Extreme difficulty w/boolean difference


boolean mcneel help.3dm (8.4 MB)

attached you’ll find a model in which I’m trying to subtract from. i have tried repositioning
the pieces, increasing tolerances and modifying the cutters (light grey) to try and make a "clean’ connection. however none of these have helped. any suggestions?

(Pascal Golay) #2

Hi Foot - please indicate what is being cut and what the cutter is - you have a number of objects piled on top of one another, some surfaces, some meshes - I have no idea what you’re trying to do.


(David Cockey) #3

@pascal He said the light grey objects are the cutters. I didn’t find any meshes but a bunch of polysurfaces which look like they started/imported as meshes and were converted to NURBS surfaces using MeshToNURBS. It looks like a general mess.

(Pascal Golay) #4

Yeah, you’re right- too hasty . Thanks. But yeah, it is a mess.

@Footy_Ball so far, BooleanDifference seems to work on these objects.


(David Cockey) #5

@pascal BooleanDifference works if I select a few dark gray polysurfaces to subtract from. It fails if I try selecting all the dark gray polysurfaces in one group to subtract from.

My thought is the jumble of polysurfaces needs to be cleaned up first before trying to any more diagnosis. Ideally the geometry would be rebuilt with much simpler, degree 3 polysurfaces.


thanks for your reply, any ideas about how to clean up or rebuild the dark grey models?

(Brian James) #7

I’d remodel the dark grey objects to save time given the number of tiny patches and overlaps present. Here’s an example using End Osnaps to draw polylines and interpolated curves using the existing objects as a guide. I then constructed the surfaces shown using the Sweep2 command which requires two rail curves for each surface and any number of cross sections. Only the top surface used three though. The last step was to use Join to join the surfaces into a closed solid.
Sweep2_setup.3dm (288.2 KB)


I discovered that the angle between object and cutting object must be not close to 0


thanks for the replies, brian thanks for the help. I’ve tried that method on the other light grey model but i cant seem to be able to do it. any suggestions with what I’m doing wrong with the other piece?

(Brian James) #10

Post a model of what you’ve done and I can take a look.


I’m having a lot of trouble with doing the outline like you described any sort of help would be great outline sweep 2.3dm (3.7 MB)

(Brian James) #12

That’s not bad, the one thing to make sure of is that your End Osnaps are enabled and you place the end points of each new line or curve when the End indicator shows up. Most of your intersections are good but some are not and these will yield surfaces that don’t meet up and hence won’t join.