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Unity custom camera view matrix in shader?

Discussion in 'Editor & General Support' started by valleeey, Apr 3, 2014.

  1. valleeey

    valleeey

    Joined:
    Oct 11, 2013
    Posts:
    27
    Hello community,

    I want to create a custom view matrix so that I can use it in my shader. My question is: how does unity set up the matrix?

    Playing around with Camera.worldToCameraMatrix makes me think that the matrix is set up like this:

    Code (csharp):
    1.  
    2.  
    3. float4x4 customViewMatrix2 ={   right.x,        right.y,        right.z,        -CamPos.x,
    4.                                 up.x,           up.y,           up.z,           -CamPos.y,
    5.                                 -forward.x,     -forward.y,     -forward.z,     CamPos.z,
    6.                                 0,              0,              0,              1};
    7.  
    8.  
    But the right column (CamPos) seems to be not completely right when you add orientation to the camera!

    Looking forward for help!! :D

    Thanks!
     
    Last edited: Apr 3, 2014
    valleeey, Apr 3, 2014
    #1

  2. Graham-Dunnett

    Graham-Dunnett

    Unity Technologies

    Joined:
    Jun 2, 2009
    Posts:
    4,287
    Graham-Dunnett, Apr 3, 2014
    #2

  3. valleeey

    valleeey

    Joined:
    Oct 11, 2013
    Posts:
    27
    Hey Graham,

    thanks for your quick response.

    Sorry, I did'nt make it clear - I definitely need to create a custom view matrix.

    I need to render from different positions in one shader pass and I just have the camera positions stored in GPU memory. So that's the only (fast) solution, I guess.

    So please, when somebody knows how especially the last column of the matrix gets calculated, please tell me! :)
     
    valleeey, Apr 3, 2014
    #3

  4. valleeey

    valleeey

    Joined:
    Oct 11, 2013
    Posts:
    27
    noone? please, I need this for my bachelor thesis and can't figure it out myself! :/

    I need the last column of the matrix. When you have no rotation, the [-camPos.x,-camPos.y,camPos.z] is correct, but with rotation the values are changing.
     
    valleeey, Apr 4, 2014
    #4

  5. valleeey

    valleeey

    Joined:
    Oct 11, 2013
    Posts:
    27
    Finally I could figure it out myself.

    The Unity camera view matrix gets computed like this:

    Code (csharp):
    1.  
    2.  
    3. float4x4 customViewMatrix = {   right.x,        right.y,        right.z,        -CamPos.x*right.x - CamPos.y*right.y - CamPos.z*right.z,
    4.                                 up.x,           up.y,           up.z,           -CamPos.x*up.x - CamPos.y*up.y - CamPos.z*up.z,
    5.                                 -forward.x,     -forward.y,     -forward.z,     -CamPos.x*(-forward.x) - CamPos.y*(-forward.y) - CamPos.z*(-forward.z),
    6.                                 0,              0,              0,              1};
    7.  
    8.  
    The reason for this is surprisingly simple. It's because of the multiplication of two matrices. For more explanation see this link:
    http://schabby.de/view-matrix/

    Hope this'll help someone in the future.
     
    valleeey, Apr 5, 2014
    #5