A total conversion for GZdoom of the Atari Jaguar classic Alien vs Predator.

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What the hell is this?

When I was young (so much younger than today), my fondest Christmas memory was getting a little-known, little-owned game system: the Atari Jaguar. Oh man, was that awesome.

The first games I ever got were a Gouraud-shaded polygonal 3D shooter, Cybermorph, and the remade version of Wolfenstein 3D. Good times were had.

But, one of the true classics of the system, and arguably gaming in general, was Alien vs Predator. Tapping into some of the more special features of the Jaguar at the time–very special when compared to the systems out at the time, the Genesis and SNES among them–the AvP had photo-realistic graphics, a dark atmosphere, and nasty, nasty enemies roaming a complex set of hub-like levels which you’d visit again and again on your trek. Not to mention the three character classes: Marine, Predator, Alien. Each had a completely different playstyle and goal, but in the same levels.

Of course, there were problems. A shoddy frame-rate due to Atari’s limits on what developers could use the processors for (some devs ignored the rules, and their games run at a slippy-quick 60fps). A crappy save system due to very limited space on the cartridge (OMG, remember those?) which had somewhere around 256 byte…bytes, folks, not kilobytes or megabytes…of storage space, meaning all they could save was your player class, location, and weapons/ammo/keys, and all enemies and items would respawn upon loading.

And that’s where this project comes in.

What is this project, already!

I am recreating the gameplay and features of the Jaguar game, AvP, in GZdoom. GZDoom is an advanced source-port of the Doom engine, allowing OpenGL graphics, scripting, new features, etc.

This is no easy feat, but not the most difficult either. Both the original Doom and AvP are FPS games, both from the same era of gaming, both with similar resolution and functions. The gameplay is quite different, of course, with AvP being a more tactical, slower paced, maze-like game that was a survival-horror game before that genre even existed. But, in the end, they are as similar as they are different.

But AvP did things very different than Doom. Doom has 3D doors that have a thickness to them, AvP used a sort of 0-pixel deep “wall that could open” kind of door. Things like that.

Project goals:

  • Recreate the terror, survival-horror, FPS elements of AvP
  • Use as many of the original graphics as possible
  • By doing so in GZDoom, bring this classic back to life in a way anyone can play with a much better framerate and save system.
  • Once this “vanilla” version of the game has been ported, duplicate the levels and have a 2nd episode, a “game+” version, that adds new features, reduces the map’s “sameness,” taps into dynamic lighting and alt-fire modes, etc.

Development cycle:


  • Recreate sublevel 3, the starting point for the marine, while massaging the gameplay elements needed for that class, like custom doors (GZDoom does not support the kind of 0-pixel deep sliding doors AvP uses) and weapons.
  • Recreate the Predator ship, the starting point for (you guessed it) the Predator, massaging the gameplay elements for that class, including cloaking, weapons, marine enemies, etc.
  • Recreate the Alien ship, the starting point for the (wait for it…) Alien, massaging the gameplay elements for that class, including the ability to plant chestbursters into enemies (extra lives) and the speed-based, pure melee gameplay of the Alien.
  • With the 3 classes done, and their respective weapons, items, and powers finished, duplicate the maps for sublevels 1, 2, 4, and 5, plus airducts. At this point, most items and enemies and class abilities would be finished, making most of the rest of the steps purely a clean-up operation linking everything together.
  • Game+


  • Duplicate the existing, tested, functional vanilla elements into a game+ mode.
  • Level pass: new textures, darker areas, broken lights, dynamic lights, secrets, supply caches that need password/keycard, etc. Basially, vanilla levels if they were made today in a more modern 2.5D engine.
  • Actor pass: new features, secondary fire weapons, Alien enemies on the walls/ceiling, etc. Every feature counterbalanced by an equal new feature on the other end, i.e., an alt-fire grenade launcher on the pulse rifle for the marine means an upgrade to Alien enemies to keep the balance.
  • Extra goodies pass: Alien blood that sizzles and disappears (making the corpse safe to walk by), but where does it go? Down a sublevel, obviously! Meaning acid dripping from ceilings a level below where you whacked that Alien, for a duration. Etc.
  • The goal here is to keep balance while adding features and ambience befitting a modern port of the game.

GZDoom vs ZDoom:

As it stands, this is a GZDoom only mod. Why? Well, ZDoom uses a software renderer that replicated classic Doom graphics very well, even to the limited texture color palette. Doom used 8-bit, 256 color max, textures. AvP uses 16-bit high-color textures. I MAY, maybe, MAY, could possibly, MAYBE, make it work via converting the AvP textures down to 8-bit, and release a ZDoom version, but I wouldn’t do that until the project is complete either way. Running this mod in ZDoom looks pretty bad, as the textures get the splotchy, bandy look of a high-color image dropped down to an 8-bit image.

But, we’ll see. Feel free to comment on your feels.

What may change:

GZDoom is not AvP. While it allows some very deep and advanced scripting in-engine, some things are more limited. For example, there is no way for me to add the Predator vision modes exactly as the Jaguar version had them.

The goal is to simulate/emulate/recreate the experience. Not to make a pixel-perfect version. In the above example, the vision modes would be simulated through some GZDoom trickery that would have the same effect, if not the exact same look.

An example is the enemy and weapon sprites. While some enterprising and talented Atari-nerds over at an Atari-Age forum helped me retrieve the textures from the game ROM, the enemies and animations have remained elusive. This means I’ll likely be using sprites from other Alien Doom TCs.

Another example is enemy respawn. The crap-assed save system had a perk: the game was never boring, or safe. You reloaded, and now the map was crawling with baddies. GZDoom, however, saves everything, including dead enemies. This means I need to code scripts to respawn enemies at random, in realistic, not too overwhelming, intervals.

But the goal remains: recreate the game in every way possible. Three shotgun shots kill an alien. The Predator can cloak and gains weapons by earning “points” via killing while uncloaked (honor), the Alien is fast as hell and “respawns” after death if the player planted a few chestbursters in some unfortunate marines. Etc.

Finally, for those who’ve never played the Jaguar AvP, a primer:

AvP on the Jaguar was a FPS/survival horror game. There were 3 parts to it, loosely grouped into easy (though not really easy), medium, and hard.

Predator: “Easy”(ish) - Weapons are earned, not found. Can cloak to avoid detection, decloak, slaughter, recloak (Aliens see you even if cloaked, so not a godmode feature except against humans). Can carry health with him, allowing for healing at any time as long as he carried some health packs (think of the scene in the movie where he heals via the device on his arm). No keys needed. Start in the ship, slaughter the way to the Alien ship, kill the queen.

Human: “Medium” - Start in the middle level of the station. Limited ammo. Need to find weapons and keys. Can heal, but like other FPS games, it is by getting health packs and is immediate, and cannot be carried for later. Levels become an enemy of a sort, due to jammed doors and mazelike air shafts. Read computer terminals to get hints and story. No “quest log” or guidance besides what you read and find.

Alien: “Hard” - Melee only. No healing. No use of items or objects. Need to always be on the move. Can respawn via cocooned marines. Cannot cocoon Predators, so fighting them become very dangerous instead of a possible way to extend your life. Respawn happens at oldest cocoon, meaning you may be set back a while when respawning. Start in Alien ship, get to Predator ship, free queen.

The “medium” and “hard” may swap places simply due to the better framerate of GZDoom. The Alien was difficult to play being fast and the game running at somewhere around 18 frames per second. Frankly, the marine is a harder campaign, as you have to explore the whole station with limited resources, but I always found the Alien harder to survive with. Die without a cocoon, and it’s GAME OVER MAN, GAME OVER! But with a better framerate and mouse/keyboard controls, who knows, the Alien may be the medium or even easy mode to play.

Things to love about the game:

  • 3 classes, lots of replay value.
  • Randomly placed enemies.
  • Limited resources means one has to plan and work hard to survive.
  • No guidance for the marine save for what you find in computer logs, so it’s very immersive.
  • A dark and menacing environment.

Things that need to be changed:

  • Save system (already fixed just by being in GZDoom)
  • Mapping system (same as above)
  • Framerate (hey, holy cow, same as above)
  • Tweaks for the game+ mode, like Alien acid-blood spills eating away at the floor and disappearing rather than staying forever to hurt you every time you try and pass the corpse in the thin hallways. (Vanilla will retain these elements, as that’s the whole point of vanilla)

And, really, finally now:

The internet is filled with pipe-dreams and half-finished projects. This will not be one of them. I am an experienced Doom modder, starting way back when direct-executable modifications were the only way to mod. I know Photoshop and Gimp, how to code, game design, AvP itself, and have a realistic plan.

And plenty of booze to see me through the trials and tribulations.

In fact, I have the first portion of the marine starting area complete already, and a git repository filled with R&D steps where I’m learning the hacks I’ll need to make this work (like those damned doors, which are hacky, scripted lines rather than classic Doom doors).

Leave me some comments and cheer me along, as I hope to be releasing playtest demos in beta form ASAP.

Comments  (0 - 10 of 21)
Guest - - 693,043 comments

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plazma82 - - 71 comments

how can i get the data off the jaguar cartridge

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Unknown_Horse - - 42 comments

i know this is dead, but i just wanted to say that i like the beatles reference.

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PippeGamesYT - - 23 comments

c'mon release this mod please

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Plazma_Fire - - 27 comments

5 years ago. i don't think this will happen or it might be a troll

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Guest - - 693,043 comments

Oh my god! I need this to breathe!!!

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Slayer12345 - - 2 comments

Really hope this project gets done one of my favourite games from 90's :)

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DENISN1NJA - - 9 comments

i am waiting for the full release of this great project.

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