When to and when not to. Normal Maps.

I’m a newbie just trying to learn the basics of blender to transfer meshes to ue4.

The question is in the title, should I always create normal maps for my meshes.

It can depend on how high poly you really need to go and what kind of surfaces.

If your surfaces are jagged stones or crumbling walls or cobblestone floors then you should pretty much always use normal maps. Or even for light wear and tear on mechanical bits. But sometimes if you are modelling something that is with clean surfaces and you have a decent poly budget, you don’t really need a unique normal map and can instead rely on tiling normal map for small surface details. In fact for the recent BulletTrain demo, for the interior of the train there were no unique normal maps since the shapes were relatively clean (seat cushions, rails etc), but the characters/weapons did use normal maps since they get so close and also since it would have taken way too many polys to get that level of detail for what the geometry did. For example, even if we had the poly budget to model out all the crazy straps and buckles for a character, it would probably alias like hell from a distance since its too noisy, or the details would not pop at all from a distance since the LOD wouldn’t have any normal for them. A nicely normal mapped material in that case can both look better and be more performant. So a normal mapped mesh can be a bit more forgiving of aggressive LODs in certain situations. Of course you can always go all-out and bake a custom normalmap for each LOD but I don’t see that done often as it is time and memory consuming.

It takes time to figure out when its appropriate. I suggest you try both approaches on some simple assets to get a feel for the tradeoffs. Ie, you can add a few more polys and get nice bevels right into some meshes and skip custom normalmaps.