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I have a plane to which I've added a subdivision modifier and a solidify modifier. All looks good if it's flat-shaded but it seems to curve towards the center if I set smooth shading:

bulging plane

I guess this is to do with normals (I'm a complete beginner when it comes to this aspect of things)?

The edges between the sides and the top and bottom are hard and sharp (which I want - I don't want a curved bevel-like effect).

But I want the top surface to remain looking flat until I start doing something with the displacement of the vertices of the faces introduced by the subdivision modifier.

This issue came up as I wanted to apply a noise texture to the surface - if I don't use the solidify modifier then I can get the effect I want (which requires smooth shading so that one doesn't see the hard edges between the faces introduced by the subdivision modifier). But then adding the solidify modifier means I get this odd curving effect towards the edges.

If I turn off smooth shading then I don't get this odd curving effect but then I start seeing the edges between the subdivision faces which I don't want either.

Noise and shade smooth.
noise and shade smooth

Noise and shade flat.
noise and shade flat

Any suggestions would be much appreciated.

Here's my .blend file

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  • $\begingroup$ If I apply the solidify modifier and then mark the edges as sharp this seems to achieve the effect I want. But are their alternatives? Do I have to apply the solidify modifier? $\endgroup$
    – George Hawkins
    Feb 6, 2022 at 12:59
  • $\begingroup$ Did you crease the edges under Solidify Modifier>Edge Data? It helps if you could post the .blend file. $\endgroup$
    – eezacque
    Feb 6, 2022 at 13:27
  • $\begingroup$ I tried creasing. I did include my .blend file - it's linked at the end of the question. Thank you for taking a look. $\endgroup$
    – George Hawkins
    Feb 6, 2022 at 14:06

1 Answer 1

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This is a consequence of Smooth Shading, which smoothens out all corners, instead of just those you have in mind. You're not the first one to stumble across this, and you'll not be the last one. See, for instance here

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  • $\begingroup$ Thanks for pointing me in the right direction. $\endgroup$
    – George Hawkins
    Feb 6, 2022 at 15:42

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