A gaze indicator, basically a cursor, provides continuous feedback for the user to understand what the HoloLens understands about their intentions.
Targeting of content is done primarily with the gaze vector (a ray controlled by the position and rotation of the head). This provides a form of direct input for the user that needs little teaching. However, users have difficulty using an unmarked center of gaze for precise targeting. The cursor allows the user to understand their more-precise center of gaze and acts as feedback to indicate what area, hologram, or point will respond to input. It is the digital representation of where the device understands the user's attention to be (though that may not be the same as determining anything about their intentions).
The feedback provided by the gaze indicator offers users the ability to anticipate how the system will respond, use that signal as feedback to better communicate their intention to the device, and ultimately be more confident about their interactions.
In general, the indicator should move in approximately a 1:1 ratio with head movement. There are some cases where gain (augmenting or diminishing movement noticeably) might be used as an intentional mechanic, but it will cause trouble for users if used unexpectedly (note that there is a tiny bit of 'lag' recommended for the cursor to avoid issues with fully display-locked content). Most importantly though, experiences should be "honest" in the representation of cursor position - if smoothing, magnetism, gain, or other effects are included, the system should still show the cursor wherever the system's understanding of position is, with those effects included. The cursor is the system's way of telling the user what they can or can't interact with, not the user's way of telling the system.
The indicator should ideally lock in depth to whatever elements the user can plausibly target. This may mean surface-locking if there is some Spatial Mapping mesh or locking to the depth of any "floating" UI elements, to help the user understand what they can interact with in real-time.
Cursor Design Principles
- We recommend that the cursor is always present.
- If the user can't find the cursor, then they're lost.
- Exceptions to this are instances where having a cursor provides a suboptimal experience for the user. An example is when a user is watching a video. The cursor becomes undesirable at this point as it's in the middle of the video all the time. This is a scenario where you may consider making the cursor only visible when the user has their hand up indicating a desire to take action. Otherwise, it's not visible on the video.
- The cursor should be no larger than the available targets, allowing users to easily interact with and view the content.
- Depending on the experience you create, scaling the cursor as the user looks around is also an important consideration. For example, as the user looks further away in your experience perhaps the cursor should not become too small such that its lost.
- When scaling the cursor, consider applying a soft animation to it as it scales giving it an organic feeling.
- Avoid obstructing content. Holograms are what make the experience memorable and the cursor should not be taking away from them.
- Although there is no one right cursor shape, we recommend that you use a directionless shape like a torus or something else. A cursor that points in some direction (ex: a traditional arrow cursor) might confuse the user to always look that way.
- An exception to this is when using the cursor to communicate interaction instruction to the user. For example, when scaling holograms in the Windows Holographic shell, the cursor temporarily includes arrows that help instruct the user on how to move their hand to scale the hologram.
Look and feel
- A donut or torus shaped cursor works for a lot of applications.
- Pick a color and shape that best represents the experience you are creating.
- Cursors are especially prone to color separation.
- A small cursor with balanced opacity keeps it informative without dominating the visual hierarchy.
- Be cognizant of using shadows or highlights behind your cursor as they might obstruct content and distract from the purpose.
- Cursors should align to and hug the surfaces in your app, this will give the user a feeling that the system can see where they are looking, but also that the system is aware of their surroundings.
- For example, in the Windows Holographic OS, the cursor aligns to the surfaces of the user's world, creating a feeling of awareness of the world even when the user isn't looking directly at a hologram..
- Magnetically locking the cursor to an interactive element when it is within close proximity. This can help improve confidence that user will interact with that element when they perform a selection action.
- There is a lot of information in our world and with holograms we are adding more information. A cursor is a great way of communicating to the user what is important.
- If your experience is focused on a single hologram, then perhaps your cursor aligns and hugs only that hologram and changes shape when you look away from that hologram. This can convey to the user that the hologram is special and they can interact with it.
- If your application uses spatial mapping, then your cursor could align and hug every surface it sees. This gives feedback to the users that HoloLens and your application can see their space.
- These things help reinforce the fact that holograms are real and in our world. They help bridge the gap between real and virtual.
- Have an idea of what the cursor should do when there are no holograms or surfaces in view. Placing it at a predetermined distance in front of the user is one option.
As we mentioned that its good practice to have the cursor always present, you can use the cursor to convey some important bits of information.
- As the user is gazing at a hologram and the cursor is on that hologram, you could use the cursor to convey possible actions on that hologram.
- You could display an icon on the cursor that the user can for example purchase that item or perhaps scale that hologram. Or even something as simple like the hologram can be tapped on.
- Only add extra information on the cursor if it means something to the user. Otherwise, users might either not notice the state changes or get confused by the cursor.
- We could use the cursor to display the user's input state. For example, we could display an icon telling the user if the system sees their hand state. This will tell the user that the application knows the user is ready to take action.
- We could also use the cursor to make the user aware that there is a voice command available. Or perhaps change the color of the cursor momentarily to tell the user that the voice command was heard by the system.
These different cursor states can be implemented in different ways. You might implement these different states by modeling the cursor like a state machine. For example:
- Idle state is where you show the default cursor.
- Ready state is when you have detected the user's hand in the ready position.
- Interaction state is when the user is performing a particular interaction.
- Possible Actions state is when you convey possible actions that can be performed on a hologram.
You could also implement these states in a skin-able manner such that you can display different art assets when different states are detected.
Designing without a cursor is recommended only when the sense of immersion is a key component of an experience, and interactions that involve targeting (through gaze and gesture) do not require great precision. The system must still meet the needs that are normally met by a cursor though - providing users with continuous feedback on the system's understanding of their targeting and helping them to confidently communicate their intentions to the system. This may be achievable through other noticeable state changes.