Sorry for the vague title. I don’t know the name of this situation, but in almost all my renders I get these waves that look like shadows (though a flat surface). Here is an example:
You’ll notice the fanning-clamshell type shadows around the edge of the circle. I know it is barely noticeable, but usually it’s more noticeable, and not scaled down. Any idea how to fix that?
If they are usually better visibly and not scaled down, it would be a good idea to put a picture with that online…
I guess you mean the (very slight) shadows that look like they are coming from a center and go to the edge? I think these are sub surface artifacts because your surface consists of triangles in that area.
That’s it exactly. Subsurfed and triangles. No work around the artifacts?
Here’s a larger pic. However from what you are saying, these shadows are not caused by any subsurfing, because it is simply the default cube. ( Click here for full a closeup of these waves.)
small
If I am correct it is an entirely different effect in your second pic.
Subsurf problem: Easy, don’t use triangles when working with subsurfing. You can use “degenerated” triangles where two points are at the same position, so it looks like a triangle but is a quad. Example. Imagine a mesh circle. If you want to fill it, you can extrude it and scale the extrusion to zero. If you now remove the doubles, you have a set of triangles around the center. This will be ugly when subsurfing. When you just don’t remove doubles, the geometry looks the same but consists of quads and works with subsurf.
Problem two: Don’t know exactly, looks like a low color resolution. Don’t know how to avoid it yet. I noticed it too, but for my usage it always was negliable (only seen when zooming extremly, not visible with structured textures, not visible with AO).
Thanks Inamre, you’ve been great help. Never thought of scaling to “0” and not removing doubles. Can’t wait to try both suggestions you have there. Cya.
*edit: Oops, forgot to ask, what is AO?
*edit: Nevermind, Ambient Occlusion. Got it. Nifty 
Your second picture is gradient banding. Try increasing your antialiasing to 16 (set OSA to 16 in the render panel.)
You can also fix gradient banding in post process by taking your image into photoshop, duplicating the layer, adding about 1% noise until you see the banding vanish. Then lower that opacity level of that layer to the lowest setting that still hides the banding (probably about 80%) and flatten the image. You lose the banding but the trade off is that you add grain.
You really need to watch out for banding if you are using a two color blend for a background world material. Sometimes it helps to mix it with a few percent of some irregular pattern applied as a texture.
Lynda
AO is ambient occlusion. It will not help you by smoothing the gradient. It is a kind of indirect ligthing method which itself adds a little noise, so the gradient is not that visible. Found in Material settings -> World settings.
