Pixel aspect ratio and HUDs

This article on Gamasutra mentions how difficult it is to get a proper image on old games via emulation, due to the use of non-square pixels. Even though I don’t emulate DOS games, I have the same problem, because my old computer is connected to an LCD screen. A crappy ancient 1024×768 screen, but an LCD nonetheless. This does give me some really good images when playing on 512×384 though. But not all DOS games supported that.

On a side note, it’s interesting how games are made to display the correct aspect ratio regardless of the resolution used. Some images taken directly from Quake show how this works:

The original. 320x200. Notice how squashed it is.
The original. 320×200. Notice how squashed it is.
Now on 320x240. This is the square pixels image.
Now on 320×240. This is the square pixels image.

One thing to notice. The 320×200 image (top) is clearly squashed, but the HUD is the same regardless. Now, on 320×240 the 3D space uses square pixels for the correct aspect ratio anyway, so it’s pretty obvious how the game is supposed to look like. But which is the proper aspect ratio for the HUD?

A quick run through Irfanview tells us that the HUD takes exactly a 320×48 space. This leaves us with 320×152 pixels of game space for the default resolution, and 320×192 if we can afford the slightly higher res. Now, take a look at the 320×240 image: you can see the whole top row of skulls on the right door, while the 320×200 image has only half a row.

So does the higher resolution give us slightly more space to look at? We can try and change the aspect ratio of the 320×200 image to 4:3 to find out.

320x200 (4:3)
320×200 (4:3)
Side to side! 320x240 (left), 320x200 stretched (right)
Side to side! 320×240 (left), 320×200 stretched (right)

Let’s blow that up to double resolution for our viewing pleasure!

320x200, zoomed up to 640x400. Resizing, not resampling.
320×200, zoomed up to 640×400. Resizing, not resampling.
320x200 stretched to 320x240, then zoomed up to 640x480.
320×200 stretched to 320×240, then zoomed up to 640×480.
320x240, zoomed up to 640x480. Notice any difference?
320×240, zoomed up to 640×480. Notice any difference?
Maybe now you do.
Maybe now you do.

The differences are subtle, but they are there.In other words, playing on 320×200 would show the correct aspect ratio, but 320×240 would do the same AND also give us a slightly higher vertical use of the image.

Still, if we look at the empty armor box, it’s also pretty obvious that the HUD is squashed in 320×240. So the devs specifically made it for 320×200. Strange.


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