Hey guys,
As a test, I’m trying to normal map a mail box and I’m getting a really odd-looking bake; I figured posting the bake and the corresponding render might be enough to spot the problem (I’m sure it’s fairly basic), but if not, I can post the blend or more images. Thanks.
You have set smooth on, which is interpolating the normal values, causing that gradient effect over flat areas on your normal map. Either turn off set smooth, or turn on auto smooth. I’d also recalculate normals, and check for doubles just to be safe, because I see what appears to be duplicate faces in some places.
When baking I always set the low poly to smooth. I do this with pretty complex models actually without any problems. For me baking is usually a process of experimenting with the depth / bias settings, fattening the high poly (alt + s), shrinking the low poly (alt + S) etc. Of course, after the baking is done I shrinken / fatten them back to their original size 
As a test, I’m trying to normal map a mail box and I’m getting a really odd-looking bake; I figured posting the bake and the corresponding render might be enough to spot the problem (I’m sure it’s fairly basic), but if not, I can post the blend or more images. Thanks.
It looks like you need to temporarily scale down the low poly before baking. And indeed check for double vertices (remove doubles) and inverted normals (recalculate normals outside).
The brownish colors in your normal map does not look good. Looks like overlapping or inverted normals.
Normal maps have the greatest trouble with 90 degree edges - I’m not sure why, and they work fine when raytracing, but game engines just make a mess out of it. Adding a small bevel to these edges will solve that and result in a much prettier end result.
Secondly, you’ve got some mirrored parts, and the problem is that both sides are trying to bake, but with different results. Select all copied parts, go the UV editor and press G and type in the texture width (so, G, 1024, for example), so that these UV are moved to the 1-2 UV space instead of 0-1. Now they’ll be textured as usual, because textures tile, but the baking only happens in the 0-1 space, so only the ‘original’ parts left will be used in the bake.
Here’s a good page on normal mapping issues/technicalities/techniques.
Zwebbie: I have a mirror modifier applied, so I’m pretty sure I’m only getting one side of the mesh without duplicates.
That’s some great info, guys, I appreciate. I’m still running into trouble, though. I added some extra edges to the cylinder forming the round silhouette of the mail box and it seems the wavy lines are improved, but only slightly. (For now, I removed the mailbox door so that explains it being gone from the map and render.) I imagine there must be a much easier process than the one I’m using, and I obviously don’t know it. A couple problems I continually see are circled in the images, such as what look like points in the base mesh that are nowhere to be seen on the model and something causing sharp lines.
I think the mirroring is the cause of those sharp lines - the solution’s even easier now, though, just turn off the enable modifier during rendering button in the Mirror panel.
That seems to have helped quite a bit, thanks. I’m still a little bothered that I’ll probably be having to edit the wavy lines out in Photoshop; is that a pretty typical practice, or what?
