Unreal Engine's software texture dithering

Went back and checked how the Unreal Engine 1 games look software rendered and found that it's a pretty interesting topic. I remember they made a big deal of Unreal's software mode at the time because it wasn't gutted of its graphical effects like other 3D accelerated games at the time, like Quake 2. I noticed that the textures in the environment are processed with some type of dithering to "smooth" them out, in a crude type of way. I also managed to disable this in the .ini to see what it looks like without it.

You can compare these two images with and without the dithering, which I took from Unreal Tournament:

Dither on
Dither off

Are there any other games at all (besides Unreal based ones, so no Deus Ex!) that use this?

Looks much better with the dithering off. It's a lot sharper

I don't know of any other game that does that trick.

Apparently it's a very simple algorithm but I'm not sure just how CPU-intensive it is. Perhaps there's some odd PS1 game out there that attempts to use this to mask some of the blatant pixelation.

Here are some more screenshots I took to highlight this distinct look

http://abload.de/img/unreal014pur9.jpg
http://abload.de/img/unreal04aiubv.jpg
http://abload.de/img/ut04uuj5l.jpg

It only seems to apply to the basic world geometry. Character & weapon models or specific objects aren't affected.

Shouldn't be that CPU intensive, just a slight change in the way it chooses which pixel from a texture to draw when it's rendering it.

It's pretty neat I gotta say, a cheap way to get texture filtering. Unfortunately, much like the N64, it might as well have giant pixels since they end up looking better :p.

That's impressive. And for the time, at a lower resolution and a CRT monitor. You probably wouldn't notice much a difference between the dither and gl filter. Until you walk right up to the wall. But hey, if you didn't have a high end video card, this would probably be pretty nice!

The point of dithering at the time was that TVs couldn't show such a high resolution (even some computer monitors for that matter), so the dithering blurred to make for more color. The PSX has a global dither enable that many games used to make the 15-bit RGB output look better (more even color gradients).

Ugh, that PS1 dithering shows up bad in component. The N64 also had some really ugly dithering.

Quote:

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Originally Posted by old man

Ugh, that PS1 dithering shows up bad in component. The N64 also had some really ugly dithering.

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Yes, the better the input and TV, the worse it looks. Dithering is meant for composite/RF input on mainstream (for the time) TVs. The lower quality the input, the better dithering worked.