I'm not sure where to post this, but this seemed like a good place.
Steve Culver posted a link on the ABS forum to a freeware program that allows you to create the end grain of a billet and see what the pattern will look like with twisting (variable tightness) and grinding (variable depth). It comes preloaded with a few standard end grains. I downloaded it and it does what it purports to do (at least with the preloaded patterns). I have not tried to create any diagrams to upload to it yet, but Steve has and says it works well for predicting pattern development using only twisting and grinding. It also has something called "burn-off" which as I understand it, simulates a user-chosen percentage of loss due to forge scale.
Steve's post with instructions/description is found here: http://www.americanbladesmith.com/ipboard/index.php?/topic/2765-thor-ii-software-download/
The link to the freeware is here: https://www.stahlundseide.de/html/thor_ii.html