Blender Render : square shadows on smoothed model with bump textures


I’ve often encountered this problem.
A drawing is worth a thousand words, so…

This is Blender Render, not Cycles.

Left : the model - flat shading
middle : the model - smooth shading
right : the model - smooth shading and default material + cloud texture ( only influence is normal)

Middle has a smooth transition between lit areas and shadows.
Right shows the geometry underneath. Is there a way to avoid that ? A workaround or a real fix ?
Thanks !

I’ve no idea if it happens in Cycles.

It is related to the light type. Are you using an Area lamp? If so try a Sun lamp or Spot lamp. This is not an issue in Cycles.

Could you post an orthographic render of the same picture ? The perspective view makes us view your sphere at different orientations between the three views.

I think it is because normal maps modifies the shading but not the topology of the meshes, you should get the same silhouette for the three spheres in orthographic view. You’ll have to subdivide more if you want it gone.

EDIT: I did the test, see by yourself

Left: flat shading
Middle : smooth shading
Right : cloud texture as normal on smooth shading

upper line: no subdivision
lower line: 1x subdivide modifier


Thanks !

Ok, it’s a geometry problem. I had some hopes there were means to get a good looking result without adding faces (which is one of the reason to use bump maps after all) but apparently it’s not possible.

I’ve looked better at the results and actually the middle result (with the smooth shading) looks nice but is completely wrong. It suffers from not enough faces too.

It’s easy to spot on the follwing test. The second range is Gimped, I’ve added the middle shadows on left and right results and it’s obvious it’s wrong. The shadow area is much too big and looks weird especially on the right result.

(orthographic view, sun lamp, Blender Render)

So, no easy trick, just more geometry is the solution !

Cycles will show smoothing artifacts at some angles.

Eg, a smooth UV Sphere backlit by a Sun lamp (rotation X:-66°, Y:0, Z:0):

And a camera positioned close to the ‘grey line’ showing an undesired effect on the large flat polys, which disappear as subsurf is increased:

Good to know for Cycles. Thanks !