Understanding FOV

Posted by FZD School of Design via YouTube is an informative and easy to understand two-part tutorial on the technical breakdown of how Field of View (FOV) is implemented in video games.  More importantly, the presentation goes into detail as to why poor FOV in PC games can be a major distraction to the player.

Part 1:


Part 2:

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10 thoughts on “Understanding FOV

  1. To clarify one thing…
    Camera has a flat sensor
    Eye has a wrap-around retina (i.e. spanning from the back of the eye, up towards the sides of the eye)
    Given the same shape lens, the eye can detect a more oblique light ray, as the ray strikes the retina portion along the side of the eye.
    If you were to ‘flatten’ the retina to match a camera photo sensor, then the eye’s lens would become more round to allow for the same oblique angle coverage.
    Also, games have a flat projection, where the eye has a spherical projection.

    To simulate the eye’s vision, in regards to image projection, a game would have to divide coordinates by sqrt(dx^2+dy^2+dz^2) (true distance) when going from 3d to 2d.
    However, games divide by simply dz (distance along the normal of the camera).
    This leads to a limit of < 180 degrees FOV, as z distance is normal to the camera direction. 90 degrees off center is a discontinuity, and over 90 is invalid.
    Also, because 90-off-center approaches a limit, locations on screen which exist near 90-off-center become distorted (in the sense that small angles near the edges of the screen occupy a lot of screen space, but small angles near the center of the screen occupy a small amount of screen space, it's not consistent, hence an appearance of skew.).

    A neat approximation of the eye's vision would be to partition the FOV into a set of smaller FOVs stitched together, with each small FOV being rendered with the camera looking down the center of that fov. IIRC An old quake(1) mod did this.


  2. Great video, this is one the things I’ve always understood, but often don’t really bother to try and explain to other people because I’ve never really known how to correctly. Thanks for the share.

    • FOV is something most big budget studios always seem to miss. It does not matter if the game allows for widescreen resolutions, if the FOV is not correct, it does not matter in the end.

  3. I’m not sure it would be possible for those videos to make the explanation any more overly complicated. Its as if they’re deliberately over complicating something which is very simple just so it seems like they can teach you about these things.

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