While testing something for another thread -
I created a terrain mesh “solid” by extruding it with the gumball. Then I wanted to sub-object select the bottom of the mesh and SetPt it to Z0. In my custom UI the selection worked instantly. I wanted to make some screenshots using the default UI, when I tried it there on the same file, Rhino hung trying to sub-object select the bottom faces. I couldn’t figure out why…
…until I saw that in the default UI, I had AutoCPlane on and set to Object. And in my custom setup AutoCPlane was deactivated. So I then tried it with just a relatively dense mesh box and AutoCplane set to on and object. Same thing - except the mesh box was simpler than my terrain file so after about one minute, the selection did appear.
Obviously it’s trying to figure out an autoCPlane for many, many individual faces… But maybe there should be some sort of short-circuit exit from the calculation for these types of situations.
Here is the mesh box I used.
100x100x10 mesh box.3dm (525.3 KB)
Try turning AutoCPlane On>To Object and ctrl+shift selecting the bottom face…