The attached 3dm file has a full sphere in wireframe - that looks like an arc because isocurves are turned off and it has not yet been display meshed.
Do not shade any views, run the following scriptlet:
import rhinoscriptsyntax as rs msg="Select object for bounding box" obj=rs.GetObject(msg,4+8+16+32,preselect=True) bb=rs.BoundingBox(obj) rs.AddBox(bb)
You will see that the bounding box is wrong (should correspond to the box you see on the locked layer in the file). It is the bounding box of the visible seam of the sphere, not of the full sphere.
If you shade the object, even if you then switch back to wireframe, the BB is correct. So it works as long as the object has a display mesh. The normal Rhino BoundingBox command must also force meshing, as you see the object display mesh details show up in Properties>Details even if it had none before.
Known bug? Didn’t see it on youtrack. Seems pretty odd that this has never been seen before though…
WrongBB.3dm (41.4 KB)