DevLoft Questions

Happy New Year everybody!

Like many boatbuilders I am keen on developable surfaces. Rhino 6 offers the new DevLoft command, however only as an “international” command (_DevLoft) and there is no description of it in the German language help file.

  1. When using the hyphen version (_-DevLoft) in Rhino6 SR 21 I only get three command line options, the Untwist option is missing. Has it been removed (according to the english help pages it should be there…)?

  2. When using _-DevLoft on two curves the initially proposed surface makes sense and remains so after accepting it (pictured at the top). However, after changing the density or adding a ruling line out of the command-line, the generated surface reverts to something that looks rather like a straight ruling loft - not really developable (pictured at bottom):

Any suggestions?

Thanks, Konrad

I’m using SRC Rhino 6 SR22 2019-12-17 and the untwist option is present.
DevLoft Snip

I’m seeing the same behavior when changing the density.

I also get a different surface if I add a ruling line even when the ruling line exactly matches an isocurve of the initial result.

Example file for anyone who wants to try it themselves: DevLoftEx001DC.3dm (101.5 KB)

Hello - I see that - Untwist sorts it out… after that I could not get it to do the weird thing again, even in another run of the command… still poking…


@pascal You didn’t reproduce the problem. It occurs on completion of the command so Untwist does not sort it out and it is repeatable. This needs to be fixed. It is a fundamentally flaw and will corrupt a users work if they don’t recognize it when it happens…

How to reproduce it using this example file. DevLoftEx002DC.3dm (80.7 KB)


Select the two curves. DO NOT press enter or right click. Note the appearance of the ruling lines. They are correct.

Type d to change the density. Type a different number than the current value. Right click to change the value. Do not press enter or right click a second time. Note the appearance of the ruling lines. They are still correct.

Press enter or right click to enter and complete the command. Note that the ruling lines fundamentally change and are now very different and fundamentally incorrect.

Screen captures below illustrate the steps described above.

Hi David - on changing the density, here, the screen does not update to the new density (bug) and still looks ‘correct’ at the old density. If I force a redraw by moving the view, I see the density is correct, and the ruling is not (bug). If I click Untwist, the ruling and the density sorts itself out and Enter gets me what I believe is the right surface - do you not see that?


I see the same.

I see the same.

I see the same The user should not have to click Untwist to force the ruling lines to be updated after the density is changed. That is a but in the software.

I see that you have submitted two YT’s for the bugs. These should be a priority to fix since they cause fundamentally bad results.