What is going on here??

jeff hammond

hmm. I'm not so sure about that.

Click on the very first link in this thread. The conversation has picked up over there.
I just posted a picture showing what happens if the curve is no longer recognized as an arc

[edit]. Oh, I should add that while the wiggling of the rotate tool might be a glitch, the same shape can be arrived at by rotating to ~180 deg.
This shape isn't happening due to that weird pump action of the rotate tool.

Wo3Dan

@gilles said:

The strange whith this is that it only works whith shapes based on arc or circle, .......

I've got it to work with curves as well.
See attached file.
I started with an arc. Exploded it. Applied the smoove tool get the first deformation to be sure there wasn't an arc left. Welded it into one curve. P/P the enclosed face several times with P/P+Ctrl.
Divided the edges underneath through their midpoints.
Selected these lines (blue in model).
Applied the rotate tool in green direction as shown in model.
This is just on example out of thousands what you can achieve.
Notice that curves remain (scaled) curves just as circles do.

Wo3Dan

Smooth_curve_deformation.skp

Jim57

It beats me why this works. Best I can see, it's a glitch in SU. It works from trying to rotate a line in a direction that it can't rotate in, and the result is a deformation in a different plane than the one the Rotate tool is calling.

It took me a while to notice that the trick is to bind the Rotate tool (second click) normal to the line being rotated. Jeff Hammond's last example shows the line itself being rotated, instead the normal (perpendicular) getting rotated.

Interesting!

JIm

putnik

Jeff, I'm unable to open the original Qglitch.zip on Windows..

jeff hammond

@putnik said:

Jeff, I'm unable to open the original Qglitch.zip on Windows..

hmm.. same here.. i can't open it either and i've since trashed the file thinking 'i have it online if i ever need it' i should check my links better.. i've been having trouble uploading to sketchucation lately hence me uploading to my .mac account..

it's just a skp of the jpg posted right below it...
here's another version of it that's basically the same thing iirc
glitch.skp

putnik

Thanks Jeff. I too would like to know why after wiggling the Rotate tool the geometry doesn't return to its original half-cylinder shape when returning to 0 degrees deformation with the Rotate tool still active. Manipulating any other type of geometry does that.

Pilou, I don't think you quite understand Jeff's question. You are explaining why convex shape is created, but that's not what Jeff is asking.