Can I add verts to a model after baking a normal map?
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I've baked out a normal map for a model doing the high to low res deal. I noticed a couple areas where I wanted to insert a couple verts to fix the silhouette. Once the verts are added that area now shades all shitty and you can see the triangles as the light passes over it. Is this not allowed, must I go back and rebake it after I have tweaked the low res mesh a bit?
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Some times you can get away with this, say if you have a simple cylinder type object with hard edges on both end caps, then the normal isnt doing a whole lot to compensate for the smoothing, and you can add/remove verts without much issue. Generally this is a really bad thing to do tho.
With object space maps you can edit the geometry to your heart's content, adding and removing geo as you please because it overrides the vertex normals. Not that its helpful to you, just a fun bit of info.
[edit] One more thing to note:
When you're adding/removing verts/edges on your lowpoly, you will not only affect the smoothing, but you will effect the ray direction of your cage/bake mesh, so if you have to regenerate normals, you may need to regenerate AO, any automated textures like detail passes from crazybump etc, depending on if any details come out any more/less skewed after your changes.
But if you want to be really hacky, you could lock all your vertex normals before doing the extra geometry cuts, then manually edit the vertex normals of the vertices you added to match the original geometry. That way you don't have to re-bake at all and you shouldn't have any visible artifacts.
It is a bit of a pain to do this though, I would only recommend it as a last resort (eg. if you've already finished your textures completely and don't want to have to deal with re-baking everything), and I'd only do it for minor edits, since it'll be a huge time sink if you do a lot of geometry editing.