On 6/23/2019 6:03 PM, Mike Horvath wrote:
> Starting with location, look_at, angle and sky, I perform the following 
> operations:
> 
> //--- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- ---
> 
> #declare Camera_Location = <25.000000,15.000000,-33.000000>;
> #declare Camera_Look_At = <2.000000,2.000000,0.000000>;
> #declare Camera_Angle = 70.000000;
> // should be able to set this to false as well
> #declare Camera_Orthographic = true;
> 
> #local CamL = Camera_Location;
> #local CamD = vnormalize(Camera_Look_At - CamL);
> #local CamR = vnormalize(vcross(Camera_Sky, CamD));
> #local CamU = vnormalize(vcross(CamD, CamR));
> #local CamW = vlength(Camera_Look_At - CamL);
> 
> #if (Camera_Orthographic = true)
>      #local CamR = CamR * CamW;
>      #local CamU = CamU * CamW;
> #end
> 
> #declare Camera_Zoom        = 1/2/tand(Camera_Angle/2) * 
> Camera_Aspect_Ratio;
> #declare Camera_Direction    = CamD * Camera_Zoom;
> #declare Camera_Right        = CamR * Camera_Aspect_Ratio;
> #declare Camera_Up            = CamU;
> 
> //--- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- ---
> 
> The code calculates the values of the camera's direction, right and up.
> 
> My question is, how do I do the inverse? I.e. starting with location, 
> direction, right and up, how do I calculate look_at, angle and sky? It 
> seems like pretty simple algebra but I have been hitting my head against 
> the wall trying to figure it out.
> 
> Thanks.
> 
> 
> Michael


Disregard. I got it working.

Michael

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