Celestia Forums

I was watching the clouds go by -- in Celestia -- when I realized that the static images were rather boring. So today I am here to brainstorm some ideas about clouds (pun intended but probably regrettable).

1. Alpha Channels -- is it possible to make the clouds fade in and out somehow? I mean is it possible to change the alpha of a dds file or whatever allows alpha like, on the fly? I know it can be done in Quake so I assume it can be done in other 3D OpenGL programs. It would be cool if the cloud texture could fade or strengthen slowly (and not too noticeably).

2. Animated clouds -- I don't know if this is possible or not but again, lots of video games have animated textures in them, some with quite long and complex sequences. I'd have to assume that some good satellite footage exists that could be used as an animation with a little artistic knowhow.

3. Spontaneous cloud animation -- eliminate the textures completely and go for some special effect instead. I've seen a few screensavers that can generate random smoke and cloud stuff that looks pretty convincing, and again some 3D video games seem to be able to hack out some types of clouds fairly realistically. It would be especially cool if it was built-in to Celestia and you could choose your own "cloud pattern mix" where you can have presets by "type of planet" or do your own thing and change color, violence, frequency of lightning, etc. Yes, LIGHTNING!

Anyhow these are not yet feature requests, pending comment from knowledgable people.

Hi Size_mick

I'm not in the developement team but I think that I should give you an answer.

You requests are interesting but are very very difficult to implement.
The algorithms for realistic clouds dynamic runtime generation are available.
There are several OpenGL demos that can simulate clouds, but are optimized for surface rendering, so when the observer is under the clouds.

To map a random generated cloudmap around a planet is a completely different thing. Brobably it is feasible but the CPU overload should kill the application.
Moreover Celestia has the time speed feature. It will be almost impossible to keep realism of clouds evolution when the time reaches a critical speed that causes the cloudmap regeneration each frame.

So I think that this feature won't be available in Celestia for a loooong time.

Bye - Paolo

Heh the post was here for a day or two, empty. I was afraid my ideas were so ludicrous that people didn't bother replying because they thought they were just completely stupid. Maybe they are, maybe they're not.

What about the idea of using animated textures?

What about cloud VT textures?

Hey there...

I probably should just keep my mouth shut - since I manage to get in trouble almost every time I say something - but here's a thought for ya:

As is done with Venus, couldn't you define a "surface" for a gaseous planet (like Jupiter) and then just display the outer layers as a cloudmap?

I mean, I really don't know what liquid metallic hydrogen looks like, but it ought to make for an interesting display when you peel back the clouds from Jupiter.

Another thought... If you can add one cloudmap, defined at a certain altitude and with certain properties, couldn't you simply add another level of detail using another cloudmap?

Just a thought.

Take care, Bob

What I have been keen to try for sometime, but haven't got round to yet, is finding a source of real clouds on the Web, which I could use to continually update my Earth cloud texture.

I'm sure I have seen meteorological sites with whole Earth maps of cloud cover. We could display real clouds if a) we could find a way to download these images automatically; b) had a small application to re-format the images into a suitable form and place them in the textures folder with a date stamp. Celestia could display the latest image, or could be extended some way to load several different version into memory so it could animate them if we go back in time.

Has anybody tried this yet?
Does anybody have any ideas about how easy or difficult it would be?

Adam

How about checking this site and the related link,it looks like a good bit of work to clean up the image but it might be fun to try
http://personal.southern.edu/~dascott/tutorial02/cloudcomp.htm
Cheers Jestr

Thanks very much for the link Jestr. The source of global cloud images wasn't woking but I found an alternative here:

http://www.sat.dundee.ac.uk/

My first, v. rough and ready use of real clouds is below:



Converting this one took seconds (I know... it looks like it ) I suspect though that we could do better than that and automate the process too.