OpenNova. Rebuilding a classic Mac OS game.

A few months ago I decided to undertake a slightly ludicrous side project. To re-implement a modern version of the classic Mac OS game, Escape Velocity Nova. The game is at this point essentially abandoned. Ambrosia Software is but a ghost of shell of their former selves and the game receives very little in the way of support. Furthermore it also relies on technologies from the Classic Macintosh days such as ResourceForks, QuickDraw and various others. Apple are advancing macOS each year and its becoming apparent that a lot of the old classic games are at the end of their lives.

EV Nova already requires an unofficial patch (or tweaking of the application binary) to run on systems later than macOS 10.11. Sooner or later, Apple is going to deliver the final nail to the coffin.

This is where my idea was spawned. I had once been a member of the community for EV Nova (particularly on ev-nova.net). I loved the game and would play it constantly. I was much younger at the time (true for everyone, unless you’re Benjamin Button) and had just started to really learn how to develop software. I decided to try my hand at creating a plugin development tool for EV Nova. The tool I made was crap, but it gave me insight into how the game worked. So, drawing upon nostalgia and old knowledge of the game I decided that rebuilding the game engine, with modern technologies, was the only solution.

This presented a slight problem…

ResourceForks & HFS+

With the release of Mac OS X almost 17 years ago, Apple declared that the ResourceFork was “legacy” technology and should no longer be used for new projects. However the API’s were still present for old programs. Great!

With the migration to 64-bit, Apple declared that the Carbon framework was now deprecated and end-of-life. The Carbon framework is where the ResourceFork functionality lives/lived. Uh-oh.

As Apple continued marching onwards the ResourceFork became less and less reliable. EV Nova received an update to deal with this. They migrated all the data files over to the ndat format. ndat is nothing special. It’s simply the ResourceFork data in a simple DataFork file. However the contents are a proprietary Apple format. No problem, the old Carbon functions could parse it. They maybe deprecated but they weren’t going anywhere anytime soon!

But it poses a problem. The old Carbon frameworks will be thrown out at some point. And when they are EV Nova will stop working. Those frameworks are the only part of Apple’s systems that can read the old ResourceFork format.

Now it’s true that the windows version doesn’t use the ndat format. It uses a custom rez format. So in theory that functionality could be moved over to the Mac version. But that would be a huge undertaking, and given the state of Ambrosia Software these days, probably not very likely.

So there is only one future proof solution… make a custom implementation of the parser for the ndat format (and one for rez at the same time).

QuickDraw

Awesome! We’re going to be up and running in no time! We’ll have all the old resources extracted out and we’ll be able to start building a game engine.

Uh-oh! Turns out resources such as PICT, cicn, RLË, ppät, etc, were all encoded/decoded via QuickDraw functionality, and that has long since gone the way of the dodo on macOS. Though curiously Preview can still render a PICT? Either way there is no publicly available way to handle those resources.

So that means a need to reverse engineer those as well… this may take a while.

A slight hint of a silver lining

There is some good that will come out of this project.

1. It will hopefully result in a modern version of the game engine that will continue to work for years to come.
2. Old total conversions such as Polycon EV, and even the Escape Velocity, and Escape Velocity Override conversions will work in this new engine with modification to the files.
3. It’s modern and will have custom parsers included so it wouldn’t be too much a stretch to get it running on iOS (though controls maybe an issue.)

I plan on using the blog to keep people who are interested up to date with the progress of work and to document some of the technical aspects as well.

Hopefully this will be of interest to some people…