I just updated to Rhino 8 SR9 last night and I am seeing an anomaly with Boolean Difference that I have never seen before this last update. I was creating a simple cup with holes in the bottom. Using cylinders and Boolean Difference to create a simple cup with holes in the bottom. Very primitive stuff. I saved it to and STL file for my 3D printer. But in my slicer this cup had a strange arrow shaped surface plane next to it. I imported the STL file into Rhino and saw same thing. In working on this I found that it matters how many holes I make in bottom of the cup. As well as the holes orientation. I am posting this just to let someone know.
Original file:
Boolean Difference Problem.3dm (1.0 MB)
Starting with this sample. I can test a variety examples:
I made examples of cups with 1, 2, 3 and 4 holes in the bottom using Boolean Difference. Here you see the original objects on left and the STL objects on the right and the anomalous surfaces circled.
Then in making these samples I found another problem. If I make this cup with three holes in the bottom at the 3, 7 and 11 o’clock position. What I get looks correct. However, if I make the three holes in the 12, 4 and 8 o’clock position. It appears to remove the whole bottom of my cup. Yet, if I look at that cup from underneath it or turn it over. I see the bottom is there…