What's the easiest way to fill a non-planar region?



I’ve tried playing with Sandbox and also reading other discussions but nothing is doing what I need so far. I’m going to be very specific.

I have 4 points. Two of them lie at ground level, and the other 2 lie a little above ground level, both at the same altitude. The two points on top lie almost right above the 2 at ground level, but not quite. One is a little on one side, the other is a little on the other. That means these 4 points don’t lie in a plane, and if I put lines around them, Sketchup cannot fill the almost-rectangle because it wouldn’t be a flat surface.

I want it to get filled with a smooth surface that twists slightly. Ideally I would like this to happen in such a way that horizontal cross-sections of the surface are all straight lines, going continuously from the straightly line between the bottom pair to the straight line between the top pair.

My way of doing this has been to fill in the region between my points with triangles, color them, then hide all the edges. This gives an approximation of the surface I want, but is a little off, and is tedious to make.

Might anyone suggest a faster and/or more precise way of making the twisted surface that I want?


Check this plugin: Curviloft .


Yeah that does just what I asked, thank you!


Actually, after trying to actually use it on something, I find the program crashes or freezes almost every time I run a function from the extension.


Can you share an example SketchUp file that you have problem with?


If there are just 4 points you can easily draw a diagonal manually.


Multiple horizontal straight cross sections are needed.

@j0equ1nn, draw a vertical rectangle.
Divide it into n parts by (n-1) horizontal edges accross.
Select one vertical side, (n-1) edges and rotate it q degrees, using the base edge as axis of rotation and the base vertex as rotation point.
Repeat this process on the other side, though in opposite rotation direction.

p.s. the ‘Eraser’ tool, while holding down [Ctrl], lets you smooth the edges within the “rectangle”.


This solution wouldn’t work for what I’m doing. My process starts by importing a list of points. These points need to be connected in a precise way and it’s important that their coordinates do not change. Even if that weren’t the issue, this idea just takes way too long because I’d have to do it something like 150 times.

I appreciate everyone’s help on this forum but I’m probably not going to continue using Sketchup. The bottom line is that it’s not designed for what I’m doing, and there are other programs that are. I’m making models of abstract mathematical models, not for architecture or woodworking or urban planning or other things the program is good for.


Okay. This is the file after I finished more or less what I needed. I did use the plugin you recommended, but had to use it separately on each pair of lines (and most of the lines used are now hidden in the figure, to create the desired effect).

This may or may not be enlightening as to why the plugin didn’t work better, but it will at least give you an idea of the weird kind of stuff I’m making.

d=7 faces.skp (227.4 KB)


Allright, i don’t know which parts of your model you created intentionally since it’s kind of an artsy object. But here is what i did:

d=7 faces_edited.skp (293.2 KB)

As for the Curviloft usage, i suggest you to spend more time on reading documentation, watching some video tutorials online. You need to give some proper edges for curviloft to calculate in order to achieve best result.
In this case outer edges of each colored surface would be suitable to make Curviloft create the face:


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