The graphics and physics code increased the game's system requirements, and the team worked to optimize performance during development. They struggled to improve the game's memory usage: the process consumed nearly as much time as the creation of the physics model, according to Church. Programmer Eric Twietmeyer ran weekly tests of the game's performance by disabling certain parts of the code—such as the physics calculations—to isolate which parts used the most memory. By 1994, Blackley's physics code took up only 1% of CPU time, with the rest allocated to the terrain renderer. Blackley optimized his code by converting the mathematical calculations of air from the 3D game world into a "math-friendly space", during which time the Navier-Stokes equations are applied. Afterwards, the data is returned to 3D space. According to "Computer Gaming World", this method increased speed by "a factor of 100, with almost no loss in precision." The team had trouble with complex memory-related glitches during development. Church called them "crazy", and programmer Greg Travis noted that debugging the terrain cache system was a "nightmare".