Hi Phil, well it makes things very difficult for the booleans when you have pieces that have overlapping surface areas where the parts kind of barely skim over top of each other which you have a lot of here... Intersection calculations between such things can easily have meandering intersection curves, and for the booleans to work properly the intersection curves need to define clean closed loops so it can divide things into different regions. If you take a look at the intersection curves created in your case here by selecting the 2 objects and running Construct > Curve > Isect you can see that the intersections are very complex.

Some things that I would try would be to make your simpler part to be a large filled block rather than a thin piece in order to avoid some of the skimming and if that's not successful then maybe it will be necessary to work at a surface level using Edit > Trim to cut up things rather than booleans. I'll try some of these things tomorrow to see if I can help you.

- Michael

Another thing that would help would be to replace a few surfaces to simplify them - for example if you use edit > Separate on the "side wall" pieces of the voronoi part and turn on control points for them you'll see that although it's a planar surface it's not just a simple large plane, it's made up of a lot of points that wind around. If you delete those and then replace them with simple planes (open up a planar hole and then select the part and run Construct > Planar) that might also help.

- Michael

So the trim method means to do something like get a 2D side profile curve like this and use it as a cutting object on just one piece - this will involve simpler planar projections rather than surface/surface intersections between skimming surfaces and is more likely to succeed:



That will then get it partway there, then the more difficult part is getting the other piece trimmed which will involve trying to cut it with stuff like this:



- Michael

Hi Phil, I've attached the result of a bunch of tricky trims of one piece against the other, starting with a trim of the voronoi piece against a 2D profile curve as shown above, and then extruding that 2D profile out and then the difficult trims of it as well. For the top surface I had some trim problems but since it was planar I was able to cut the edges where the crossed over each other and then build planar surfaces using Construct > Planar. This should hopefully give you enough to finish it off with a few more trims for slicing off the excess width and then joining in the rest of the surfaces to make it a finished solid. Let me know if you are still stuck with finishing it off.

Anyway, this is the main technique for difficult intersections, basically booleans are a combination of surface/surface intersections and then trimming with the pieces to discard automatically figured out by what volume they are contained inside of, followed by an automatic Join. You can kind of almost think of booleans as a sort of automated "batch mode" of trimming. For complex things where the booleans are getting confused, you can instead work with manual trimming and joining at the surface level instead.

The type of thing you had with a lot of overlapping surfaces tends to make for messy surface/surface intersections.

- Michael

Hi Michael,

Thanks a lot for your help. I will work on it tonight and try to finish it off. I originally "flowed" a flat voronoi solid ([SLD - Voronoi FLAT] against a curvy surface [SRF - Flow] to make the shape I need (in a manner similar to the Voronoi Chair tutorial). This is how I ended up with all these complex cross-connections. I don't know if I should have approached this differently...

Phil

Phil,
It's the "skimming" surfaces that Michael describes that is giving you heat.... Here's a video where I adjust some curves and cut your part.



So in the video you see me "raise the bottom curve" by a very slight amount, so it's not barely skimming through the entire bottom of the chair. The vertical curve is adjusted but you cant see it in the video. I used my "super nudge" command which moves .01mm. So I moved that vertical curve .04mm deeper into the solid to get a clean cut....

"""""""""""" I don't know if I should have approached this differently..."""""""""""""""

What you can do in the future, is model the veronoi with the base "much deeper, or thicker", then in this Boolean operation, cut the back to specs with your curve. Booleans are good to have a "complete intersection".............

Hi Phil, re:

> I don't know if I should have approached this differently...

Well, the thing Burr mentions about having pieces that punch just partway through the other rather than skimming would have helped...

Also it would usually be good to do the boolean before doing the flow instead of doing it afterwards... But in your case here it's a bit more complicated since you have 2 pieces branching off in different directions, so I'm not quite so sure.

- Michael

@BurrMan (and Michael) - Thank you so much for having taken the time to share your knowledge on these issues. The various explanations and the excellent videos really helped me to understand (a little bit) more about what I need to do to finish this model. I am very, very grateful!

All the best

-Phil