I have a metal drum mesh, and when I bake its normal map, I get the weird colors (see attached pic). I'm talking about the horizontal gradient shift of color. There's no deformation like that on my mesh, how come the colors are like that? I've tried various spaces (camera, world, etc) but it's still bad (though the horizonal gradient changes with each one). Also tangent space returns a blocky blue color all over.
Can someone please tell me how to get a good normal map out of my mesh?
Solved, thank you very much Luke B. There's still the question of scaling one of the two overlapping versions a bit (the low res one for example) in order to get really good results, but that's how it's supposed to be done.
=== UPDATE 2
After further following the advices of Luke B, I've used multiresolution modifier on my low-res mesh, and baked from there. It looks much better than before, the color artifacting are down to a minimum, really, with some corrections in GIMP it's quite usable: