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Question How to get Touch.radiusVariance with new input system?

Discussion in 'Input System' started by lthaca, May 10, 2024.

  1. lthaca

    lthaca

    Joined:
    Feb 23, 2021
    Posts:
    9
    Hi all,

    I've just migrated to Unity's new input system and quickly realized that the new touch system no longer has a property for Touch.radiusVariance. I use this property to normalize input sizes for a range of iOS devices and without it I will be forced to rewrite a perfectly functional input class. It would be much simpler if I could recreate the radiusVariance property that Unity used in their old input system. Does anyone know how Unity calculated radiusVariance in the past?
     
  2. lthaca

    lthaca

    Joined:
    Feb 23, 2021
    Posts:
    9
    After firing up a build that uses the old input system I was able to gather some data points from a few iOS devices:

    iPad
    - DPI: 264
    - Diagonal Pixels: 2560
    - Aspect Ratio: 1.333333
    - Radius Variance: 5.21875

    iPhone 12
    - DPI: 460
    - Diagonal Pixels: 2789
    - Aspect Ratio: 2.164103
    - Radius Variance: 6.065735

    iPhone SE
    - DPI: 326
    - Diagonal Pixels: 1530
    - Aspect Ratio: 1.778667
    - Radius Variance: 6.411896

    After recording a variety of touch inputs, it appears that Touch.radiusVariance = the difference between 2 sequential radii / 2.

    Using the iPhone SE as an example, here are some possible Touch.radius sizes:
    - 12.82
    - 25.65
    - 38.47
    - 51.31
    - 64.13

    The difference between each sequential radius is roughly 12.82, which also happens to be the minimum Touch.radius size for this device. If we take that difference and divide it by 2 we get 6.41, or, if recorded with double precision, 6.411896, which is the radiusVariance for this device.
    i.e., radiusVariance = (38.47 - 25.65) / 2.

    I feel that I am getting closer to a solution but am still unsure of how Unity determines the Touch.radiusVariance as well as the possible Touch.radius sizes for a device. For now, I will be able to set the radiusVariance by referring to a constant variable after verifying the user's device. However, I am a bit uncomfortable with this solution since there might be devices that do not fall into the categories of devices I have recorded. I would much rather be able to dynamically determine the radiusVariance of a device based on the specifications of that device.

    In the meantime, I am currently exploring the radius.sqrMagnitude and radius.normalized of Unity's new input system. There seems to be very little documentation on these properties, but from what I can tell:
    - radius.sqrMagnitude = (radius.x * radius.x) + (radius.y * radius.y)
    - radius.normalized = radius / (√radius.sqrMagnitude)

    If I can use these properties to determine the sequential difference of radii or the minimum Touch.radius then I should be able to gather the Touch.radiusVariance as well.

    I will continue researching and if I come across anything interesting I will be sure to post it here.