Talk:Aspect ratio

This is all theory and unsourced. You can't use this for evidence of anything. 68.126.1.159 22:38, 14 June 2007 (UTC)

Latest diagrams
The latest diagrams seem somewhat confused, Image:Aspect diagram.png, for example. The point is that in the 320x200 VGA mode, pixels aren't square: 320x200 should fill the whole screen, even though the sides of the monitor are always in a 4:3 ratio, the actual screen resolution that the game outputs to is a 16:10 ratio. If you run Vanilla Doom and take a screenshot, viewing that screenshot back in Windows in 1024x768 resolution, the screenshot will appear squashed.

I don't know if perhaps I'm not understanding the purpose of this diagram. I might not be seeing the point you're trying to make. The whole point of the aspect ratio thing is that when you run in 320x200, there shouldn't be any black borders at the top and bottom of the screen: it should fill the whole screen. Fraggle 23:43, 17 June 2007 (UTC)
 * Yeah, I'm not talking about that specifically, just aspect ratios in general. The first diagram is to clarify what I think you said about Doom 95, since it's not worded well. The second is to demonstrate how some ports don't correctly manage different aspects. Like I was saying about Skulltag, they don't swap between 4:3 and 16:10 correctly. Which one is right isn't as important as the fact that one of them has to be wrong. Tangent 23:48, 17 June 2007 (UTC)
 * I think you've confused the issue by talking about widescreen modes. Can we stick to discussion of "normal" (4:3 size ratio) monitors?  Or is the entire problem you're having caused by your use of a widescreen monitor? Fraggle 00:08, 18 June 2007 (UTC)

From first principles
I'm going to lay out my entire point of view here, because I really think we're at crossed wavelengths and need to better understand each others' points.

Almost all monitors have a 4:3 ratio between the screen's physical width and height (although this is not true with a widescreen monitor). Vanilla Doom runs in the VGA 320x200 screen mode. So there is a difference between the 16:10 ratio of the screen mode and the 4:3 physical ratio of the monitor. You can solve this problem in two ways:


 * 1) Scale the image up to the screen, leaving black borders at the top and the bottom of the screen ("letterboxing").  If you do this, the pixels stay square.
 * 2) Stretch the image vertically to fill the entire screen.  If you do this, the pixels are no longer square, as they are now each taller than they are wide.

I am specifically stating that, as far as Doom is concerned, the second of these is the correct thing to do, because the graphics appear to have been designed for the VGA cards of that era, and this is what those cards did. If you do the first option, and use borders, the screen image will appear squashed (like in Image:Aspect-ratio-titlepic.png). Some modern graphics cards only support 4:3 screen modes through the borders method: this is why I included the section on choosing a video card, because if you want Doom to run as it was natively designed to run (without borders), then you want a card that does the second option, rather than the first.

What aspect ratio correction does is to perform the stretching in software, because we can no longer rely on consistent behaviour across graphics cards and monitors. The game runs in a 4:3 screen mode (like 320x240, 640x480) and is stretched in software to appear as it would have originally appeared on a DOS VGA machine in 1993.

If you're going to run on a widescreen monitor, it becomes more complicated. Now, you effectively have extra space at the left and the right sides of the screens. In this case, you can either:


 * 1) Display black borders at the left and right side of the screen (ie. not use the extra space)
 * 2) Expand the rendered field of view so that you can horizontally see more.

Now, you can shoot yourself in the foot here, because there is another option: you can stretch the screen out horizontally to fill the extra space. But then you've screwed the aspect ratio again and squashed the screen again (back to looking like Image:Aspect-ratio-titlepic.png). So the correct thing to do is always one of the above two options.

How does this tie in to your thoughts? Fraggle 00:16, 18 June 2007 (UTC)