Great one: <a href="http:&#x2F;&#x2F;www.iquilezles.org&#x2F;www&#x2F;articles&#x2F;distfunctions&#x2F;distfunctions.htm" rel="nofollow">http:&#x2F;&#x2F;www.iquilezles.org&#x2F;www&#x2F;articles&#x2F;distfunctions&#x2F;distfun...</a><p>Just go to his articles section and you&#x27;ll see a bunch more.