Understanding Normal Map's

ruudvangerven

Hello everyone,

The last few days I've been trying to figure out a normal map "issue" but have no luck with it and hoping someone can clarify what's going on.

I've used 3D Coat to sculpt, retopo and bake a stylized Bonzai tree. 



Everything seems to be fine untill i watch / preview the normal map itself (setting it in the diffuse channel or checking the normal map with sketchfab material editor.

Just like the diffuse, i expect the normal map to be a "smooth image" wrapping around the tree. Instead of this the Normal Map clearly shows the uv islands / seams and this drives me a bit crazy because how can they work like this? 



My colleagues are used to Zbrush and when i watch their normal maps or for example this random example on sketchfab:

This is how  the normal map is supposed to look, right?? 

Also i found this image during my search:


My model looks like cube 4 - 5 while instead of 2 - 3.

Any thoughts / work-around for this?

Thanks!

Grtz,

Ruud

m4dcow

So you are seeing those discontinuities when you preview the normal map in your diffuse because your UV shells are split in those places and each side of the shell may not be oriented the same way. This is why you can't rotate shells in photoshop arbitrarily and have them work as expected. So you could actually have 2 shells that look the way your normal map does at the seam (different), but work perfectly well.

I would suggest that you try to do a bit better job on the UVing of your asset (some texture stretching is acceptable to avoid that many seams). Also show the normal map applied as a normal on the model, because it might be easier to tell what the problem is if any.

ActionDawg

Normal map "seams" at the edges of islands are totally common and expected. It's not really a seam per-se. Just how tangent space normals work. If it renders fine, it probably is fine.

The image of cubes you posted is essentially only relevant when not using a synced tangent basis (other than showing that you cant have split normals but not split the UV islands. Take a look at the wiki here and the Marmoset Toolbag baking tutorial for a walkthrough on proper technique (it applies to any program).

Eric Chadwick

Yep, good advice above.

This image might help too
http://wiki.polycount.com/wiki/Texture_Baking#Tangent_Basis

ruudvangerven

Thank you guys for the fast reply and clarifying the subject, much appreciated!!