Talk:Text Mode Doom


I'm digging out old screenshots in order to write this article. -- Jdowland 10:36, 19 Jun 2005 (UTC)

Lib caca Images[edit]

The second picture is Doom Legacy! Doomlegacylibcacmatch.png GhostlyDeath 10:15, 14 July 2008 (UTC)

smmu's textmode implementation[edit]

Fraggle, your original textmode smmu page had a really good detailed look at how you implemented the color-shifting, etc., which would be nice for this page. Do you still have it? Either way, would you grant a licence on the material so that we could use it in this article? I can probably find it.

Note that the three SMMU pics there I think I took in the first place, but I found them on a page which had mirrored some of your old page. I remember there were two tiers of shots, those from before and those from after you implemented background dithering.

I'm building a win95 box in order to actually run SMMU/DOS and take some proper shots :-)

-- Jdowland 21:31, 20 Jun 2005 (UTC)

I've lost the original page and images I had, unfortunately.

The system works by using the extended ASCII text mode "gradient" characters (there are ~4-5 of them). When the palette is set, the hue and brightness of each colour is calculated from the palette entries. The hue is then used to select the text-mode colour to use for the character, while the brightness is used to select the character to use.

The extended mode ascii characters used are (descriptions I think are correct):

  • "space" character (32): all background
  • 0xb0: 20% foreground
  • 0xb1: 40% foreground
  • 0xb2: 60% foreground
  • 0xdb: 80% foreground

The original version of the SMMU textmode renderer used black as the background, and the selected colour as the foreground (ie, 5 steps). I later improved on it by adding greater colour depth and using the background colour. Basically text mode has two sets of colours; the second are the same as the first but brighter (1 is blue, 9 is "bright blue"). So instead of going from black -> colour, I made it go black -> colour -> bright colour (the first stage having black background + colour foreground, the second stage having colour background + bright colour foreground). This effectively doubles the colour depth.

Fraggle 08:20, 21 Jun 2005 (UTC)