Carl Persson has recently become a major player in the Doom source editing scene with the release of some incredible screenshots showing off Quake-like lightsourcing and dynamic lighting. Persson originally created an underrated source port known as "Doom+" but recently has teamed up with the Doom Legacy team to bring the Doom community some new and incredible effects.

Doomworld: What was your first foray into the world of Doom source editing?

Carl: I first got the news of Id's public licence release in mid January '98, downloaded it and started Doom+, the earlier port I was doing. Doom+ was later discontinued due to that I thought it would be better to team up with someone else, and my eyes fell on Doom Legacy. And I still think it's the best. ;^)

Doomworld: Did you play Doom much before the source was released?

Carl: Sure, I've played it on and off ever since the first version came out sometime back in the middle ages, but I've never been what you'd call a good player. I'm a happy amateur.

Doomworld: Enough with the personal crap, we just care about those cool screenshots :) What made you attempt to add lightsourcing to Doom?

Carl: Well the major spur is that I think the Doom series have better atmosphere and immersiveness than Quake, so I thought it would be cool if someone could bring Doom a bit closer to today's standards.

Doomworld: How easy did adding lightsourcing turn out to be?

Carl: Hmm, that question is almost impossible to answer. I've been into demo coding and some hobby games programming, so I had an idea of how to do it, and it was quite straight-forward from there.

Doomworld: How long did it take?

Carl: The test version of the dynamic lighting you see in the first screenshots took about two or three nights from scratch. But it's far from finished, and it will take a long time to get from here to release quality.

Doomworld: I am assuming that the current WAD format didn't allow you to add in the lightsourcing and dynamic lighting, but I could be wrong. Did you have to alter the WAD format in any way to acheive this effect?

Carl: Actually the dynamic lighting doesn't need anything stored in the WAD, so any level can be used for that. The static, precalculated lighting generated from DLight is another issue, and it will probably be stored in an extra lump along with the other level data. There will possibly be an option to store it in a separate WAD file too.

Doomworld: How much larger filesize-wise would a level lit with this technique be compared to a level lit with standard sector-based lighting?

Carl: That's very hard to say, it all depends on how large the wall and floor areas are in the level. An example, for MAP01 in Doom2 it takes about as much space as the level, but that's excluding the floors and ceilings. And with colored lighting you can double that size. If size tends to be disturbing, we might implement a compression scheme of some kind.

Doomworld: Flats are apparently not yet affected by the lightsourcing. Why not? Do flats provide a particular problem?

Carl: To answer your first question, they're not there because I did the walls first. =) The flats are different, and might take a little time to get working good, but they'll be in.

Doomworld: Any plans to allow linedefs to trigger lightsources?

Carl: Yeah, there are some issues with the sector light FX that Doom supports. It will probably be solved by storing two or more versions of all lightmaps that are affected by the special effect, and simply switching them when needed.

Doomworld: Do you plan to make this code publicly availabkle?

Carl: Well, I haven't discussed it with Fab and Boris yet, but it will probably be allright. Sean White has asked to have it in Thrust, and I see no problems as long as they state the original authors where applicable.

Doomworld: How adjustable will the lightsources be? Will a dynamic lightsource be tunable for things like intensity and reach? How about pulsating or flickering lightsources?

Carl: The dynamic lightsources will be able to do many tricks, including the ones you mention. Combined with the planned scripting support of Legacy it could be quite flexible.

Doomworld: Is colored lightsourcing a possibility?

Carl: Definitely!

Doomworld: How specialized and/or advanced do you forsee this type of lighting being able to reach within Doom? Do you predict one day to see Unreal-like lighting (in terms of customizability) within Doom?

Carl: I'm embarrassed to say that I don't know much about Unreal other than that I think it is great. I haven't reflected much yet on the technical aspects. But as far as Doom goes there should be no limit other than what is set by the allowed level geometry. Actually, some of the Doom limitations can be an asset in terms of speed and features.

Doomworld: The editor to create the lightmaps is called DLight. What is this editor like? Does it basically place lightsourcing Things within the map?

Carl: It's a command line utility that is planned to be able to light an entire level smoothly using only the sector light levels. But this needs more testing. Additionally, you'll be able to place freely placeable lightsources anywhere in 3D space, and you will also be able to make Things emit light. Useful for candles, lamps and various items. This will probably be made possible with an ASCII script file, that can be editable manually or output along with the level from a level editor.

Doomworld: Do you think that this sort of lightsourcing will ever make the standard sector-based lighting obsolete in Doom?

Carl: Why not? I think it's a matter of taste, some people still prefer the original Doom than the new "ports". Technically speaking, yes. As long as the framerate is good enough there's no reason to stick with the old lighting system.

Doomworld: What are some of your future plans for Doom hacking besides this new lightsourcing?

Carl: One feature that comes for free with the lighting system is that we can make permanent blurred "specks" on surfaces. This could mean blood pools and trails, soot from weapon hits and more. Another thing that is certainly possible is bump mapping, which might look quite good along with the lighting.

The screenshots look cool, and seeing as that's the result of only a few nights of work, we can only imagine what the finished product will be! Be sure and keep a lookout for Doom Legacy, complete with lighting which may turn out to eclipse even Quake's! (One can dream, can't they?)

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