I'm working on updating Saturn and its moons for default Celestia, and I need normal maps for several moons. I at least need a normal map for Iapetus, since Project Echoes uses a model and I'd prefer not to use models for near-spherical objects by default. It would also be nice to have better normal maps for Enceladus, Tethys, Dione, and Rhea than the ones in Project Echoes. (Mimas is irregular enough to use a model by default, and Titan doesn't have good height data.) To do this, I need to convert existing bump maps to normal maps.
Unfortunately, most tools for creating normal maps don't work correctly for a texture mapped to a sphere (the scale near the poles is wrong). The only tool I know of that does work correctly in this regard is Fridger's NmTools; however it doesn't work correctly with bitmap source images, such as PNG images. I keep getting results like this:
So how can I convert a bitmap bump map to a normal map that maps to a sphere? There must be some way, given that Celestia Origin and Project Echoes exclusively use normal maps, at least some of which must have been converted from bitmap images. I guess I could just not be so perfectionist and use a model/bump map/incorrectly scaled normal map for Iapetus and possibly other moons - or even an already existing Iapetus normal map, if there is one - but knowing how to do this would be useful in general.
Also, on the topic of Saturn's moons, here's a surface texture for Titan using the alpha channel as a specular map, just like Celestia's Earth texture. Credit to FarGetaNik and Askaniy for the source textures used.
Added after 45 minutes 32 seconds:
Edit: The Iapetus model/heightmap (as well as Enceladus and Rhea heightmaps) is derived from here, which has no clear license, so unless the license is clarified and compatible with the GPL it can't be used in default Celestia. It seems that default Iapetus will have to remain without height data for now. I'd still like an answer to my question though.
How to make normal maps that map to a sphere from bitmap images?
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Topic authorSevenSpheres
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How to make normal maps that map to a sphere from bitmap images?
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- John Van Vliet
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Topic authorSevenSpheres
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John Van Vliet wrote:Fridger's tools require that the input image be a 16 bit SIGNED integer RAW!!! image
that is to have pixel values from -32768 to +32768 and in a raw format
Yes, I know. I'm asking how to create normal maps when this is not the case. As I said, it must be possible since it's apparently been done.
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- trappistplanets
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there are citations you can useSevenSpheres wrote:Edit: The Iapetus model/heightmap (as well as Enceladus and Rhea heightmaps) is derived from here, which has no clear license, so unless the license is clarified and compatible with the GPL it can't be used in default Celestia. It seems that default Iapetus will have to remain without height data for now. I'd still like an answer to my question though.
Code: Select all
To cite these results, the required citations are:
Schenk, P. (2010) Global Topographic Mapping Of Saturn's Midsize Icy Satellites: System-wide Thermal And Impact Effects, Amer. Astron. Soc., D.P.S. meeting 42, abstr. 9.16.
Schenk, P. (2010) New Moons – First Global Topographic Maps of (Saturn's) Icy Moons,
http://stereomoons.blogspot.com/2010/11/new-moons.html.
you can just use those as your "credits" when you implent them into default celestia
There is a limit to how far we can travel into the stars.
Owner of "The Grand Voyage" addon series
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Owner of "The Grand Voyage" addon series
Collaborating with Dangerous_safety for the still developing Cer system
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Topic authorSevenSpheres
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trappistplanets wrote:you can just use those as your "credits" when you [implement] them into default celestia
Thanks, but that's not enough. Celestia is licensed under the GPL, which allows the program to be used for any purpose, even commercially. Content included by default must be compatible with that license. If there is no stated license, it's assumed to be incompatible.
My Addons: viewtopic.php?f=23&t=19978 • Discord server admin
Celestia versions: 1.5.1, 1.6.1, 1.6.2, 1.7.0, and some unofficial versions like Celestia-ED
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what was the original DEM you used to make iapetus,looks like it has coverage sckenk's map alone doen't have?John Van Vliet wrote:the normal maps for those that want to use them
There is a limit to how far we can travel into the stars.
Owner of "The Grand Voyage" addon series
Collaborating with Dangerous_safety for the still developing Cer system
Owner of "The Grand Voyage" addon series
Collaborating with Dangerous_safety for the still developing Cer system
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Topic authorSevenSpheres
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Looking into it again, it seems like normal maps converted using GIMP are good enough. The difference is hardly noticeable.
4K Tethys normal (credit to fyr02)
4K Tethys normal (credit to fyr02)
My Addons: viewtopic.php?f=23&t=19978 • Discord server admin
Celestia versions: 1.5.1, 1.6.1, 1.6.2, 1.7.0, and some unofficial versions like Celestia-ED
Celestia versions: 1.5.1, 1.6.1, 1.6.2, 1.7.0, and some unofficial versions like Celestia-ED
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i see horible colorbinding at the northSevenSpheres wrote:Looking into it again, it seems like normal maps converted using GIMP are good enough. The difference is hardly noticeable.
There is a limit to how far we can travel into the stars.
Owner of "The Grand Voyage" addon series
Collaborating with Dangerous_safety for the still developing Cer system
Owner of "The Grand Voyage" addon series
Collaborating with Dangerous_safety for the still developing Cer system