Hand tracking and virtual reality are both emerging technologies, and combining the two into a fluid and seamless experience can be a real challenge. This month, we’re exploring the bleeding edge of VR design with a closer look at our VR Best Practices Guidelines.

As an optical motion tracking platform, the Leap Motion Controller is fundamentally different from handheld controllers in many ways. Here are 4 tips to designing for the controller’s unique strengths, while avoiding common pitfalls.

1. The Midas Touch

The mythological King Midas loved being able to transform things into gold – until he realized he couldn’t stop. Your VR demo needs to include safe poses and zones to allow users to comfortably move their hands around without interacting.

Gesture-based interactions should be initiated with specific gestures that are rarely a part of casual movement. (For example, grabbing is a distinct action that can signal intent.) For UI design, Widgets should be positioned (and spaced apart) to prevent accidental triggering. Dynamic visual feedback is also essential. For more, see Part 2: Interaction Design in the VR Best Practices Guidelines.

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EXAMPLE: The interactions in Planetarium involve either grabbing, or interacting with specific UI Widgets triggered from the Arm HUD. You can wave your hands in the air, and the application won’t care.

2. Hand Poses and Interactions

While our software is constantly getting better at tracking potential hand poses, some will always track better than others. Whenever possible, encourage users to keep their fingers splayed and hands perpendicular to the field of view – like the Hovercast Menu system at the top of this post. This is by far the most reliable VR tracking pose. For similar reasons, be sure to avoid interactions that depend on the position of fingers when they are out of the device’s line of sight. Some other generally solid gestures and poses in VR include

  • index finger pointing (as long as it’s visible to the device)
  • grab gestures (with the palm facing away from the device)
  • the “Superman pose” (palms facing downwards, fingers outstretched)

occlusion

EXAMPLE: (Left) What exactly are the fingers on my left hand doing? You don’t know, and neither does the Leap Motion Controller. (Right) In this picture, though, you can see each of my fingers very easily. Between these two extremes, there are an almost infinite variety of possible hand poses. Your design should encourage the latter.

3. Interaction Height

When placing interactive elements like our UI Widgets within your gameworld, try to keep them in the “Goldilocks zone” between desk height and eye level. Below the Goldilocks zone, background interference from glossy tabletops, coffee mugs, and other objects becomes more likely. At the upper range, users might experience neck strain and arm fatigue from reaching up repeatedly.

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EXAMPLE: Soundscape VR features a bank of buttons that are placed at a comfortable level and range.

4. Range and Field of View

If the user can’t see their hand, they can’t use it. While this might seem obvious to developers, it isn’t always to users – especially when focused on the object they’re trying to manipulate, rather than looking at their hand.

Avoid interactions that require a hand to be at rest when near the edge of the field of view, or when horizontal. You can also use disappearing skins that fade out as confidence values drop, color cues to reinforce distance boundaries, and object interactions that persist even if the hand disappears momentarily. (For instance, the star grab in Planetarium will stay in place for a moment if the hand disappears from tracking. If the hand reappears, the stars remain grabbed.)

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EXAMPLE: Whether they’re near my messy desk or a light-blue wall, my hands might not track as well as they should. The Confidence API can tell your application when this might be happening. Check out a live demo of the Confidence API in action on our Examples Gallery.

Our team is constantly working on tracking improvements and new developer resources to address these common challenges, so stay tuned. For more VR design techniques, be sure to read the first three parts of VR Best Practices Guidelines.

Alex is the head writer and blog editor at Leap Motion, where he stands as the final bulwark against bad grammar. Want to share your Leap Motion project? Email acolgan@leapmotion.com or PM leapmotion_alex on Reddit.

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