View Full Version : how does orthographic camera fov work?

02 February 2009, 06:42 AM
ok i have 1 100mx100m plane centered at the origin. I am trying to setup a orthographic camera from the top view to fit to this box exactly.
my camera is facing down -z how can i calculate what my fov should be?
cam is at 0,0,0 also...

02 February 2009, 06:58 AM
Ortho camera FOVs depend on the target distance. Other than that, it's the usual trigonometry bits.

I.e. if you have a target 100 units away from the camera and you want the camera to cover, horizontally, 100 units as well, then imagine the full horizontal FOV as two right triangles with the target distance as the adjacent length and the desired view in units, divided by two, as the opposite length.

halfHorizontalFOV = atan(opposite/adjacent) = atan (50/0/100.0) = atan (0.5) = 26.5651
Then to cover the full horizontal FOV, simply multiply by two.

02 February 2009, 09:51 AM
An easy way to think of it is this: if you set camera FOV to 90, the width of the view will be target distance * 2

02 February 2009, 02:57 AM
ok cheers guys, this is handy to know :)

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