Celestia Forums

For those that know
I have been experimenting in converting my textures to DDS files

I think I have done right, in converting them to DXt5

but what are the diferences between the DXt 1 - 5.

My initial thought was that DXt1 is compressed and 5 is not

Darkmiss wrote:For those that know
I have been experimenting in converting my textures to DDS files

I think I have done right, in converting them to DXt5

but what are the diferences between the DXt 1 - 5.

My initial thought was that DXt1 is compressed and 5 is not :?:

Why did you chose DXT5?? You are loosing this way most of the advantages of the DXT format.

Normally: RGB => DXT1c (8:1)
RGBA => DXT3 (4:1)

A is alpha that may contain bump, spec, etc info.

With the newer Celestia, it is much more advantageous, to use RGB (DXT1c) for the main texture as well as for the /separate/ spec and nightlight textures. It is important to realize that one may usually chose a much lower resolution for the spec texture than for the main texture. This SAVES LOTS of STORAGE. The separate bump file does not work (yet) with DXT and gives best results in *.png format, but *.jpg also works fine.
The nightlight texture also works fine with fairly low resolution.

Since clouds must be semi-transparent, you need DXT3 (RGBA) here, but fairly low resolution works well here, too (2k).

Bye Fridger

Wel I'm really not that advanced yet to start worrying about multiple textures, spec maps, and alpha channels and what not.

as I said im just starting to get into, just converting some if my normal flat textures just so they load up faster in Celestia.

specs and alphas and stuff is still a bit beyond me, but im getting better at this stuf slowly

I had a nice jupiter textue at 4096 resolution JPG, so i converted it to TIFF and then used the Nvidia tool to convert to dds dxt5
I chose dxt5 as i was under the impresion it was the least compressed, or not at all.

also I converted it, because I thought it was the fastes format to uncompress in Celestia.

You are both right of course. DXT5 does the least amount of comprsion while DXT1 does the most. There can be some loss in detail at such high compresion levels though. Thats why I so far have stayed to DXT5. I am going to experiment DXT3 to see how that looks. One of the main reasons Fridger uses the higher compresion levels is that he was stuck on a modem conection and it took a long time to upload realy big .dds files. Hence using the higher compresion help him keep the size down. He also has an older video card, GeForce2 32meg I believe so he was limited to keeping texture size and total .dds size down because of this. Howerver those of us with the higher power GeForce family of cards and with up to 128 megs of VRAM we can afford the lower compresion of the DXT3 and DXT5 formats. I am almost totaly converting everything I can to .dds just for faster load times. And of cousre we know that some of the textures I make are quite big even with DXT compresion.
Now for what was said about specmaps being able to be of lower resolution. I have found that the lower the the specmap res or size the efffect along coast lines starts to sufer. I would hold as a rule that if you per say using useing an Earth texture of 4096x2048 that you shouldn't consider using a specmap any smaller than say 2048x1024 or half the resolution. any smaller and you end up with missmatches in the textures.
But then again I do not use seperate specmaps simply because it takes more VRAM then pluging the specmap into the main texture with GIMP.
I was one of the early members that had trouble doing this and after Fridger's instructions I was finaly able to do it. Another reason to build the specmap in is its better for newer users. They don't have to worry about modifying so many line in there solarsystem.ssc file. The fact that simply changing one line in the .ssc can give them both a new texture and a working specmap can't be looked over. In the end its all a matter of choice. I choose to intergrate as much as posible into the textures I make so that there is more of a bang for the buck even though the stuff is free.

Thanks Don. Im still using your Earth texture
because I love the fact that it has the spec map built in

up to now I havent used any bump maps at all
because of my Gforce 2 gts 64 card just has a bit of trouble

but ill soon have a 128 GF4, hopefuly by this weakend
then ill see how it runs with them too

Thank you both for your information