I'm wondering if anyone know of any games where many of the game's resource files are well known and easy to implement loaders/parsers for given documentation. For example, Doom 3 or Quake would fit this description. Not because the code is open-source, but because the file formats are documented and available.

Reason for asking is that my idea of a fun project is to take the resources from an existing game and then try to load as much possible of it with a custom engine.

World Of Warcraft seems to have many of it's resources pretty well reverse engineered. Also probably most games that have engine source ports (also most games with decent mod SDKs) available will have at least some documentation on their assets, eg. Command & Conquer 1 & 2, Red Alert, etc. Warcraft 2, Serious Sam, all the Build engine games like Duke Nukem 3D, Blood, etc. Some others I can think of: Jedi Knight, all the Source engine games, Battlefield 1942.

I hope some of those suggestions are helpful/appealing, I'm sure there's plenty more too. =)

Thanks, Michael! WoW and Battlefield could be perfect if it also includes specs of the world and terrain assets. I was secretly hoping for something massive that would take at least some effort to hit 60 fps on a modern computer to render. Older and smaller games is fun too, but that would be more about the practice of resource loading than actually rendering it efficiently.

If anyone have any more suggestions, I'd appreciate that too. Massive or otherwise.

Check out OpenMW if you're into The Elder Scrolls.

Thanks, Jesse! Exactly the kind of project I would like to start myself - writing a replacement engine for a game. Contributing to OpenMW sounds like fun, too.

Edit: On second thought...

Install OpenMW dependencies:
OpenSceneGraph git libopenal-dev \
libsdl2-dev libqt4-dev libboost-filesystem-dev libboost-thread-dev \
libboost-program-options-dev libboost-system-dev \
libavcodec-dev libavformat-dev libavutil-dev libswscale-dev libswresample-dev \
libbullet-dev libmygui-dev libunshield-dev cmake build-essential \
libqt4-opengl-dev

I think I'll just stick with the resource documentation ;-)

Yeah, OpenMW has gone through a number of organizational changes which have all left their mark, unfortunately.

I've fantasized about doing this with The Sims (all of 4+ of them in one fancy new engine) for a long time, and there's plenty of source code and documentation available from mod tools last I looked.

As far as a more graphically intensive performance challenge goes, you could look into the Mass Effect series. ME3Explorer (the suite of mod tools that despite it's name actually supports all three games to varying degrees) is open source, and their wiki looks like it has at least good entry-level overviews of the formats involved (see http://me3explorer.wikia.com/wiki/Textures_in_Mass_Effect for example). You might need to look at their actual code for the details though, for all I know it could be an incomprehensible mess. But it's still an active project so you could probably get answers to any questions you had if you ask them. As a bonus, if you can master these asset formats you'll have one foot in the door to supporting innumerable other Unreal Engine games.

Any 3d Elder Scrolls or Fallout game is gonna have decent documentation buried somewhere under the thousands of of higher level modding tutorials, like here for example: http://www.uesp.net/wiki/Tes5Mod:File_Formats

Really though, google whatever games you'd be most exited about doing this to plus "file formats" or "mod tools" and see what you can find.

In a similar vein to OpenMW, you could also take a look at 0 AD, an open source Age of Empire's like game, which is looking pretty good now.

https://play0ad.com/