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I am new to blender and wondering what is the most common approach used to model curved surfaces. I created this simple object (A bed).

simple bed in blender

I am trying to change the top surface (shown on the left) to a concave (arch like) shape (shown on the right) enter image description here

I tried sub dividing and smothing the edges but with no success. Any suggestions on how I might achieve this?

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I made a video demonstrating one of the ways to go about doing it. As Lukasz mentioned you COULD use Bezier curves but it all depends on what you're wanting to do really. Demonstration of making headboard.

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  • $\begingroup$ Thank you, the video was very interesting. It took me a while to figure it out, but I learned a ton of stuff in the process. Much appreciated. $\endgroup$ – Johnos Mar 14 at 8:52
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I was able to do it in surprisingly few steps using a shrinkwrap modifier.

Here's my version of your starting shape.

enter image description here

I noticed that yours isn't at the worldspace origin. You will want it there for the steps below. Select your headboard in Object Mode, right click on it, select Set Origin, and then choose Geometry, to make sure you're object center is in the middle of your mesh. Then press Shift + c to force the 3D Cursor to the worldspace origin (just in case it isn't there already). This will reorient your view, though that outcome was not intended. Press numpad period to get recentered on your selected object, if necessary. Then press Shift + s to bring up the Snapping menu, and choose Selection to Cursor. Now your object is centered at the Worldspace origin.

Start by creating a mesh cylinder (Add > Mesh > Cylinder) and take note of the starting options I chose in the Operator panel to the bottom left of the 3D View. You may find that you can't use the same numbers because of a difference in scale between my version of your headboard and your own. I chose 48 because that allowed 12 sides of the cylinder to be placed precisely between the two points of intersection shown in the pic below, at the two red arrows, which is what you want. 12 is the magic number, based on your very own model, because that's the number of sides that designates the row of faces that you want to build into an arch.

enter image description here

Here's what it may look like after you have the new shape in place. Don't worry about how it looks or how long the cylinder is. It doesn't matter.

enter image description here

Next, make sure you're in Object Mode, select the new cylinder you just made, and hide it (h), then select the headboard, and go into Edit Mode. Select all of the vertices shown below. These are the ones you want to change into a new shape. Next you will want to create a vertex group, which will remember this particular selection of vertices, and allow you to target it later in other operations. Create the vertex group by clicking the "+" icon under the Vertex Group Section of the Object Data tab in the Properties Panel. With your vertices selected, press Assign.

enter image description here

Next, go back into Object Mode and, with your headboard selected, go to the Modifiers tab of the Properties Panel and create a Shrinkwrap modifier. Assign the vertex group you created to it. You may also want to unhide your cylinder again (Alt + h in Object Mode) so that you can find it more easily in the next step.

enter image description here

And finally, assign the target, which is the cylinder you created earlier. This will appear to have no effect until you hide the cylinder afterwards. If you want to make this effect permanent, you will need to apply (Ctrl + a) the shrinkwrap modifier. After doing that, you can delete your cylinder. You don't need it anymore.

Hope this helps.

enter image description here

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  • $\begingroup$ Very nice due to movement outside Z axis. $\endgroup$ – Markus von Broady Mar 13 at 16:04
  • $\begingroup$ Thank you @R-800, this looks promising. I did not quite get what you showed, but I can see the curved shape and I think it's just a matter of making sure my parameters match up. Very helpful, much appreciated. $\endgroup$ – Johnos Mar 14 at 8:29
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You can select the part to be curved, set Transform Pivot Point to Active:

Press S to scale, Z to scale along Z axis, 0 [zero] to completely flatten along that axis towards the active (white, selected last) vertex. Then you can press CTRL + I to invert selection, H to hide those vertices, select the middle of that part, enable Proportional Editing with appropriate falloff (here I've chosen Sphere):

Use your mouse wheel to adjust the influence range to be as big as possible without moving the edge vertices (you can hold Shift for more precision), accept with left click and press ALT + H to unhide all geometry.

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  • $\begingroup$ Thank you, that looks like a solution also. $\endgroup$ – Johnos Mar 14 at 17:16
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The shipped add-on Loop Tools comes with a 'Curve' operator. It will fit all vertices in a loop to selected vertices in that loop, using a cubic or linear interpolation (here,cubic):

enter image description here

  • (On the left,) the original shape
  • Adjust the central vertices to the desired height of the curve, select all the vertices in the loops you want to remain fixed. Leave others unselected.
  • Invoke Loop Tools > Curve
  • (On the right,) the result.

You can restrict the interpolation to Object X,Y, and/or Z.

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  • $\begingroup$ Thank you Robin, I tried the Loop tools on Blender 2.91.10, but cannot get the shape you show. It makes an attempt, but nothing approaching the curve shown. I will spend some more time with the loop tool and can see the circle option working nicely, but the curve is proving difficult to control. $\endgroup$ – Johnos Mar 14 at 8:33
  • $\begingroup$ I did find the tool a bit counter-intuitive to begin with.. it only works on true edge-loops.. miss a vertex, and it will try to include it in the curve between the selected ones. Have a play on simple subdivided planes. You can't exactly define the resulting curve. It fits a spline to selected points. I'm more of a sub-d modeller, maybe this is of limited use. $\endgroup$ – Robin Betts Mar 14 at 9:42
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It's best to model the top part with Bezier curves, setting the left and rightmost vertices (marked red) to Vector. Then extruding the curve, converting it to mesh and modeling the remainig part.
enter image description here.
Extruded Bezier converted to mesh should be something like below.

enter image description here

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  • $\begingroup$ Thank you, I had tried initially with bezier curves, but thought there may have been a more straightforward transformation from an approximate shape to a curve. I will watch a few tutorials on modelling with bezier curves. $\endgroup$ – Johnos Mar 14 at 8:55
  • $\begingroup$ It takes a while to model Bezier curves to shape, but the result is always as desired. Should you need faster curve modeling, learn also NURBS curves. $\endgroup$ – Lukasz-40sth Mar 14 at 9:39

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