1. You get that, because you have very, very wide screen that covers not only what you see in front of you, but also on both sides, which has been flattened.
I understand what you're saying regarding 180° views (or close to it) because you can't project that onto a flat surface and have it make sense. Hopefully we've not been arguing that point, because we agree... however, when talking about a 'normal' screen, as wide as 16:9, and 'high' FOV up to, say, 80°, you don't get that close to 180° horizontal FOV. That particular example would be around 142°, which would be difficult to manage, but not impossible... and I think it's a little extreme for most people anyway (personally I have my vertical FOV set to 60° on my 16:9 screen).
To help illustrate the 'perspective' correction, and altering, that happens with screen size and/or distance to screen, I've put together a few crudely drawn diagrams. We have slightly hijacked the thread here, but hopefully these will actually help illustrate what ZeosPantera is hoping to achieve (and avoid) with the whole FOV calculation he's detailed.
First, to set the scene:
What we have here is the viewer on the left, looking at a screen which the game will draw the in-game objects on; in this case I've kept things simple and have provided 4 in-game objects, all approximately equal distance from the viewer in the game. You can see the FOV formed by the distance from the viewer to the screen, and the size of the screen. In this case I've assumed the game has been set up correctly as per ZeosPantera's calculations, so the in-game FOV matches the true (real) FOV. (this could be either a top view or a side view - it doesn't really matter as the concept is the same)
Now, let's illustrate the way the visible objects are drawn on screen:
Here I've just traced from both sides of the visible objects back to the viewer, showing where the objects extents will appear on screen. It is quite obvious from this diagram that when the virtual and real FOVs match, the viewer will perceive the objects to be in the correct position and of the correct size - just as if they were real objects and sitting the same distance away in the real world. This is the whole objective of this thread.
Now, the reason games don't have this setting by default is that, as you can tell, the FOV isn't very big.. which limits how much stuff you can see in the game. In this case we can't see the red objects at all - in rFactor they might be cars that are actually slightly ahead of us, but we don't see them at all because the FOV is so limited.
I believe this was what Tim was referring to when he said he wouldn't go below 60° FOV - not because it's not realistic (perspective-wise) but because you severely limit your visibility when you cut down your angles that much on a normal screen.
So, like every other mainstream game, rFactor defaults to a larger FOV, allowing you to see more of the game-world... like so:
Ah, that's better. Now we can see all the objects... but wait. Look at where the object extents hit the screen, and the size of them from the viewer's position. The red objects are much wider than the green - the change in FOV has warped the image, giving the 'stretching' near the edges. It's an unavoidable side effect of viewing an image with a lower FOV than that which it captures - and it does happen with photos you have in front of you, and most TV you watch, which is perhaps part of the reason we don't really notice it so much when we're playing games. Mind you, some people do get nauseous when watching/playing games, and I think this is a large part of the reason.
So, this is a high-FOV image viewed on a small screen from a 'small' distance, or on a large screen viewed from a large distance (obviously you could scale this diagram to any size you want, the same effect will be apparent).
Finally, we ask: what happens if we keep the same screen size, and same image, but move closer to it?
Now, perhaps, it is clear why I keep saying you need a big image/screen. Getting a high-FOV image 'correct' with a normal size screen will not end well - you'll be so close you can't focus on the image at all, plus the fact you have 2 eyes an appreciable distance apart (in the context) will makes things even more confusing.
However, given a large enough screen to make getting this close comfortable, the perspective will make sense.
There is an important distinction here: if you look at the screen, the objects are drawn on it at different sizes, just like they were before. The red ones definitely use up more screen area, more pixels, than the green ones.
The key is that from
the viewer's position, and perspective, they appear the same size.
One final point: I'll happily admit this is an extreme example. But given the limited scale of my poor little drawings it helps to show the difference. When you're viewing the screen, especially moving around nearby objects, even a fairly small discrepancy in FOV is quite apparent.
So, this is what I've been trying to explain without a lot of success. The stretching that occurs at the screen edges (well, across the whole image really, but it gets worse and much more obvious at the edges) can be offset by the foreshortening that occurs from the viewer's perspective.
You can see in the diagram above that the central part of the screen, where the green objects are drawn, is not at much of an angle to the viewer. Conversely, out near the edges the angle is quite acute - which will appear to shrink the stretched image at that point, so it comes out the correct size. (if green and red were the same size on the screen, the red ones would look smaller because of the screen angle)
I sincerely hope this all makes sense now
