What Went Right

Going beyond a port. Without an emulator, huge chunks of the game had to be discarded. The original rendering code of the game was very well suited to its original platform, but was entirely unusable on the Xbox 360. MacOS’s proprietary graphics API, QuickDraw, was used extensively throughout; some of its features, such as drawing 2D lines, were absent from the 360 entirely. Screen-space arithmetic was done using fixed-point integer math, a crucial optimization a decade ago but a source of needless complexity today.

Texture mapping was done using blocks of PowerPC and 68K assembler -- no one on the team was able to directly read them. The entire renderer had to be rewritten in DirectX. As a result, the 360 version of Marathon 2 outputs a native 720p image at 60 frames per second, rather than the 480p30 of the original. And unlike most other classic ports, it uses texture filtering, true 32-bit rendering, and every pixel of a widescreen display.

The "HD" mode of the graphics, which in other games commonly refers to a post-processing filter, is a completely new set of images. All of the nearly three thousand sprites in the game were redrawn in true 32-bit color, allowing us to put our own spin on the look of the game. Enemy sub-variants are no longer simple palette swaps, but have significant differences in their appearance. Muzzle flashes are now transparent, and the weapons have a modernized look that's still faithful to the original game. As a result, the game’s content holds up much better at 720p; the dithering visible in the 8-bit sprites is eliminated.

The heads-up display of the original game was simply huge. It consumed nearly a third of the screen vertically, and displayed many different screens of tightly packed text. This was unsuited to the Xbox 360 version in several ways, not the least of which being that when moved to a 16:9 display, there was practically no space left for the world view!

We redesigned the HUD by splitting it into several pieces, preserving the rough layout of the information it presented but revealing far more of the world behind it. The text sections were converted to icons and numbers large enough to be easily readable on a television. The improved HUD takes up far less of the screen than the original while conveying the same information.

A team with genuine love for the project. The largest problem we encountered while updating the game engine was how to preserve the feel and flow of the gameplay, but since everyone on the team was already intimately familiar with that gameplay it was easy to get a handle on issues. The change from 30 to 60 frames per second necessitated a change from 30 to 60 world ticks per second, because there was insufficient separation of updates and renders within the engine.

In most cases this was trivial to compensate for, but some areas of the game had been carefully tweaked with fudge values for the original game’s 30 fixed-point evaluations per second, and had to be re-tweaked in the new engine. Our experience helped get the game’s feel as close as possible to the original without time-consuming tweaking and test iterations.