Boolean Union Problem

In the attached file I have three pairs of surfaces. The one on the right is the original pair. I would like to offsetsrf by 3/8" inward and join to form a closed polysrf. But it will not join.

If I split the original gray polysrf using the end frame of the original red surface, I can join up as shown in the center or left. It appears that all joints are tangent.

I have highlighted the intersections—which are all different. If I intersect the end cross section used to create the red at the right with the gray at the right I get a line along the full length. If I intersect the resulting sweep2 or networksrf, I get the partial line shown.

So I am looking for ways to approach this.

Problem (511.8 KB)

split the surfaces by isoparm at the location of your choosing, then use matchsrf to get them lined up, then join.

this is not a boolean job… this is a split and trim job.

1 Like

Problem (372.4 KB)

After split and trim I have the inside and the outside. Is there some simply way to close this?

Or do I need to break down and do the inside and outside as two distinct sets of curves so that I can ensure the edges are coplanar?

there are 3 parts in this file… what do you want to do with each part?

closing them you can use the cap command or intersect a surface and trim/join

It needs a figure-8 top and bottom, essentially the red capped and trimmed by the purples. The problem is that during offsets, they surface edges are no longer planar. The starting curves are all coplanar at the top and bottom.

ok, cap the red surfaces then take the purple surface and extend it on all 4 sides so it extends outside the red object then boolean split.

Hello - extend the surfaces and then cip them with a plane.


Hi @miano,

You get the short line because the red surface passes slightly through the grey one at that point and forms an intersection within your tolerance setting, whereas the end of the red section does not unless you relax the tolerance slightly.

I’m not clear which surface or surfaces you want to offset, nor in which direction(s). Could you sketch over the image to show what you want?

In the meantime, your surfaces are quite complex - you will find intersects and offsets are better if you can start from simpler surfaces, which in turn come from simpler curves. You should be able to remake your shape something like this:

Note that to get three surfaces to join at a common edge you will need to use the NonmanifoldMerge command - you cannot use Join here.


NonManifoldMerge will produce a non-manifold polysurface. However it may not be very useful and in some cases cause problems. For instance OffsetSrf a non-manifold polysurface will result in several polysurfaces. Trying to create a solid with OffsetSrf on a non-manifold polysurface will fail to create the solid.

Good point David. And, in any event, if @miano’s intention is what I now suspect it is, the OffsetSrf outcomes will need some surface extension/intersection/match work to get planar caps because the initial surfaces are not perpendicular to the caps.

I broke down and drew the frames for the inside surfaces to match the outside surfaces posted above. Here’s what I was trying to get.