Normal Maps for Dummies?

Cenobite451

So, yeah. Feckin' normal maps, how do THEY work? Seriously - I haven't got a clue. Bump and displacement maps I can wrap my head around; the fact that they're in simple greyscale helps. Normals, though... I checked out the Wikipedia entry, but it's basically Greek to me. Can anyone provide (or point me in the direction of) an explanation in comparatively basic English - the kind of language a lit major might understand?

Ta for any help. :red:

Richard Haseltine

A "normal" is a line sticking out at right angles for a surface, and that tells the render engine which way a bit of a surface is facing and so how much light it should catch. A normal map overrides the real normals - it uses the three colours that make up each pixel (red, blue and green) as values for a new normal, and the render engine lights that bit of the surface as if it was facing in the direction set by the map and not its real direction - which fakes detailed surface relief.

Cenobite451

Thanks; that's fairly helpful. So what sort of circumstances would be give a strong advantage to normal maps versus simple bump mapping? (In other words, why bother?)

Szark

Normal maps don't displace the mesh like Displacement maps which in effect Normal maps are simliair to Bump maps but they give a better illussion that the mesh is displaced than bump maps and takes a fraction of the memory needed which is great for Games.

PS and great for low powered computers or props in a scene that are in between close to the camera and distant, a midway position if you like..

SpottedKitty

The main difference is that a bump map only "pushes" the surface outwards in the direction of each polygon's normal. A normal map can "push" the surface outwards in whatever direction is encoded into the RGB colours of each pixel of the map image. That's why the normal maps always look sorta bluey-purpley with greenish and reddish shadows, what you're seeing is the amount and direction of "push" swivelling a little bit this way and that.

Although, to be honest, I've never been sure I've ever actually seen the effect of a normal map — apart from my collection of Genesis characters, I have a few props (not all from DAZ) that came with normal maps, and applying them in the proper slots in the Surfaces tab never seemed to make any visible difference. (I know one scenery set I had to return because it just plain couldn't be made to work right in D|S had normal maps that were gibberish even in Poser, how common that might be I can only guess.)

SickleYield

Normal maps are awesome in a game engine, but it's hard to get either Poser or DS to handle them in a way that works well. It's why you'll find most artists using the combo of bump + displacement instead. It's not a difficulty issue. For me, at least, generally I have to actually create a normal map in Blender to make the displacement map FROM.

SpottedKitty

I'm a lot more comfortable (and a lot more confident!) using bump+displacement myself, at least when something goes worng I can usually see it and fix it.

Do you mean you can create a displacement map from a normal map using Blender? Or is some other program needed as well? Maybe I can finally get some of those are-they-or-aren't-they-working props finally fixed up so they'll kink in all the right places... :roll:

SickleYield

I do a hires sculpt in blender. Then I bake a normal map from that. Then I use decompose on that map in the Gimp to make a disp map.

SpottedKitty

Intriguing — how does this "decompose" work? I have used up to Photoshop CS3 at work, but I've never needed anything better than an ancient copy of PSP at home. Maybe I can get some of those dodgy normal maps converted into something I can at least tell if it's going to work.