What is the difference between the Dilate/Erode nodes Step and Distance modes? I can tell they are doing different things, but I'm interested in the technical details and the documentation does not cover it.
In Step and Distance mode, the Erode/Dilate node samples through all pixels and compares their value to the neighbouring pixels. If a neighbouring pixel has a lesser value, than it is matched the sample pixels value.
The following pseudo python shall demonstrate.
FOREACH a OF allPixels: FOREACH b NEXT TO a: IF (a > b): b = a
In Step mode, the adjacent pixels are right, top, left, bottom.
In Distance mode, the adjacent pixels include diagonal connections.
Here is a comparison of an example.