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I have a mesh which is a "rough cut" of a final shape that is to be 3D-printed and I now want to curve the mesh into the final shape but am having trouble understanding how the deforming tools work.

The shape needs to be curved in two directions, see the red lines in the images below:

enter image description here enter image description here

...so that the final shape looks like this (from the front and the side respectively):

enter image description here

It's important that only the top of the object deforms; the bottom has to mate with the thing below it and so must not change. How best to go about this? Answers may begin with the usual "don't start from here" :-).

To complete the picture, here is the back of the shape to show that it is a shell:

enter image description here

Rob
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  • If you just need to roughly deform it, you could try to use deforming tools like a Lattice modifier, otherwise if you need another exact shape, you could either reshape it manually or, maybe, using a reference exact shape and then "projecting" your current shape onto the reference, maybe even shrinkwrap could help. – m.ardito Sep 12 '18 at 21:59
  • Lattice looks useful but I have to subdivide the shape for it to be effective so I think maybe I should start again with a smoother top-half to the shape. What I really want to do is add bezier edges between vertices. – Rob Sep 12 '18 at 23:08
  • Do you need to loft a particular set of curves, or just eyeball the result? – Robin Betts Sep 15 '18 at 13:15

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If you need to loft a specific set of curves, Bsurfaces is a very good option: it can be used for modelling as well as retopology.

But for this job, probably:

  • Duplicate ShiftD the front edge of your box.
  • Rotate it up, and use it to form the back profile, and remove doubles at the corners. (Blue, below) .There are many ways of getting the shape here - the Loop Tools Add-on > Space, Proportional Editing, Vertex Smoothing are all handy.
  • Select all but one or two of the corner vertices, and extrudeEY,EZ the edges a bit. The sections to be bridged must have the same number of vertices for a clean result.
  • After selecting the new inner edges, CtrlE Edge Menu > 'Bridge Edge Loops'
  • In the tool's settings, adjust the number of cuts, and the smoothness, to suit.
  • Cut the result in half, and assign a Mirror modifier to manually fill the holes, make other tweaks, perhaps using the tools already mentioned.

The approach in this answer is sub-division modeling, in which you keep the hand-made topology as simple as possible (not necessarily regular,) and let Catmull-Clark sub-d do all the work of creating smooth curvatures. With relatively few vertices, you can manually adjust the number to be equal in the horizontal and vertical profiles to be bridged.

  • Ctrl-select the path between two symmetrical vertices in one profile - you will see the number selected at the top of your 3D view. Select the corresponding segment in the other profile, and note the difference.
  • Add vertices by subdividing edges, or remove by dissolving, to make the numbers equal. Don't worry about where..
  • ..because you now use the invaluable Loop Tools > Space feature to spread the vertices evenly along your chosen segments. If it's a lot of work, you may do this work under a Mirror modifier, to halve it.

You will probably want to match segments with high curvature in separate batches from straighter ones, to maintain sufficient density in those areas.

enter image description here

You could forget the extrusion step, and just bridge the original edges, but I don't think the curve is quite as good.

You can assign your Subdivision Modifier after this, with the rest of your model, so they match.

Robin Betts
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  • Thanks, I'm slowly learning the value in Blender of sticking with regular shapes. I've followed your procedure but the trouble I had on my first attempt with it is that the shapes of the front and back of this thing do need to be different and so I've ended up with a different number of vertices on each. Bridging works but it bulges on the sides, which I guess is down to that. I don' suppose there's a "make number of vertices the same" tool is there...? Otherwise I'll just do it manually. – Rob Sep 18 '18 at 08:54
  • With relatively few vertices and simple shapes, I would normally copy one profile to the other, and then tweak the curvature without changing the number of vertices .. but see the edit to the answer. The bulging on the sides is probably due to a 'Profile' influence in the Bridge Edges tool .. reduce or eliminate that setting. – Robin Betts Sep 18 '18 at 09:29
  • That's excellent, very close now, no bulge when I have equal numbers of points. My final problem is that, after making my solidified shape, when I add a sub-division surface modifier I end up with artefacts on the inner, running across it from side to side, a bit like a cat's cradle. I was going to try doing it the other way around (perform sub-division before solidifying) but the solidifying process generally produces a few shards and, if it's working on a sub-divided object, I end up with an awful lot of shards to find and remove. Anyway, I will ask separately about that. Thanks a lot! – Rob Sep 18 '18 at 20:34
  • Ah, got it, solidify doesn't cope well with ngons, use Face Fill instead of just Make Face to remove the complex faces and the cat's cradle goes away. Sorted. Thank you so much! – Rob Sep 18 '18 at 21:06