New Maps of Ganymede and Callisto

[Ortolan]

I 2nd Pixel's vote for a more efficient way of encoding the specular channel.

[chris]

My opinion for that matter:
Personally i think that "official ultra-pack" is just too early. I suggest to call it "high-res pack" that contains texures not bigger than 2048x1024 (2k) in both 'dds' and 'png' versions. Exception could be done only for Earth(4k max): 8k + alpha is still 43Mb dxt compressed file!!!
My point is that Celestia is still not capable to map clouds and bump-maps bigger that 2k. So, our static bumps and 2k tweaked clouds could in future make damage to Celestia. And also specular and bump-maps still can not be run simultaneously.
Also i think that the additional alpha channel to base texture is used rather inefficient in Celestia. An usual specular map is just B&W data that doesn't need even to be in the same resolution as base texture...but now it increases size of dxt3 file by factor of two. So i vote for separate specular mask file (or at least adopting dxt1a - 1bit alpha) and/or method for specular lighting that even don't require any hardware extensions or shaders. I can wait for these extras for years when everybody will have 128Mb+GPU graphic cards as minimum.

There are lots of things to consider here . . .

First off, bump maps look like garbage when they're compressed. DXT1 is just not an option for them. Probably the best thing to do is to use palettized textures for them (this is what Doom 3 does); this will give a 4:1 compression ratio. Without this, the largest practical size for bump maps is 2048x1024.

One current limitation of Celestia is that bump maps need to be the same size as the main texture map. The workaround for this is straightforward, so 1.2.5 will not share this restriction.

The advantage to keeping the specular map in the alpha component of the texture is that it reduces the number of active textures required. However, I think that I will make it possible to separate the specular map and the specular map. This allows the use of a lower resolution specular map along with a DXT1 color map. It will also make it much easier to author specular maps.

I will make it possible to do bump and specular maps simultaneously in 1.2.5, with the restriction that the bumpy areas are not glossy. This covers most cases--planets with oceans and planets with smooth icy plains. I'll put off glossy bump mapping until 1.2.6 or when someone wants it..

Cloud maps larger than 2k are tricky because I use the texture transform matrix for cloud motion; I don't have a good workaround for this yet.

--Chris

[Guest]

To Chris,
the additional parameter "SpecularMap" could be just extension to existing handling. I have a remark about clouds as well - another good extension . If i supply a cloud-map with size less than size of main texture it will be better Celestia to replicate clouds instead of streching them up. In this case we can save ram and disk and can get very high res clouds. Ofcourse the look and feel will depend of the autors of clouds.
Best regards,
Pix.