Celestia Motherlode-Normal map scales?

[Kolano]

I believe that most normal maps for earth, but likely for other objects also, have been scaled to give a more signifigant visual impact. Could this scaling factor, or at least an estimation of, be listed with each availible normal map texture on the Celestia Motherlode site?

[Harry]

BTW, the scaling for my normalmap is described here:
http://www.h-schmidt.net/celestia/earth-vt/
It's 160 for level5, 80 for level4, and so on.

Harald

[Kolano]

Harald, Does that mean it's scaled to less than the real height at level 4? Or is it 80x the real height, which seems like a huge scaling factor?

Also it sounds like this may be more complicated for certain textures than I anticipated. I had thought it would be a simple single value like 2x, 5x, 10x.

[maxim]

Shouldn't the height factor decrease with level depth instead of increase???

maxim

[Harry]

Harald, Does that mean it's scaled to less than the real height at level 4? Or is it 80x the real height, which seems like a huge scaling factor?

I may be wrong (can someone who knows this stuff comment, please?), but IIRC the height was originally in meters from 0..65335, this value is divided by 65536 and multiplied by the scaling factor to get the value which is combined with a unit-length to create the normal.

The width of one pixel is about 1km, so a scaling factor of 65 should give "real height" for a 32k texture. For level4 a pixel has a width of 2km, so you only need half the scaling factor.

So 160 is about twice the real height, I had to use a value which I could divide by 2^5 (160=5 * 2^5).

Also it sounds like this may be more complicated for certain textures than I anticipated. I had thought it would be a simple single value like 2x, 5x, 10x.

You could convert the whole image to a normalmap (with only one scaling factor, in this case 160), and then rescale and create the various levels, but I don't know if/how this affects the quality.

Harald

[wcomer]

Kolano,

It may be safely assumed that all of the normal maps have heights chosen for aesthetics. I experimented with 64k true-normal maps for the earth and they are pretty dull. Also, the original BlueMarble texture that was used for most of the high resolution VT's had a strong shadow effect added which made enhanced normal maps a necessity. Unfortunately the nm16 tool that most people used for the creation of the normal maps does not take true bumpheight multiplier as an input rather it takes another factor altogether. Consequently I suspect that most of the normal map authors do not know what their true scale factors are. I will reply later with a conversion formula for going between the nm16 bumpheight and the effective multiplier (which I believe I have posted before in another thread.)

cheers,
Walton

[Kolano]

wcomer-"It may be safely assumed that all of the normal maps have heights chosen for aesthetics."

I realize this. I'm just hoping to be able to get a better idea of how off from reality they are. I'd assume others here would be strongly interested in this too, since aligning with reality tends to be a priority.

[John Van Vliet]

well i can't speek for all, but my normal maps have been set to
1) the lowest piont [ earth] -sealevel to "0" and everest to "65335 "
[mars ] val. mar. 0 olympios mons 65335
2) then on all levels for the virtual tex
level 5 100%
level 4 50%
level 3 25%

using nm16 to make the normal from a 16 bit gray

[John Van Vliet]

hi Harry but i have found that anly making a 32k normal and then resizing it dose not work
with every size smaller the mountains get twice as big
so a normal neads to be made from a smaller bump map
and the height neads to get cut in half

[maxim]

Hm... what software are you using for creating a normal map?
Not the nvidia toolset I presume.

maxim

[Harry]

hi Harry but i have found that anly making a 32k normal and then resizing it dose not work

Thanks for trying. There must have been a reason why I took the slower and more complex route, just couldn't remember...

Maxim, I've used Chris' nm16 to convert from 16bit heightmap to a normalmap. Here it is:
http://www.shatters.net/~claurel/normalmap/
But I had to slightly modify it, IIRC because of some probem with signedness.

Harald

[don]

Could this scaling factor, or at least an estimation of, be listed with each availible normal map texture on the Celestia Motherlode site?

Howdy Kolano,

When you have a question regarding the Celestia Motherlode web site, which is a privately operated, 100% volunteer web site, it would be best to use the Contact form available on the web site. This way, your question will be answered by someone who runs the site.

To answer your question directly, the Celestia Motherlode web site is only able to list the information provided by the add-on creators in their add-on submission message. If the information is not provided with the add-on, then it can't be listed.

Cheers,

-Don G.
Celestia Motherlode Volunteer

[Guest]

Thanks for the reply Don.

I'd suggest that a set of "submission info suggestions" be added to the motherlode site somewhere. Though you don't want to restrict what folks can submit, such sugggestions would help in gathering a normalized set of data for things.

[Kolano]

er, that was me. I really need to register here.

[don]

The next version of the Celestia Motherlode web site will attempt to gather much more information from the add-on creators.