The 3D Software Rendering Technology of 1998's Thief: The Dark Project

4 months ago

Thief: The Dark Project was released in 1998 by Looking Glass Studios as a purely software-rendered stealth game.
The game's rendering engine, primarily authored by the speaker, was later modified for hardware acceleration in System Shock 2 and Thief 2.
The engine was inspired by Quake but implemented portal-and-cell visibility dynamically at runtime, unlike Quake's precomputed PVS.
Thief used a breadth-first traversal of portals and cells to determine visibility, reducing overdraw with bounding octagons.
Objects and world polygons were rendered back-to-front with complex sorting to avoid occlusion issues, sometimes splitting objects across cells.
The game's CSG system used a temporal model for level construction, differing from Quake's approach, but faced issues with BSP tree splits.
Thief employed perspective texture mapping with custom routines optimized for the Pentium, supporting both power-of-two and arbitrary texture sizes.
Flexibility in rendering was achieved through a chain of post-processing functions, though some features like paletted lighting were abandoned.
The engine supported effects like colored portals and underwater fog, though some were underutilized or replaced.
Shared libraries handled vertex transformation, object rendering, and character skinning, with contributions from multiple team members.

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