as i explained in the bug #354 in the function ControlPolygonFlatEnough() there is a division by zero in case the first and last point of the bezier curve have the same Y. This patch should solve the problem for what i've seen and tested.
To see the problem is quite easy, just create a bezier curve with three points in which the first and last have the same Y: for example 0,0,0; 50,100,0; 100,0,0.
Ticket moved from /p/brlcad/bugs/355/
This patch was applied and further updates were made through r59414 and will be available in the next release of BRL-CAD after 7.24.2
Thank you for the patch! There were some very minor style issues, but you described the issue very well and the patch looked good. You were credited in our authorship file and will be announced in our release notes. If you'd like us to credit you using your real name, please provide it.