Warnock algorithm

The Warnock algorithm is a hidden surface algorithm invented by John Warnock that is typically used in the field of computer graphics.

[1] It solves the problem of rendering a complicated image by recursive subdivision of a scene until areas are obtained that are trivial to compute.

In other words, if the scene is simple enough to compute efficiently then it is rendered; otherwise it is divided into smaller parts which are likewise tested for simplicity.

Warnock expressed his algorithm in words and pictures, rather than software code, as the core of his PhD thesis, which also described protocols for shading oblique surfaces and other features that are now the core of 3-dimensional computer graphics.

The entire thesis was only 26 pages from Introduction to Bibliography.

Polygon visibility in a given viewport: a) polygon fills the viewport, b) polygon partially and c) completely visible, d) polygon invisible.
Four steps of a viewport divisions for a simple scene