« on: October 21, 2014, 08:57:36 AM »
The Optimize Orientation button tries to find an orientation of the model that will minimize the *volume* that requires support. (ur current version over-estimates the volume somewhat, which complicates things further).
For the bunny model, depending on your overhang settings, the minimal-support-volume orientation is not necessary the orientation where the flat base is on the bottom, because the *volume* underneath the ears goes all the way to the ground plane (and hence is quite large). You can see this by running the Orientation tool under analysis. The default settings (Support Vol Weight=100) are similar to the Optimize Orientation button in the print view. You should see a set of arrows in the scene, with little bar-graphs beside them. The green bar shows the support volume measurement, and it is smallest when the bunny's nose is on the ground. The flat-base on the ground is another one of the arrow options, and you can see that the green bar is slightly taller.
The orientation optimization doesn't know about "printability", and it doesn't know about our meshmixer support-structures (the branching trees). That would be too slow to compute in the optimization. So the volume measurement is a heuristic that lets us do something reasonable, quickly. However there are cases where it is not as useful, and large-flat-base objects are one of those cases.
However for those objects you can easily put the flat base on the ground yourself =)