Some algorithsm work by creating a first corse-graiend or approximate result, and then gradually creatting more detail. This can be especially useful in image processing. For example Marr's primal sketch using Laplacian-of-Gaussian filter to initially look for objects and intereting parts of an image at low resolution, and then focuses mroedetiled processing on the araes of interest.
Defined on page 258
Used on Chap. 12: page 258