because that definition doesn't include what we often use it for - in that it's also the designed or intended AR/FOV.
Why would the baseline NOT be the intended AR/FOV? Someone explicitly programmed a 4:3 aspect ratio. The code would have looked something like this:
V-FOV = 75
H-FOV = 90
If AR > 4/3 then reduce V-FOV accordingly
And post-patch, the only thing that changed was the last line, to this:
If AR > 4/3 then increase H-FOV accordingly
If we assume that the original 16:9 behavior was correct, that means the default V-FOV value is deliberately too high. Why would anyone program it that way? It doesn't make any sense, and it isn't intuitive.
With the case of Bioshock, just because 4:3 stayed the same before and after the patch, that might make it the new baseline, HOWEVER it doesn't necessarily make it the new intended AR/FOV.
It's just about the only solid evidence we've got as to the intended AR/FOV. As you say, they are usually/traditionally the same thing. As I say, it doesn't make any sense for these things to be different.
I'd like to point out it's even simpler than that. The developer will either actually have to go out of its way to make the behavior vert- or simply not program the equation for the view frustum correctly. Correctly calculating a view frustum involves keeping the
vertical FOV constant with the aspect ratio being the variable that determines the
horizontal FOV. The corner points for the frustum will thus be different for the same field of view if the aspect ratio is larger, adding more viewable space horizontally while the vertical viewing space stays the same. In other words the equation for the frustum needs to be recalculated to make the hFOV constant and the vFOV variable
If you know linear algebra the equation of the perspective matrix is thus:
Code:
|cot(fovy/2)/AR, 0 , 0 , 0 |
|0 , cot(fovy/2), 0 , 0 |
|0 , 0 , (zFar+zNear)/(zNear-zFar), 2(zFar*zNear)/(zNear-zFar)|
|0 , 0 , -1 , 0 |
Aspect ratios are width:height. Someone posted earlier showing equivalent ratios. 4:3=12:9. You can easily see comparing this number to 16:9 that 16 > 12 while 9 == 9. In other words the direct comparable resolutions would be 1600x1200 and 1920x1200. This means that hFOV should change based on the aspect ratio while vFOV stays the same. So a 4:3 screen should be seeing less horizontally than a 16:9 screen when the code is implemented correctly. Meaning if a game is "aspect centric" to 16:9 then a 4:3 screen should not be seeing more vertically, but should be seeing less horizontally.
I'm a single screen user and I believe that, not only is it ideal, but it is natural that screen change behavior should be hor+.
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