What is a "world space normal" map?

Hi, I have bought Substance Painter some weeks ago and I did a bit of pratice with.
I have tried to use the maps (Gloss/Spec) in Blender, with not nice results but whatever…

When I do the “bake”, in Substance, I obtain a “world space normal” map. (It has more colors than the usual normal maps and I guess to have made it in Blender too for once by error by pressing on Bake…)
And I want to understand what is it, what is its usage and how to use it in Blender, and why should I use it.

Thanks

Full disclosure, I’ve never used any of these before, but here’s my understanding.
“World space” is in contrast to “tangent space” which a normal map would usually use. A tangent space normal map will be mostly blue, because blue corresponds to the “facing out” vector in tangent space. A world space normal map will have all sorts of colors, because blue just means “up” in world space. The advantage of a world-space normal map is it does not require additional per-pixel transforms, so it works faster. The disadvantage is it won’t work right if your object changes shape (character animations). You should be able to use a world-space map in local space, which will apply the object orientation.

Oh many thanks! So it exists just because of better performances during rendering? No other advantages?

http://wiki.polycount.com/wiki/Normal_Map_Technical_Details says:

Normal maps can be made in either of two basic flavors: tangent-space or object-space. World-space is basically the same as object-space, except it requires the model to remain in its original orientation, neither rotating nor deforming, so it’s almost never used.

If you’re generating one from a higher-poly model, world and object space maps are not dependent on the shape of the low poly. They’re simply a dump of the normals from the high-poly. Tangent space maps use the low-poly as a reference. This allows them to support deformation, but means the normals are just the “difference” between the high and low poly. So tangent maps need to be re-baked if the low-poly silhouette changes.

Btw, when exporting from Substance Painter to Blender, export metallic/roughness maps, and use them with the principled BSDF node that was added in 2.79.

Thanks, I have 2.77 but I wanted to learn how to implement the maps manually before using those node. :slight_smile:
Just to know well what I am doing!
But, why to export in metallic/roughness? Isn’t Blender using the glossiness/specular setting?