How do I bake a correct normal from a hollow sphere?

JSlade

So, I've made a hollow sphere in 3DS Max and cannot get a good bake on the inside portion of the mesh. 

Here is the UV layout:

Here is the resulting normal map from xNormal:
I've made sure there are no overlapping/inverted polygons on the UV shells at all, and I still have no idea how to fix the artifacting issue.

Bartalon

If you're talking about the funky colors in your normal map, most of that looks to be pixel padding, which is a good thing.  What's it look like actually applied to your mesh?

Additionally, a cage would fix any projection issues you're having, if you are actually still having issues.
http://wiki.polycount.com/wiki/Texture_Baking#Cages
[edit] I'd also recommend baking to a 2:1 texture map to optimize your UV space (like a 2048x1024 for example)

JSlade

The black mesh is the cage, and here is what the result looks like:

Bartalon

Oh, my mistake   That's definitely strange.  Are the edges around each hole chamfered at all?  Is each UV island set to its own smoothing group?  I also wonder if the inconsistency of your UV islands might have something to do with it.  There appears to be a good amount of distortion throughout: oval shapes for what should be circular holes, and very little actual UV space for the polygons representing the thickness of your sphere

JSlade

1)Yes, they are slightly chamfered.
2)No. I was going to add additional smoothing groups but grew very tired of working on the mesh at the time.
3)Yeah, I'm not sure how to fix the distortion. I placed seams inside of each circle, selected the outside polygons and used spherical projection to isolate the outside and then did the same for the inside. What you see is the result, and I'm not sure how to fix the distortion without manually doing it.

Edit: I used the "relax until flat" function and got a slightly better layout. Not sure how much it will help

Scruples

UV's from the same geometry? if so then this should fix most of the issues since as you had a lot of uv's with zero map area.
A box type unwrap with more seams might be better for this as you still have a lot of stretching.

JSlade

Scruples said:

UV's from the same geometry? if so then this should fix most of the issues since as you had a lot of uv's with zero map area.
A box type unwrap with more seams might be better for this as you still have a lot of stretching.

I'm not quite sure what you mean by that first bit. 

huffer

You had basically one pixel or less on UV/texture on the portions that mattered - the inner rings, so there was not enough information for a good bake. I suggest keeping all inner rings on a separate smoothing group, and on separate UV shells, you could arrange them as a long horizontal strip. This way there'll be enough space for them to get enough bake info.