If I shift-ctrl-select the white face and move it in z[direct edit fail.3dm|attachment], I end up with a mess.
direct edit fail.3dm (57.6 KB)
Yep. I reported this way back when. Rhino cannot direct edit something connected to a trimmed cylinder. Even one that has top and bottom untrimmed edges, but has a hole in the cylinder surface somewhere.
Which is ok with me, really, but it should not allow it or something. Otherwise, I mess something up and don’t realize it for 2 hours and then I’m sad.
Well basically my approach to this solid editing stuff is not to use it on anything that is not composed of entirely of planar surfaces - with a little caution this can be extended to some non-planar untrimmed surfaces with all linear edges. And check the result after every operation. That’s it.
Me too - makes it much less useful than it could be.
Hyup…
In the end, this actually looks like just a bad programming mistake - like a transformation that got made to the world coordinate system and then not transformed back to the object or something. Otherwise, why would all the objects behave like the following?
All the bad rows of control points go to almost the same place, regardless of where the object is located in space… 
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That fixes the super-crazy results. But when I try it out, I see another problem. When I move the bottom edge of a cylinder with a hole in it, it seems to work fine on the first move but if I move it again, the surface of the cylinder gets weird. Do you see that? Sorry my video doesn’t show the side view where I do the trimming, but you should be able to reproduce from this I hope.
Hi Peter -
Personally, I think you are expecting way too much from direct editing in Rhino.
When you put your display mode to Wireframe you see right a way what is happening:
Even though the first edit no longer creates a totally out-of-whack surface, the result is not something that I would use for any down-stream operations.
I’ll ask a developer if this can be tuned up for this case - but I guess that, if it is at all fixable, it will only apply to a narrow sub-set of all thinkable geometry.
For flat surfaces, direct editing is fine, yes. But always check your wireframe after doing this.
-wim
I totally get that. Maybe direct editing should not be an option on non-planar objects in Rhino? I don’t know.
Hi Peter,
As Wim said, that might be fixable but it would only apply to simple extrusions, when it is deformed into something that can still be represented as an extrusion (i.e. moving whole edges in the direction of extrusion).
The bigger point is that editing twice the same surface is always going to be problematic – direct edit tools can only complexify surfaces (or keep them at the same complexity), so there is almost no hope that you would be able to get back to the original solid after multiple edits. Checking the surface structure before and after direct edits is a must or you will quickly end up with very high CV counts.
Still, I don’t think direct editing should be restricted to planar surfaces only, it’s useful in other cases.
I’ve logged an issue: https://mcneel.myjetbrains.com/youtrack/issue/RH-62308