To generate this pattern the distance measure was changed to the cityblock distance and rendered in gray scale. Apart from the distance measure, the code is similar to the code of first order distance.
cd = CellDataStruct(this, 1, at, cn.CITYBLOCK);
pixels[x + y*width] = color((float)cd.F * 150);
The complete code is available here, along with most of the other examples in the gallery. To be able to run it in Processing, you'll have to download the CellNoise library from the download page.