Some informations about textures (little FAQ)

[jim]

Hi all,

This post shall help to unterstand better how textures are used in Celestia.

general informations:
- Supported file formats: JPG, PNG, BMP(not recommend), DDS (DXT1c, DXT1a, DXT3, DXT5). Not every grafic card support texture compression therefore check if you can use DDS files.
- Texture dimensions need to be powers of two.
- usual texture dimensions: 1k = 1024x512, 2k = 2048x1024, 4k = 4096x2048, 8k = 8192x4096, 16k = 16384x8192

Which file formats should be used for which map type?

standard texture: JPG, DXT1c, PNG, DXT3
- the alpha channel of PNG and DXT3 can be used for specular reflection.
specular map: JPG, PNG, DXT1c
bump map: JPG, PNG
normal map: PNG, JPG (if only low compressed), (DXT3, but some artifacts)
night light map: JPG, PNG, DXT1c
cloud map: PNG, DXT5

Note:
-Bump maps, normal maps and specular maps works only on modern grafic cards.
-A normal map is a special version of a bump map which is direct used by the grafic card.

More information about map types, it's function and the solarsys.ssc can be found here:
http://members.fortunecity.com/guilpain/index_uk.htm

How is a map installed?

1. Copy the map file into the medres, hires or lowres folder (c:/program files/celestia/textures/). Which folder exact doesn't matter but Celestia tries to load the texture first from medres, then lowres and at least hires the folder. A resolution switch with "shift+r/r" change this order. Of couse the resolution switch makes only sence if the textures are correct placed.
2. Edit the solarsys.ssc (c:/program files/celestia/data/) with notepad or an other editor and enter the map file name at the right position.


How much memory (ram) is needed to use a large textures?

The table shows the peformance dependent on the system memory.



Notes:
- The table is only a clue.
- The values assume that a prober grafic card is used (e.g. 64mb: TNT 16mb, 256mb: GF2 64mb).
- This table is valid for Windows9x. For other (newer) operating systems it's better to increase the memory.
- For a fly from object to object with fast load times there is more memory needed.
- Also with enougth memory there is a significant first load time for large textures.


Now a little bit math:
How many memory space (ram) need a texture?
JPGs and PNGs are small on the hard disc but grafic cards can't process this formats therefore the size of this file formats is in the memory essential more large. The following values for JPG/PNG are valid for texture compression off.

JPG / PNG
1K: 2,66mb
2K: 10,7mb
4K: 42,6mb
8K: 170 mb

DDS DXT1
2K: 1,33mb
4K: 5,33mb
8K: 21,3mb
16K: 85,3mb

DDS DXT3, DXT5
2K: 2,66mb
4K: 10,7mb
8K: 42,6mb
16K: 170 mb

Now an example with earth (the moon must be also regarded because it is visible if you turn the earth):



Note:
- For the best performace all actuel used textures should find place in the texture memory of the grafic card. This simple example shows also that a GF4 with 128mb can get a little bit stress.
- Other parts of Celelestia, other runing software and the operating system need also memory space!

Sorry my english is not the best ;-)

Jens

[Darkmiss]

Excelent Post Jim, well done.

Quick Question
I am useing a Dxt3 earth texture
and a Dxt5 night texture
is this wrong ?

Going by your list up there
would they be better with both at Dxt1c ?

If so what would be the diference ?

[jim]

Hi Darkmiss,

Now DXT3 for earth texture makes sence if you use the alpha channel for the specular map. Otherwice i think it's better to use DXT1c format. For the night texture is the DXT1c the best choise. With DXT5 is only wasted space.

I think it's better to say some general things about the different DDS formats.

DXT1c:
- only color (no aplha channel)
- compression 8:1
- reduced color depth (16bit) on Nvida hardware (not sure if ATI has the same problem)
This format is good for all surface textures, night lights and secular maps. The color reduction is insignificant most times.

DXT1a:
- uses 1 bit aplha
- see DXT1c
I found no use for this format because the binary alpha looks ugly.

DXT3:
- 4 bit alpha (that means 16 level)
- compression (only) 4:1
- no color reduction
With this format you can save surface and speculare texture with only one file. I would this recommend if the color reduction of DXT1c is a problem. Otherwice it's better to save surface and speculare texture into different files because you are more flexible.
At the moment i use this format also for 8k normal maps but i hope future versions of Celestia support 8 bit palleted DDS files.

DXT5:
- interpolated alpha (that means more then 16 level)
- see DXT3
This format is good for cloud maps because the interpolated alpha allows a more soft transparency.

Bye Jens

[kary]

MY ANSVER AND ALL ABOUT IT WAS MOVED TO

http://www.shatters.net/forum/viewtopic.php?p=17003#17003

[jamarsa]

...

[ElPelado]

in your code, you have both "bumpmap" and "normalmap".
i'm not an expert, but i think that you cant use both, or normal or bump. and the other thing, i dont know if you can use *.jpg textures ni normalmap

[danielj]

How do I know if my DDS textures are DXT1 or DXT3 or 5?Other thing,since I am using Windows XP,would be recommended to increase my 256 MB DDR 256 RAM memory?

[jim]

How do I know if my DDS textures are DXT1 or DXT3 or 5?

There is no simple way to differ between dxt1 and dxt3/dxt5 compressed files. If you know the dimensions of the map then you can use the file size. A dxt1 map file has the half size of the same map with dxt3 or dxt5 compression.
e.g.

8k map (8192x4096), dxt1: 21,3mb, dxt3/dxt5: 42,6mb
4k map (4096x2048), dxt1: 5,3mb, dxt3/dxt5: 10,6mb

Other thing,since I am using Windows XP,would be recommended to increase my 256 MB DDR 256 RAM memory?

Now you can live with 256 MB but Celestia works faster with 512MB or more especially with large textures and the large star database. I would recommend to upgrade at least to 512 MB.

Bye Jens

[Silver Surfer]

Hi Jim

I'm new in there, but if you don't mind i have a question for you.
I use a Bi-Pentium III 800 Mhz with 1Go of Sdram133+a Gforce3 Td.
Would i be able to use 8k DDS texture? I'm actually using a 4k DDS for the earth and this is very fast, there's only a small "lag" the first time the earth is loading...

The question is: Is Celestia able to load 8K texture in a Gforce3 who seem to be limited to use 4k textures...

Your post is really impressive.

Silver Surfer.

[jim]

Hi Silver Surfer,

With your system you should be able to use every large DDS texture also 16k! But even the fastest sytem will need a bit time to load textures from the harddisk to the memory. You should try the virtual textures with the latest Celestia pre release. 32k Earth and more is possible (see in the forum).

Bye Jens

[Guest]

what is the difference between a normalmap and a standard texture

[jim]

what is the difference between a normalmap and a standard texture

http://members.shaw.ca/jimht03/normal.html

Bye Jens

[Ton Lindemann]

Hello,

I'm a brand new user of Celestia. A very nice program with great options. But I'm not happy with the next link. It offers not only texture information, but also commercial and agressive dialerlinks (with spyware I guess) pops up. Only to close by Alt-Ctrl-Del and next with closing IE from the list).

http://members.fortunecity.com/guilpain/index_uk.htm

Cheers,

Ton Lindemann

[selden]

Tom,

You need to upgrade the version of Internet Explorer that you're using. The current version blocks popups. Alternatively, you should convert to using Mozilla Firefox.

Unfortunately, many free Web servers do the things you complain about. That's how they make money to pay for the "free" disk space.

[Tetzauh]

I'm sorry to ask this question , it will probably strike you as silly... but I Have no idea what DDS texures are made with or how to edit them. I need to edit them because many add ons have them (like blue marble or green mars) and I think they're probably 2K, because my card won't show them. I had the same problem with JPGs and PNGs and I just resized them to 1k and that was it. But DDs strikes me as odd format. I use ACDsee 3.1 Do I need to upgrade or migrate to Corel or Adobe?