Leaky Boolean Operations in Rhino 4.x

[pyronaught]

Yeah, I've heard the fillet tool is still screwed up in Rhino 5 and creates the fillet as a detached edge just like it does in 4. I'd love to upgrade to 5, just have to figure out something on that student ID situation. I thought my wife was going to sign up for a college course a few months ago but she missed the deadline so I'm still waiting on that. I just can't afford the non-student edition. Although for the amount of time this leaky Boolean glitch has cost me over the last two weeks it is getting pretty expensive trying to wait it out.

[jimc]

yeah i dont blame you. 1k on a piece of software that in my case is just for home use is alot. the student version is the only choice for me also. the fillet edge thing does work but its limited in its ability. for me 75% of the time its fine but the other 25 i have to do it manually with a surface blend. in most cases you can sort of spot what its going to fail on. problem is there is no intelligence to the tool so it cant adapt to certain things and it just fails. i know some users are running the work in progress rhino 6 right now. the fillet thing has to be the most common complaint on their forum so i think they were working on that. i wouldnt expect to see that release for another year or more though.

[jsc]

My tongue in cheek suggestion is to give Fusion 360 a try. Water tight geometry every time. T-Splines for fun swoopy things. Free for enthusiasts. And I'd love to answer any modeling questions.

If you do decide to give it a try, I'll make you an offer. Send me a drawing of your part, and I will send you a file with a 3D model. The history will show how I built it up so you can follow along and figure out how to make changes.

[pyronaught]

My tongue in cheek suggestion is to give Fusion 360 a try. Water tight geometry every time. T-Splines for fun swoopy things. Free for enthusiasts. And I'd love to answer any modeling questions.

If you do decide to give it a try, I'll make you an offer. Send me a drawing of your part, and I will send you a file with a 3D model. The history will show how I built it up so you can follow along and figure out how to make changes.

Thanks for the offer, but I've got too many years invested in the Rhino learning curve to make that kind of change. Rhino is a pretty awesome modeling program really, it just has this one issue and it is probably only an issue in my way-out-of-date version.

[ednisley]

where all the triangles come together at the axis

Can you rotate those spheres by 90° to make their axes vertical? That might simplify the geometry enough to make it work or at least fail in a less awful way.

I'd use a much coarser polygonal approximation for the spheres to reduce the number of facets; more than a few dozen segments around their tummies won't make much difference in the final result.

Bonus: if you pick the number of facets to be an integral multiple of the number of slots, then align the slots Just Right, some geometric magic might happen and the whole thing will slice beautifully.

Fiddly stuff like that is probably easier in OpenSCAD, but it ought to work in Rhino, too...

[pyronaught]

The problem will happen even when there are no slots at all. I think the STL converter chooses where to put those axis points based on the geometry of the object, as I've tried to relocate them by rotating the parts before joining them and the axis points still fall in the same place. The only hack I have had some luck with is to embed a rectangular block where the axis points are in order to keep all the triangles from converging on a single point. That works sometimes, other times the leak just moves to the edge of the block. In the example above I can't use that trick because the trouble spot is in an area that needs to remain curved.

The solution turned out to be to just export only the objects required to build the finished model as a new file, then open it and merge them. For some reason that worked, and that's the kind of mystical black magic that drives me crazy.

[jsc]

Have you tried repairing the “bad” file through netfabb? It may be easier than trying to get it to generate properly.

[pyronaught]

Have you tried repairing the “bad” file through netfabb? It may be easier than trying to get it to generate properly.

No, I haven't heard of netfabb. I was kind of wondering why Rhino itself doesn't have something to repair or even identify the leaks. I usually have to use S3D to get a better look at where the problem is. I'll look into netfabb though, thanks.

[jsc]

Netfabb comes in two flavors, a program with an impenetrable interface, and a cloud service. Try the cloud service first, as it is easy to use: https://netfabb.azurewebsites.net

[jimc]

rhino has a whole load of mesh tools. rhino 5 atleast. there are a ton of tools there to repair triangles and errors.