Week 7, Part 2: 30 March - 6 April [Leap Motion, Prototype]

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Thinking of possible uses of the Leap Motion in the application, I ruled out a pop-up menu as this could only be used to trigger scene changes – not the level of engagement the project requires.
Despite this, I was still able to draw inspiration from the ‘Hover-UI-Kit’ menu I experimented with in the previous blog entry, in Unity. Using a gesture to activate a ‘mode’ then more intuitive movements within the mode for further functionality.

Using the hand to select parts of the airship to then display related information was the idea I decided to develop. This could be done with relative ease through raycasting out from the hand prefab to detect colliders on a ship model.
I used the last bone in the index finger for the origin of the ray, casting the ray forward in the direction of the bones Z-axis. Once this functionality was implemented it needed to be made toggleable, triggered by a user gesture.
Leap Motion provides an example script to detect predefined hand positions. The script works by tracking each digit’s tip, relative to the palm and wrist positions to detect whether fingers are extended. Each fingers position is tracked continuously and its position used to update an enum for each finger (extended, not extended, or either). The fingers’ states are then used to detect gestures. The states enum is set to public, which can then be selected from a drop-down menu in the inspector.
Initially toggled the ray by making a fist, but through testing this was later improved to the point gesture itself (triggers when middle, ring and little finger are not-extended), removing the need for a different toggle gesture.

I began entertaining the possibility of using leap motion when I saw there was no explicit requirement of connection to a computer as I had expected. By using a USB-C/micro USB to female USB adapter, Leap Motion can be connected to the android device itself.
However, after securing the device to my phone in this way, I was forced to reconsider the use of Leap Motion while physically mobile at the exhibition. All other users would also need to secure the device to their phone/phone case with non-reusable adhesive. This isn’t ideal as it may damage their property, will be relatively expensive and not reusable and if not done properly may result in device damage. These factors make the Leap Motion an impractical choice as an application peripheral.

As an alternative to physically moving around the scene, I considered using the hand prefabs position to translate the camera.
Initially, I assumed it would be necessary to get a vector between parallel joints to calculate the rotation, pitch and yaw of the hand prefab.
Luckily, I consulted the Leap Motion documentation before implementing this approach as it showed that the hands rotation and pitch can be accessed from the instance of the hand prefab. It was then a matter of comparing these values to defined thresholds to trigger movement of the camera.

After implementing this, I found the camera would often not respond immediately to input, or move along or rotate about unintended axis. After writing the position values of the hand to the console to locate the issue, I found that even when the user holds their hand as still as possible, erratic value outliers are returned.
I altered the thresholds to increase the size of the deadzone. This separated the range of motions to a suitable degree, preventing hand position from triggering an alternate command.

Using Leap Motion to steer and select
If I were to continue development using the Leap Motion, I could improve the reliability of data given by the Leap Motion by averaging the data to eliminate noise. Averaging the data will add latency, so testing would be needed to balance the results accuracy/latency.
An alternative implementation would be to apply smoothing to the data. Creating a weighted average function, where the further the new data is from the previous value, the less weight it is given.
While Leap Motion proved to be an effective method for obtaining user input, unconsidered issues regarding the practicality of its use will make it incompatible with the project I am building.
Using the device would also restrict the number of potential simultaneous users to the number of Leap Motions brought to the exhibition.

Raycasting out to detect interactable objects was a far better option than the slow transition of steering the ship to trigger UI, and could be made to work with my recent Vuforia build which allows the player to physically move about the scene.
I will attempt to create a similar functionality using Vuforia next week.


References:
https://developer.leapmotion.com/documentation/v2/unity/unity/Unity.HandController.html

https://answers.unity.com/questions/547020/unity-and-leap-motion-help-with-jerkiness-of-input.html







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