There are wrong lines after objects intersection.
For example, when a sphere intersects a surface, the line of the circle is broken.
Please post an example file… --Mitch
A Rhino file, not an image please, it’s impossible to tell from your image what the problem is… --Mitch
your object is in relation to the working space far too small. if you increase the size of this micro planet by for example x20 the intersection works. this is not ideal in general and i would recommend resizing the object or using a smaller working space.
I don’t think so… The sphere has a radius of about 30mm for a tolerance of .001, the intersection should work. However, the object is pretty far from the origin and that, with the fact that the intersection falls directly on the sphere seam line may be causing this. (plus the surface is a block, but that shouldn’t matter in this case).
If you move the object closer to the origin, the intersection is correct; if you move the plane just off the seam, even far from the origin the intersection works as well. so I think it is the combination of the two that is causing some floating-point fuzz in the V5 intersector in this case.
In the V6 WIP, it works correctly without doing anything, so I think this “bug” has been fixed.
–Mitch
If you rotate the sphere so that the edge is not coplanar with the plane, the intersection will work. In Rhino 6, intersecting works without having to rotate.
actually true when you measure it, it seems the grid has been adjusted that it looks small, but having the intersection working after increasing the size is usually a good sign that the object was out of tolerance… but in that case not the problem.
yes about 5 meters not much but too much in that case that centering actually makes it happen again.
Yes, he has 400 grid lines at 100mm spacing… that makes the grid extents 40 meters… 
oh my… 40 meter in mm… sounds like a lot of work 
i wonder why that happens at all. its not that far away to be honest in relation …
by the way @uit exploding the instance, rebuilding the surface just a little denser 3 points instead of 2 in both directions makes it happen either.
You can make the grid extents as large or small as you want, it’s only visual, it doesn’t affect modeling as far as I know…
–Mitch