Doom 1 + Doom 2 wad

Since Doom 1 and Doom 2 has differently named map lumps, is it possible to create a Doom 1 megawad, in addition to the MAP01-MAP32 Doom 2 levels making a full 4 Episode Doom 1 megawad plus the elongated "5th episode" being the Doom 2 portion in a single super-megawad?

Basically how plausible is it that you'd be required to play the first four episodes with Doom 1, then switch to Doom 2 for the fifth bonus episode using a single wad? What obstacles might I run into if I were to do this?

You might run into problems with textures, unless you include all of the textures unique to either game in your wad. I'm not sure how different ports will handle the need to define all the textures, though, if you do so without actually including all their patch lumps; some might have no problem unless they're used in a map, others might choke on the PNAMES or TEXTURE1 lump entirely?

EDGE actually supports Doom 2 as a fifth episode out of the box, so I think your megawad would work fine without any additional work. ZDoom and Eternity* could definitely handle doing it too, but like essel said you'd probably need to include custom PNAMES and TEXTUREX lumps with all of the patches and textures for both games listed. No idea about other ports.

*I ran into some issues with trying to make Doom 1 a single episode in Eternity, but I'm pretty sure they've all been cleared up now.

You could solve what essel noted by requiring both IWADs regardless of the game played, merging texture definitions in the PWAD. The more advanced ports (at least ZDoom and I think Eternity) added a way to define WADs to load automatically, which would save the player from having to add the other IWAD in the command line, which is still an option for engines that don't have the feature.

I would like to see HeXen to be the next episode in Heretic.

Also add Final Doom and the Master Levels. Then do it all in ONE HUGE MARATHON

Then tell us the time it took to finish it, since ZDoom/GZDoom and probably others tracks this stuff :D

Ragnor said:

Also add Final Doom and the Master Levels. Then do it all in ONE HUGE MARATHON

Would be nice, and a nightmare to set up. Are there any ports that'll support more than 99 maps in a wad - or is it all in the way they're named?

Johnny, you genius!
It had also crossed my mind some days earlier. As I was planning to make my planned wad Ultimate Showdown, soon I was willing to do not less than 68 maps! So, both IWADS (not including TNT and Plutonia, of course) can make the wad run, and I'm even up for a bugfix if something goes wrong. Nothing else...

GreyGhost said:

Would be nice, and a nightmare to set up. Are there any ports that'll support more than 99 maps in a wad - or is it all in the way they're named?

There is no hard limit to the number of maps you could set up in ZDoom, with MAPINFO, since you don't have to follow ExMy or MAPzz conventions -- you could name them from 0 to ZZZZZZZZ, for example, and that'd be 36^8+36^7+36^5+36^4+36^3+36^2+36 names possible. (There's actually more than that since you can use non-alphanumeric characters like - or _, too.)

You can use final doom too? The map lumpnames are the same though right?