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I understand the following.

1) ViewPort: It is like a window through which one can see the outside world. Basically, it is a 2D plane on which 3D objects gets projected.

2) Field Of View (FOV): FOV is a cone projection from the eye pupil or virtual camera. One can see everything inside that cone projection without turning the head.

  • Monocular FOV is what a single eye can see

  • Binocular FOV is what both eyes put together can see clearly

  • Peripheral FOV is the region outside the binocular FOV but within monocular FOV.

My question is,

1) What is ViewPort and FOV in a virtual reality (VR) Headset device? What is the difference between them in that context?

MayurK
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1 Answers1

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ViewPort is what you describe. It's usually defined as bounds. Between 0.0 and 1.0 for both width and height, where 0.0 is the left-most edge of the screen. Less intuitively 0.0 is at the bottom of the screen (I guess this might vary between systems). Sometimes it's defined in screen pixels instead. Also, rather than absolute bounds, second parameters may be defined as extent instead.

Example:

Left viewport definition, bounds (0.0, 0.0, 0.5, 1.0) Means going from left/bottom corner, to center/top.

Right viewport definition, bounds (0.5, 0.0, 1.0, 1.0) Means going from center/bottom, to right/top.

Right viewport definition, extent (0.5, 0.0, 0.5, 1.0) Going from center/bottom, and extends half a screen horizontally, full screen vertically.

FOV is usually mentioned as the total field the user can see (counting both viewports in the case of VR). It's usually measured as an angle in degrees.

reden
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  • Thank you @reden! Could you please explain briefly what does 0.0-1.0 means in ViewPort? – MayurK Oct 13 '16 at 05:04
  • Please note, though; I'm trying to explain this from an engine-agnostic point of view. Unity3D may do things differently. – reden Oct 13 '16 at 06:52
  • I understood what you are explaining @reden, Thank you! So, If I have a 360 video, assume I have a metadata for FOV (part of video frame to be shown at an instance as dictated by video provider), do I need to fit that FOV inside ViewPort area? – MayurK Oct 13 '16 at 09:09
  • I think it's out of scope of the question. But I'm actually working on something like that right now, My approach is to leave the viewports as they are (half of the screen each). Instead I work with the texture coords of two quads I'm displaying the video on. I adjust the texture coords to show the approriate amount of video. (It's very much WIP) – reden Oct 13 '16 at 10:04
  • Yeah @reden. I opened a new question about this. Could you answer it? - http://stackoverflow.com/questions/40022375/how-to-handle-mismatch-between-vr-headset-fov-and-video-stream-fov – MayurK Oct 13 '16 at 13:30