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Yes, I know we've long been lobbying for more cloud layer features. It's just that someday I'd like to see something like this in Celestia.

selden wrote:Yes, I know we've long been lobbying for more cloud layer features. It's just that someday I'd like to see something like this in Celestia.

http://grin.hq.nasa.gov/IMAGES/SMALL/GPN-2000-001065.jpg

Nice! I agree...

Bye Fridger

selden wrote:Yes, I know we've long been lobbying for more cloud layer features. It's just that someday I'd like to see something like this in Celestia.

I have this idea that bumpmapping and cloud shadows can be done only with shader progamming by useing alpha infomation of the cloud map. But only Chris knows if this is possible without to use additional textures.

Bye Jens

jim wrote:

selden wrote:Yes, I know we've long been lobbying for more cloud layer features. It's just that someday I'd like to see something like this in Celestia.

I have this idea that bumpmapping and cloud shadows can be done only with shader progamming by useing alpha infomation of the cloud map. But only Chris knows if this is possible without to use additional textures.

Bye Jens

If you were content with monochrome clouds, it would be possible to pack both a normal map and an opacity (alpha) map into a single RGBA texture. I've meant to experiment with cloud bumpmaps for a while now, but have yet to try coding it. As for just storing the alpha channel and letting Celestia derive the bump/normal map, my intuition is that it would produce unsatisfying results compared to pregenerating the normal map.

--Chris

Chris,

Have any intuition about the results of having Celestia generate bump/normal maps for surfaces at run-time from DEM data, rather than pre-generating them?

- Hank

HankR wrote:Chris,

Have any intuition about the results of having Celestia generate bump/normal maps for surfaces at run-time from DEM data, rather than pre-generating them?

- Hank

I don't see a big advantage to having Celestia do it at run-time, beyond a slight convenience for add-on creators. The drawback is that it would increase the time required for loading the textures. Better to have to do the conversion to a hardware friendly format just once rather than every time you run the program.

--Chris

Chris,

My thinking was that the DEM files might load faster than bump/normal map texture files because there's only one component (elevation) to read off the disk. Saving the extra disk reads would offset the numerical calculations needed to generate the normal vectors.

Also, if DEM files were available, they could potentially be used to generate 3D surface meshes for rendering the surface from low altitudes.

- Hank

Isn't the Alpha channel of cloud textures already used up for transparency? I don't think bunp map data can be stuck in the same texture. It will need to be seperate like the planets.

I think Chris means you need one colour channel for the monochrome clouds, two for the normal map info and the alpha for transparancy. This would be great!

Earth cloudmaps are monchrome even if the are in rgba format. Sure some of us add a slight color layer to help augment the haze sentings. That is what I did for my 8k clouds. But my master version of the 8k cloudmap is totaly clear of all color and haze. So pluging in the normal map should be simple in this case. Now if we can just get it implemented along with real cloud shadows instead of my ah trick this would be nice.

Don. Edwards

An 8k texture done for another sim, with the Blue Marble greyscale clouds used to bump map a flat cloud-white field, then again (with an altered value curve) to produce an alpha layer. Obviously, the mid-morning shading isn't appropriate for the noon-time sun. Surface textures are 16k orbiter default for land and space-graphics 8k at sea.

http://home.ripway.com/2003-12/42359/bluemarbleearthcloudslevel8-2.jpg

Just posted to give an idea of what bumpmapping might do for clouds far from the terminators.