Shading not realistic - can you shed any light on this for me? (pun intended!)

Support Materials and Textures
1

Hi all, I’m creating some furniture models based on some real-life pieces of furniture. There’s a type of cabinet door where the shading just doesn’t look right when I render the model. The door is essentially a flat panel with some beading/moulding on the front of the panel. I’ve created a 3D model of the panel and beading in blender, but when I render the door in a room scene, the light/shade on the beading does not look natural/correct. The beading is brightly lit near the light source in the room (window with HDRI outside), and very dark away from the light source, with a fairly pronounced step-change between the light and dark areas. I’ve included a rendered picture that shows this (door on left of picture).
For reference, the picture also shows a door (door on right of picture) that is a flat panel with no 3D model beading, but the panel has a photo of the real-life furniture door UV mapped onto it. The light and shade on this door look correct, because the mapped image texture is a photo that was taken in real-world lighting conditions.

I’ve also included a close-up of the 3D model of the beading. Note that the shape of the beading is straight and uniform, so the light/shade on the rendered beading should also be relatively uniform, as per the real-life photo image texture.

The attached rendered image was created with only 5 samples (for speediness), but I also tried a render at 50 samples to increase the detail, but this doesn’t change the beading lighting problem.

Can anyone help me to figure out how to get the 3D model of the beading to look right?

Many thanks!

Andy_C

3D Door with odd shading, with photo texture of original door for comparison - with text, 3D Beading
3D Door with odd shading, with photo texture of original door for comparison - with text, 3D Beading2563×3016 635 KB

2

What you are looking at are problems with normal vector interpolation due to naively applying smooth shading to the entire mesh. It’s one of the most annoying things to deal with in computer graphics. There are different ways to deal with this which have different pros and cons. What you should do is make a backup of your file and then explore different solutions:

  • Bevel modifier with select edges marked as sharp and “Harden normals” setting enabled
  • Add detail loops near the corners
  • Some manual removal/adding of faces and edges
  • Flat-shade the entire mesh instead and hope for the best (this can occasionally look okay if the object is far away from the camera)
3

Hi Zyl,

Thanks for getting back to me. I’m relatively new to Blender, and I’m not familiar with any of your suggestions and don’t know where to start with each of them!
I’d really appreciate if you would give me a little more info about each…

Thanks again,

Andy_C

4

A lot of these basics are covered by the Blender manual. You should poke around: https://docs.blender.org/manual/en/3.2/modeling/meshes/structure.html#normals
Make sure you select the correct version in the bottom-left.

5

Good stuff Zyl, some interesting info there - although much of it has left me more confused!

However, I tried applying Shade Flat to the mesh as you suggested, and it had a pretty good effect - the light/shade looks much more lifelike now…

Many thanks!

Andy_C