These won't split

Rhino Rhino for Windows
1

I have 2 poly surfaces and I need to split them with each other. They clearly intersect but splitting either object first fails. I need some ideas fast.

TIA RobbSplitFail.3dm (3.8 MB)

2

Hi Robert- the curve of intersection is not closed… it looks like it falls right where I bunch of surfaces come together on the more complex object. I’ll poke at it some more.

-Pascal

3

Thanks Pascal,

I’ve done a few variations on this design with success but this one seems to be what the client wants. Those v intersections at the edges are important.

Robb

4

Hi Robb - it looks like at least one surface in the polysrf is not quite split as you expect, going in. There’s one planar surface that ought to be two - you can find it by Intersect on the two objects and then CrvEnd on the resulting curve - look for the point that is generated and extract the surfaces around that point - you’ll see one of them really wants to be two.

-Pascal

5

i cleaned your split extrusion up a bit, not that it helped but it was just very messy.
also making an intersection like Pascal suggested left me with 2 curves which i could join
to split at least the extrusion.

exploding the more complex of your shapes and using the intersection curve as a split curve
let me split the object in a 5 minute job (i have an old computer) with a few problems as shown,
if you have no other solution this may help with some hand job involved but i also would suggest
rebuilding that, or at least exploding it and fixing those shown areas manually to rejoin again.

Bildschirmfoto 2016-08-30 um 02.04.12.png2404×331 16.6 KB

6

Thanks Pascal.

So I should intersect to get some curves - then inspect the objects at the ends of the curves? Reconstruct the confused surfaces… Interesting but labor intensive approach. It makes sense and I am sure that will get me out of this jam.

I exploded and SelBadObjects with nothing found. I Shrunk the surfaces then rejoined. None of that seemed to help.

Any thoughts as to how to not create such confused surfaces? I am surprised that these seem to happen so randomly. This object was created using Difference with objects Oriented along points Dividing curves. Curves & Points mirrored from 0. I was rigorous with my geometry going in…

7

Hi Robb- what I meant was that the one surface there that is highlighted in my image needs to be recreated as two - it will not split as is because it has zero-width at the bottom of the ‘v’ in the trim. Make that from two surfaces and I think things will work better.

-Pascal

8

Thanks again Pascal.

Problem is solved for now. I’m still curious as to how to prevent the creation of such a troublesome surface.

Robb