subtracting brep/geometry components

new to all this.

I do not want the 'roof' of the big blob to continue through the smaller blob that is sitting on top of it. does anyone know how I can do this? these blobs are assigned to geometry or brep components.

thanks for any advice.

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Replies to This Discussion

Permalink Reply by David Rutten on October 11, 2009 at 8:24pm

Hi Dahu,

you have 2 intersecting Breps (from Rhino) and you want to move the upper one until it no longer intersect the lower one?

--
David Rutten
david@mcneel.com
Seattle, WA

Permalink Reply by Anthony Dahu Mumagi on October 12, 2009 at 9:22am

Hi David,

I have tried using boolean difference in rhino on a sphere and a cube, this works, fine.

But when I try using it on these shapes it does not work. Is it because they are open ended tubes?

Permalink Reply by Danny Boyes on October 12, 2009 at 4:14am

I think I understand what you're after. If you don't mind the two BReps being joined then a simple Boolean union will remove the intersecting portions of the surfaces, otherwise a boolean difference will keep them as separate BReps but the big blob will have an impression of the smaller one in it's surface. Solid Boolean components are found on the intersection tab.

Permalink Reply by Anthony Dahu Mumagi on October 12, 2009 at 6:44am

Thanks,

I made these blobs by lofting some curves. So are they surfaces or solids? I think surfaces right?

I want to be able to move them around but have a rule so that if one blob is going through another blob one of the has to have its surface cut, in this case I want the big blobs surface to be cut as it forms the roof of a large space and the small blobs floor I want to continue.

Eventually I want lots of blobs which I can move around freeely knowing that they will stick to the rules.

The boolean difference answer looks good but doesn't seem to be working. Could that be because they are surfaces and not solids?

Thanks.

Permalink Reply by David Rutten on October 12, 2009 at 11:52am

For a proper Boolean operation you cannot have naked edges be part of the intersection. If your shapes are open (poly) surfaces, it still might work, as long as the inersection curves all happen on the internal faces and internal edges of the shapes.

Another problem which frequently occurs with boolean operations on open objects is that the normal direction of open objects is undefined. Sometimes they are 'inside-out' which inverts the boolean operation.

--
David Rutten
david@mcneel.com
Seattle, WA

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