Game Engine Black Book: Wolfenstein 3D by Fabien Sanglard

Author:Fabien Sanglard [Sanglard, Fabien]
Language: eng
Format: azw3
Published: 2017-10-06T04:00:00+00:00

This part of the code relies heavily on unit circle principles. As we need to know how much to go vertically when advancing on the X axis and how much to go horizontally when advancing on the Y axis, the tan function is especially useful. This is easier to understand with the unit circle drawn (circle radius r is equal to 1).

Figure 4.44: Unit circle.

When advancing 1 on the X axis, the ray moves up tan(θ) on the Y axis. The reciprocal is calculated as follows: move 1 on Y axis, move tan(90 − θ) on X axis. To accelerate cos, sin and tan calculations, the engine uses lookup table. See 4.11.1 "Cos/Sin Table Lookup".

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