What's the difference between Normal Maps and Surface Maps?

[ianmac]

The question above says it all really. I've searched the docs but can't find a description of the difference between these two parameters. The motherlode seperates these resources, but I can't find out what the difference is. Any help appreciated, I'm a Celestia Newbie...

[Harry]

The question above says it all really. I've searched the docs but can't find a description of the difference between these two parameters.

A surface map contains the color, just like any ordinary map (uh, I was about to write "like any normal map", which would have been a bit confusing...).

A normalmap is not a "normal" map (sic), but it contains surface normals, i.e. information about the angle of this point relative to a flat surface - it contains information about hills and mountains. This is necessary to display realistic shadows. Bumpmaps are similar, but store the information in a different way - in fact, a normalmap can be computed from a bumpmap.

Harald

[Bob Hegwood]

A normalmap is not a "normal" map (sic), but it contains surface normals, i.e. information about the angle of this point relative to a flat surface - it contains information about hills and mountains. This is necessary to display realistic shadows.

Hey THANKS for that explanation, Harry. That's the first one I've
heard that I think I actually understand.

Take care, Bob

[Evil Dr Ganymede]

But note that neither normal nor bump maps actually change the altitude of the surface. They don't actually add surface topography directly to the planetary body - for that you'd need a mesh.

[Harry]

Thanks Bob

And yes, it's only shadows, no real change to the shape of the planet. So it looks best when looked at from straight above. To modify the shape you would need (as far as I know) to use displacement mapping However Celestia doesn't (yet?) support it, and you'd need a fairly new graphics card...

Harald