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Question What is cullingMask ^ 0x8000000 doing for?

Discussion in 'Scripting' started by WayneJP, Sep 30, 2022.

  1. WayneJP

    WayneJP

    Joined:
    Jun 28, 2019
    Posts:
    44
    I saw this two line in a tutorial, but it doesn't explain this.

    Code (CSharp):
    1. camera1.cullingMask = cullingMask ^ 0x8000000;
    2. camera2.cullingMask = cullingMask2 | 0x8000000;
    The binary form of 0x8000000 should be 1000 ...000, right?
    Then why use exclusive OR operator to compute these two bitwise?
     
    WayneJP, Sep 30, 2022
    #1

  2. MelvMay

    MelvMay

    Unity Technologies

    Joined:
    May 24, 2013
    Posts:
    10,512
    One is toggling the bit #27, the other is forcing bit #27 on.

    If they were forcing the bit off, they'd do something like:
    Code (CSharp):
    1. camera1.cullingMask = cullingMask & ~0x8000000;
    I don't like using hex like that, especially if it were a tutorial. I'd much rather express it as:
    Code (CSharp):
    1. camera1.cullingMask = cullingMask ^ (1 << 27);
    2. camera2.cullingMask = cullingMask2 | (1 << 27);
    Personal preference though.

    As to why the XOR, you'd have to go ask whoever wrote the tutorial; code doesn't explain the why.
     
    MelvMay, Sep 30, 2022
    #2
    PraetorBlue, orionsyndrome and Bunny83 like this.

  3. WayneJP

    WayneJP

    Joined:
    Jun 28, 2019
    Posts:
    44
    Thanks! Your code is more readable. I'd like to use yours.
    And, it's "cullingMask2 | (1 << 27);" ,right? not "cullingMask2 | (1 < 27);"
     
    WayneJP, Sep 30, 2022
    #3
    Bunny83 likes this.

  4. MelvMay

    MelvMay

    Unity Technologies

    Joined:
    May 24, 2013
    Posts:
    10,512
    Go ahead but if you're following a tutorial, I'd follow it exactly. Totally up to you.

    Yes, just a typo in the forum.
     
    MelvMay, Sep 30, 2022
    #4
    Bunny83 likes this.