Hi. I've recently begun a relationship with Rhino as a hobbyist and most of the time it is very gratifying. It does happen sometimes, though, that I get violently frustrated with some quirk of the software.

I find solids a bit hard to manage, and one thing that's especially killing me is the unwanted edges that appear in the middle of solids when extruding or joining:

1. Make a solid cylinder

2. Extrude the top surface

3. You now see that the side is sort of split into two by a new edge

Or alternatively:

2. Make another solid cylinder exactly like the first one but with half the height. They should be placed on the same spot.

3. Do a boolean join of the two cylinders

4. Again, there's an edge, even though their sides were completely flush

How do I remove those edges??

Three cheers for the person who can help me out - the relationship is suffering.

P.S. Also having a hard time controlling the zoom feature in perspective view. Sometimes, after having moved around a lot, it's like it has reached maximum zoom even though I'm still far from the object I want to observe...

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Something like "simplify solid" or "clean up solid" would be super. Or to be able to simply select the edit points of the solid and delete them. Not possible?

Booleans are just a shortcut for splitting and joining. There is a command for unifying flat surfaces that are on the same plane, MergeAllFaces, there's no such tool for other shapes, so the booleans aren't going to do it.

It's just not generally a good idea to do things like make a cylinder longer by extruding one end and booleaning, that sort of thing is not what they're for. If you want to modify simple solids try the solid edit tools (in the menu Solid->Solid Edit tools)that let you do things like pick faces and move them, or turn on "solid points" that you can edit to make simple changes.

Thank you for the answer. I see - that makes sense. Then, say I have a pipe that I want to close off in one end with a disc with a certain thickness, or, say I want to join together the ends of two pipes with the same girth, but don't want there to be an edge - how would you go about doing that?

Hi Kristian- can you post examples of these? It is not clear how things are arranged in your two scenarios.





Try doing boolean unions of each these three pairs of tubes. They are completely flush, and so one would expect there to be no edges left except for the - well - actual edges.

How would you go about making nice, simple solids out of each of the pairs?

Have the tubes perhaps been created in a wrong way? I really hope I'm expressing myself clearly :)

Hi Kristian- I see- no, Rhino will not merge these objects at the surface level. The thing to keep in mind is that Rhino objects do not know what they are- in general they are just surfaces or collections of surfaces, and there is no provision for understanding that a surface is in fact part of a tube with certain characteristics identical to another tube and can be merged. The exception is for planar surfaces- MergeFace or MergeAllFaces will merge coplanar faces in situations similar to this, but this is not extended to cylinders. It could be, in theory, for cylinders, but it is much more difficult for the general case- freeform surfaces.



I can see how this could be a bit challenging, mathematically - I guess the pibe shape is quite specific, as cases go. Thanks for the answers - I'm learning :)

One way this might be achieved, though, is if one could simply select the offending edit points and delete them, recalculating the surface between the proper end points. I can move the edit points of the redundant edge around, but there's no way it will let me delete them - this is what frustrated me the most, I guess.

Well, the two surfaces involved are completely separate and do not share any points- the way surfaces work is rather different from meshes, if that is your point of reference...



Oh, right! Yes, that is definitely what's tricking me. Thanks again.

I'm learning really fast, which has to be a testimony to the usability of Rhino. I believe I can now give a better answer to my own question about joining together two pipes or cylinders end to end and having their outer surfaces become one.

I now know that "solid" is just an alias for closed polysurfaces. That means I can explode it and delete one of the two surfaces that I want to make one. I can then extend the other until it meets the surface which the first was connected to (e.g. the end cap).

If the end surface is not planar, I can extend it beyond the end and then use trim to cut away the part sticking out. After these operations I can join together all the exploded surfaces, creating a solid once again.

Solving these little problems with the tools and constraints given is like a fun game - so rewarding! :)



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