Getting the angle of FOV
Author
Hi,
I want to implement the zoom function of a camera so I intend to change the parameter of glPerspective(). Before calling this function, how can I get the current angle of FOV of OpenGL setting?? Thx!
William
Well, let me see... You get the projection matrix (glGet) then let''s say the fifth value (Or [1][1] if you get it as a 2D array) is Val:
Tell me if that works, it''s late so I could make mistakes
.
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We know that (from the MesaGL source code, I downloaded it long ago, lots of good stuff in there):Val = cot(FOV)So, therefore:Val = 1/tan(FOV)1/Val = tan(FOV)atan(1/Val) = FOVTell me if that works, it''s late so I could make mistakes
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Author
thx for your help
It works after I used the sixth element to calculate and I also found that the equal should be:
FOV = atan(1/Val) * 2
It works after I used the sixth element to calculate and I also found that the equal should be:
FOV = atan(1/Val) * 2
Yeah, you''re right 
. When I said fifth I was thinking in a zero-index frame of mind.
[Resist Windows XP''s Invasive Production Activation Technology!]
. When I said fifth I was thinking in a zero-index frame of mind. [Resist Windows XP''s Invasive Production Activation Technology!]
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