, and so players spent a lot of time trying to open drawers that they couldn't open. It was a false affordance. One of my favorite examples of false affordances in VR involve tables or desks. A lot of VR experiences involve tables or similar surfaces. In the real world, they afford putting objects on, and often they do in the virtual world. When we finish in VR, we naturally want to put our controllers down on the nearest surface, which might be the table just in front of you. Actually, the table only exists in the virtual world and the controller is a real object. I've dropped controllers on the floor a few times because of that false affordance, and I've seen several other people do it as well. I suspect it's one of the main causes of broken controllers. The message in VR is that you should make sure that the visual design of your objects signal the actual affordances that are possible with that object. In virtual worlds, you often have lots of objects that are just for decoration and can't be interacted with. If you put handles, switches, or similar elements on them, they will seem to afford actions and players will have a frustrating time trying to use them. In fact, you can use the design of objects to signal subtly what you can and can't interact with. Good signaling of affordances can overcome a lot of the difficulties and frustrations of VR.
