earth clouds mip mapping

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Laahel
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earth clouds mip mapping

Post #1by Laahel » 26.06.2002, 08:52

hello everybody

not really a bug, but i wondered if the clouds map was mip mapped like the earth map, cauze, with any resolution map i use ( fre 1k to 8k), there is always the same " blurry" resolution on screen. this don't happen with the earth map, where i can see uge difference betwen maps fros different resolutions.

syste : athlon 1GHz
voodoo 3 3000
Win 98 SE

thanx very much, byeee

Rassilon
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Post #2by Rassilon » 26.06.2002, 15:17

It is because Voodoo cards cannot support more than a resolution of 256 x 256 on textures...
I'm trying to teach the cavemen how to play scrabble, its uphill work. The only word they know is Uhh and they dont know how to spell it!

Guest

Post #3by Guest » 26.06.2002, 17:59

yeah, i know, but celestia use mipmapping on the earth texture, so we can use hi res texture ( i currently have a 8192x4096 map for the earth, very impressive ( and very slow ;p ) but with any texture i use for the clouds, the result is the same for every texture.... i thoug hte texture could be mipmaped too.... it would be very nice....

here are two images:
Image

this one with 8k earth texture without clouds

Image

and this one is the same + your 2k cloud textur rassilion ;p hehe

note how the clouds are very blurry compared to the earth and what they should look like...[/img]

Rassilon
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Post #4by Rassilon » 26.06.2002, 18:15

Unless there was some editing to my clouds that should not be happening...but I am willing to bet that the texture limitations on those Voodoo cards have something to do with it...

Heres how it looks on my computer...Same clouds texture and all...

http://cybermindtraveller.freewebspace.com/pics/earth-new2.jpg
I'm trying to teach the cavemen how to play scrabble, its uphill work. The only word they know is Uhh and they dont know how to spell it!

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Laahel
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Post #5by Laahel » 26.06.2002, 19:35

yeah, i tested on a geforce2 mx on a friend's computer ;p but what i don't understand is why the limits occurs only on the clouds ...... before the entering of the mipmap on the celestia engine, it happened for all the texture, and now, all is ok, but the clouds .... really weird .... it's a little disapointment to have a very detailled earth with very blurry glouds don't you think ? ;p

in fact , what is really disturb me, is that there is not the same thing on the clouds and on the earth....there is allways the little voice who says " why why why!!! you should understand !!" ;p ok for the 256 limit but the mipmap works well on the earth, why did it dont work as welle on the clouds ?? hummmm on day i'll kill the voice ;p

meanwhile, i'll wait for your hi textures of the solar sys and make my ones ( hehehe, my frien has the adsl line, so use his connexion to dl the 21k maps from blue marble..... i'd like to add them your "bumps" of the ocean's floor...)

byyee

Rassilon
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Post #6by Rassilon » 27.06.2002, 21:53

Well I would save your money and purchase a GeForce 3 Ti200 64 Meg...Just dont buy Pine Excalibers...Go with maybe VisionTek...
I'm trying to teach the cavemen how to play scrabble, its uphill work. The only word they know is Uhh and they dont know how to spell it!

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Laahel
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Post #7by Laahel » 27.06.2002, 22:22

i'm saving money for a geforce 4 ti4200 128Mb of ram ( for now ) but i'll instal it probably on an other pc, 'cause, i continue to use my old voodoo3

in fact, i think, i'm wrong with the term of mipmapping. what i was talking of, is se system that allow a card to split a large texture in multiple texture of 256x256 pixels, so cards like the voodoos cand draw the very large textures (like the earth) like the other new gens cards :p, what i don't understand, is why this doesn't work on the clouds if the program use the same split technique... sorry for the misunderstanding...

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Laahel
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Post #8by Laahel » 27.06.2002, 22:25

hop, just re-read the changelog, this feature was aded to celestia 1.2.2


"* Enabled used of extremely high resolution textures through splitting into
subtextures."

like i said, works very welle for the voodoos ;p hihi ( exept the clouds, argh !! T_T )

thanks

chris
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Post #9by chris » 27.06.2002, 22:57

Celestia splits most planet textures into chunks that your graphics card can handle. The largest texture that a Voodoo3 can use is 256x256, so the 2048x1024 Earth texture is split into 32 (8 rows, 4 columns) 256x256 textures. Cloud textures are handled a bit differently because the texture transform matrix is used to make them move over the surface of the planet. This introduces texture coordinates greater than one and means that the splitting trick won't work anymore. So instead the cloud texture is reduced to a size that your graphics card can handle--not typically a problem except for older cards like the Voodoo3 that are restricted to 256x256 textures. One workaround is to actually rotated the cloud sphere instead of just transforming the texture coordinates, but there are some issues with depth buffering that would have to be worked out. There are already cases where the cloud sphere interferes with the planet mesh, and actually rotating the cloud sphere would make them worse.

--Chris

Topic author
Laahel
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Post #10by Laahel » 28.06.2002, 08:18

thank you chris, didn't know how the cloud layer worked.. hehe, you kill the little voice.... i'll see for the next versions, to see what will happen... i'll keep an eye on my voodo3 ;p


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