Blender Underground

I'm trying to extrude some windows in a smooth hull with subsurfing, and I keep betting distortions in the material around the edges that look like dark smudges. I've seen these in some models I download but they don't eem to show up in the renders. I've tried adjusting the normals and all that.

Is there some material or texture settins that keeps them from showing up in a full render even if they show up on the mesh in the 3d windows and renders with basic materials?

Can you post a pic of the problem?
It sounds like multiple verts but a pic would make it clear, it may be something different as I think you know about removing doubles.

I used edge crease at 1 and it's on a subsurfed mesh. I extruded inward and got the ugly blotches I see here. I've seen these on some models that are textured and materialed and render great without it showing up. I wonder if some texture or such covers these.

You can see them on the edges of the hull outside the extrusion.

In many cases I fix these by using a loop cut to slide an edge up to the edge of the extrusion, at about .9 closeness. If I do it here it dfistorets the shape of the hull and gives it sharp edges and points on what I want to be a damn smooth, curved hull.

Did you crease the extruded part? that might fix it.

yes, i extruded the crease, it came out creased.

Is the shading set to "flat" rather than "smooth"? (it only shows in Edit mode).

I found the problem, Prof. too few verts and faces. If you take a simple single square and extrude then move it with a subsurf, you get a lot of that fold over from the sufsurfed skin bleeding into the edges. If you have a lot of faces and extrude something made of multiple faces, it works better. Also with a lot of faces you don't get as much distortion in the whole shape when you need to so an edge loop to tighten one up.