The Rotating Planets in the Classic Game: Elite

This paper examines the graphical techniques used to generate rotating 3D planets in the classic 1984 space simulation game, Elite. Specifically, it describes the algorithms and geometric principles used, focusing on the drawing of planetary craters, meridians and equators. Emphasis is placed on the fast circle, ellipse and line-drawing algorithms, and on the game's orthographic projections that are used to display the elliptical features on the planet surfaces. We also describe the way the game rotates 3D objects at sufficient speed, by avoiding floating-point multiplications. The analysis was made by manually reverse engineering the game's 6502 assembler code. The findings contribute to an understanding of the programming tricks necessary to make early 3D video games viable, and illustrate how minimalist mathematical models can achieve compelling visual realism, all while running on a 2MHz 8-bit home computer.