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This is Twenty Milliseconds, a site documenting what works and what doesn't in virtual reality design.

3D Object Tracking Works

Summary: Tracking opponents in games via a "radar" system has had poor usability in the past. In part, this comes from not turning the radar to match the user's field of view, and in part from representing a 3D area in two dimensions. Headsets make it trivial to solve these problems and increase the usability of radar UI's.

In head-to-head combat games it’s important to be able to find your opponent and ensure that they are not sneaking up from behind you. Traditionally, developers have done this by projecting a 2D map in the corner of the screen, with small icons indicating your position and the position of the other players in the world.

Presenting a 3D radar view in 2D has not worked very well. On a 2D map, you are always missing a dimension that makes it difficult to determine how close or far your enemy actually is.

In Starfox 64, your ship, your teammates’ ships, and the bad guys are represented on a square map, even though your ship can move in three dimensions. It’s also not clear from the HUD which direction your ship is flying, which probably explains why the game designers added extra arrows to guide you to the bad guy.

Starfox HUD Photo credit: Nintendo Life

In Mario Kart 64, the level map is in 3D, and you get an overhead view of the characters positions. This works to an extent. You still have to compute the position of your car relative to the other cars, to determine whether they are left or right of you, if your car is facing any direction but “up”. The design of the level may also have been limited by the constraints of the map.

Mario Kart HUD Photo credit: Giant Bomb

Headsets Allow for 3D Radar Tracking

With a headset you can present different images to the left and right eyes, allowing for actual 3D radar displays to be present. With a 3D radar display, aligned so the far end of the display is always showing the view directly ahead of you, the display maps perfectly to your perception of the world, allowing you to “see” bad guys even when their ships are not visible.

Here’s an example from Elite: Dangerous. Above a circular plate, in the center of the display is your ship; little red dots fly around it to indicate the position of enemy ships.

3D Tracker in
Elite: Dangerous 3D Tracker in Elite: Dangerous (photo from BlendMan).

In this screenshot it looks like vertical lines have been drawn to indicate the enemies’ height and distance from you; in the latest demo I have seen, the lines are gone.

A caveat

3D Radar may work better with a headset, but there might not be as much of a need for it when you can look in all directions. It’s important in games on a monitor or TV where your field of view is constrained by the edges of the screen, and you can’t turn your ship to see all of your enemies. In Elite: Dangerous for example, you can see almost a full hemisphere above and around your ship.

In the future (once I have an Oculus), I’ll hope to test this with users, asking them to turn and locate an enemy, and measure the amount of time it takes them to do so.