Request for Comment: Bump Maps or Normal Maps?

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Should default Celestia use bump maps or normal maps?

Bump maps
0
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Normal maps
8
100%
 
Total votes: 8

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SevenSpheres
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Request for Comment: Bump Maps or Normal Maps?

Post #1by SevenSpheres » 05.10.2021, 20:41

I'm working on updating Celestia's default data again, after about a year with not much being done in this area. (If you have mobile Celestia, you should be able to see new content shortly after it gets added to the repository.) One thing I need community input on is what kind of map should be used to display elevation: bump maps or normal maps. In either case, one type of elevation map should be consistently used.

Bump maps are used by Celestia 1.6.x, while normal maps are used by Project Echoes. Normal maps are IIRC what Celestia uses internally (bump maps are converted into normal maps before being rendered) and so are probably more efficient; but they're less "human-readable", harder to create, and they have to be png images, which are larger than jpg images and thus increase Celestia's file size.
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Post #2by john71 » 05.10.2021, 20:54

Normal maps are better. I use DXT5nm files and they are way better, than bumpmap files. Also Gimp can create normal maps from any image.

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Post #3by SevenSpheres » 05.10.2021, 21:12

john71 wrote:Also Gimp can create normal maps from any image.

I'm pretty sure that it can't properly convert bump maps into normal maps; it just assumes that the input image is not already a height map and guesses the elevation of it. There's Fridger's normal map tools, but I don't know if they're still available.

Edit: A look through the Discord server history finds this GIMP normal map plugin. I'll try it out. Edit2: I'm not sure that this is any better...

Actually it looks like I may be wrong here and the default normal map filter can convert bump maps. :think:

Okay, it turns out the problem is just that it doesn't work exactly as it should for a texture mapped to a sphere (the scale at the poles is wrong). Other than that it does correctly create normal maps from bump maps. Sorry for the confusion.
My Addons: viewtopic.php?f=23&t=19978 • Contributing to development as much as I can occasionally • Discord server admin
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Post #4by john71 » 05.10.2021, 21:22

I never used Fridger's tools, only Gimp. Normal maps are not scientific, but mainly aesthetic tools in my opinion. They have this very crisp, clean visual effect. Bump maps are lame and somehow foggy. In any case Celestia should provide a command to use DXT5nm files, because they are in almost every way superior to jpg files or bump maps.

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Post #5by SevenSpheres » 05.10.2021, 21:29

john71 wrote:Normal maps are not scientific, but mainly aesthetic tools in my opinion.

Normal maps (at least the ones that would be used in the default Celestia distribution) are scientific; they encode real planetary elevation data. See Digital elevation model.
My Addons: viewtopic.php?f=23&t=19978 • Contributing to development as much as I can occasionally • Discord server admin
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Post #6by john71 » 05.10.2021, 21:34

SevenSpheres wrote:they encode real planetary elevation data

The main problem is that in many cases you cannot see this elevation data in real life (from space), but normal maps can make or break a planet or a spaceship in Celestia. They add a special sense of reality.

Added after 14 minutes 34 seconds:
SevenSpheres wrote:A look through the Discord server history finds this GIMP normal map plugin. I'll try it out. Edit2: I'm not sure that this is any better...

Gimp 2.10 Filters->Generic->Normal map

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Post #7by John Van Vliet » 06.10.2021, 22:15

I use all Normal maps and and a copy of Fridger's tools so that the poles are correctly mapped

Gimp DOSE NOT DO THIS!!!!!!

Normal maps just work better than a 8 bit height map

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Post #8by trappistplanets » 06.10.2021, 22:48

John Van Vliet wrote:Normal maps just work better than a 8 bit height map
yeah, i agree, it reduces color banding artifacts (see https://en.wikipedia.org/wiki/Colour_banding)


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