Rounded skylight - surprisingly difficult

Hi all! So, I need to create a skylight. Actually, I need to reproduce the ones in the middle of this photo, to be specific. Now, the rectangular base is easy; a few extrusions and you’re done. The tricky part is the smoothly curved window itself. I didn’t think it’d be any trouble; I stupidly assumed I’d just extrude a rectangle up a bunch of times, then use proportional editing and scaling to get that nice cross-section. What I forgot was that this leaves clearly visible corners all up and down the object, no matter whether or not Set Smooth is turned on.

My next attempts involved the Boolean intersection of a squashed sphere and a cube. That produced ugly meshes, especially after I flattened the edges so they’d fit correctly within the frame. I also tried manually cutting out the points from a sphere, but that yielded equally poor results. SubSurfing methods proved futile as well.

The real issue here is that the form itself must have no visible corners or edges whatsoever, yet its bottom must terminate in a rectangular shape. It’s proving quite difficult, and I was just hoping one of you expert modelers could give me a hand. This is a relatively insignificant part of the model I’m working on, but I’m becoming very interested…er, obsessed with figuring out how to do this. It’d be nice to get it to work.

Thanks so much in advance! =D

Ok I modeled a rudimentary version of the shape you are after.
win.blend (47.9 KB)
Use it as an idea how to go about getting the final shape.

here’s what to do, 1 - add a grid 2 - select the middle vertex of the grid 3 - turn on proportional edit mode with the O key - 4 move the vertex up using the mouse wheel to adjust the influence - 5 when you have a nice mound shape, leave edit mode, and use the scaling widget to scal it slightly in one direction - 6 go back into edit mode, toggle off proportional edit mode with the O key if you haven’t already, then select one half of the vertexes and slide them over a bit using the grabbing widget. here’s an illustraion.

Attachments


I´d suggest you use NURBS.
make a profile, a follow path, generate the surface, tweak a bit and convert to mesh.

Modron, I cannot believe I didn’t think of that. Thank you so much for the help! I’ll definitely go with that route.

I also appreciate your help, musk and arexma. The problem with the subsurf technique is that I can’t get the rectangular shape, though, and with NURBS…well, maybe it’d work, but I think that’d be unnecessarily difficult. Maybe.

Anyway, thank you very much, all!

Subsurf. Piece of cake.



The trick to working with subsurf is to use extra edge loops to stabilize the shape. Here I’ve used four edges to get a nice flat, rectangular outline to the skylight shape, although three will do.


A couple more loop cuts across the plane in both direction (also shown in the first image), then select the central face and move it up a bit in z, then extrude the whole thing to give it a bit of thickness.


Here’s the render.


Here’s a more extreme version. In this one, I had to increase the subsurf render level to 3, to avoid some flat spots in the outline toward the top of the bulge. Adding a couple more loop cuts across the middle of the original plane would also have done the trick. Even in the extreme case, the extra edges stabilize the shape – looks like it just popped out of a vacuum mold.

Bah, I tried stabilizing my subsurfed version with extra loops before, but I’m realizing now why it didn’t work. Another obvious method! I feel like such a noob. =D Thanks again for the help, everybody!