Taking a bite out of a corner with gumball...?

Really easy scenario I need help with: I’m trying to understand all the limits and constraints of gumball and the push/pull editing of solid orthogonal shapes.

If I draw a simple box in Sketchup, then I draw a line on the front face from top to bottom, I can then push that corner of the box back (on axis with side faces) To take a rectangular “bite” out of the box’s form…

When I create a box in rhino, then extract and divide the front face into two as I did before in sketchup, then join all the faces together, I should be able to push the corner back on this like front face as I did before… however, rhino doesn’t trim the top, bottom and side surfaces like sketchup does… it creates a hole where the corner is pushed back, but those other faces remain in their original position

I know the right thing would be to boolean difference more effectively, but I’m trying to work out how to do this with Gumball if at all possible… is this a limitation of gumball or am i doing something incorrectly?

You can split faces and push them around with the gumball - or just dragging even - but unfortunately, Rhino is not fully capable of adding in surfaces where there were none before - so you either get a hole or it drags the surrounding edges with it.

What you CAN do with a single split face is use ExtrudeSrf with Solid=Yes and DeleteInput=Yes, or Extrude with the Gumball using the Ctrl key and it will produce the desired effect - sorta. It’s fairly limited, so right now the best is usually to use the classic Boolean ops. Let me see if I can do a quick video…


This might help with general Gumball questions…

but in answer to your specific question, your extrusion back into the box will only work as you expect if the hole is not on an edge. In the edge case, the side wall surfaces are not trimmed.

Yep, that’s what my video illustrates… The difference between my first Gumball drag and the second one is that I pressed the Ctrl key after starting to drag to extrude instead of just drag. I also dislike gumball extrusion because the key combination and timing for a precise distance is so unwieldy.


Awesome, Appreciate it guys… Im trying to get more people in my office online with Rhino… they’ve been in Sketchupland for a while, and these kinds of gumball moves seem to be the most intuitive for them…

Again, Thanks!

You know how to do this but just don’t like it right? @mikko has been working on making the GB easier… maybe start a new thread with suggestions if you have some. I’m in the camp of “works fine here already” for what it currently does which are linear edits. I would above all want curvature continuity maintained when editing polysrfs but that doesn’t seem possible or would be a huge project.

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Hi Chris, you can try this macro, probably can be scripted but do not know how.
First pick the surface while pressing Control-shift and then run this:
! _CPlane _Object _Pause
_Rectangle _Pause _Pause
_Splitface _Pause _Curves
_SelLast _Enter
_SelPrev _Delete
_ExtrudeSrf _Pause _Pause
_SelLast _MergeAllFaces

There are already a bunch of manipulator threads floating around, the main problem is there are just too few modifier keys, so it’s painful when you have to press/hold a certain combination and try to type in a distance constraint. Extrude is the worst, if you hit Ctrl too early, you move the Gumball location instead of extruding.


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one of the weirder things when coming to rhino from sketchup is that rhino doesn’t auto-merge everything.

in sketchup, if you draw a line across another line, the lines will split and the intersection will be a single vertex… in rhino, it’s still two different lines and you have to explicitly tell it to split them.

in rhino, it’s as if everything you draw in sketchup is drawn as a group and if you want everything to melt together, you have to explode the objects (via different commands than you’d use in sketchup to do this)…

once you get used to it, you’ll probably find rhino to be better in these regards… you can draw directly on top of other objects without things sticking together… however, if your typical workflow in sketchup is mostly push/pull based, you’ll probably still prefer sketchup since it’s faster / less steps.