Celestia Forums

I've been looking, but I can't find anything....

How does one make a cloud texture? Especially a realistic one?

I've tried getting maps off of Lunar cell (which would be especially nice considering all of the lovely hurricanes and tropical storms out there right now), but there are distorions in it that can't be straightened out.

...John...

I still havent found the best way to make clouds look like the real thing so I tend to use this source which is updated every 3 hours...You can extract the whites out of the image by deleting the blacks...

http://xplanet.sourceforge.net/clouds.php

That is a GREAT site!

However, I'm not quite certain how to subtract the dark areas. I've tried selecting certain hues and transferrring them to a transparent image, but I can't get all of the detail that way. Perhaps Paint Shop Pro isn't the proper program to use. I have Photoshop (one of the latest versions, I forget which, though), but I use it so rarely, I'm not familiar with it at all.

Looks like I have quite a bit of homework to do!

...John...

There is an option in the menu 'select' that is called 'color range'. Select the black color and then delete it... I think thats the way...

Ooo... I'll check it out when I get home. thanks!

...john...

Dollan wrote:However, I'm not quite certain how to subtract the dark areas.

Have you tried using a completely white image of the same size, and then use the clouds as the alpha-layer? Maybe you have to Invert the alpha-layer.

Harald

Wonderful! I've figured it out! Now I just need to play around with fine-tuning the various options for good results, but all in all I have it worked out.

I suppose making ring textures is much the same. But that is for a later time!

Thanks for all of your help, folks!!

...John...

The select color range never works out right for me. The is always a bunch of left over garbage left behind.
I am planing on revising the tutorial that was released several years ago and adding my own tweaks to the info. I still think making them in GIMP is the best way to do it.
If you do a search here on the site you should be able to find the old tutorial laying around somewhere. I know that Fridger has made one and I can't remember you did the other one. Give them a try for the best clouds or just wait a little while longer for my how to.

Don. Edwards

Don. Edwards wrote:The select color range never works out right for me. The is always a bunch of left over garbage left behind.
I am planing on revising the tutorial that was released several years ago and adding my own tweaks to the info. I still think making them in GIMP is the best way to do it.
If you do a search here on the site you should be able to find the old tutorial laying around somewhere. I know that Fridger has made one and I can't remember you did the other one. Give them a try for the best clouds or just wait a little while longer for my how to.

Don. Edwards

I definitely agree with Don and with Harry above. While the 'select by color' tool is powerful in general, it newer retains the subtle and crucial diffuse boundaries of the clouds! In my experience the best way is to import grayscale cloud photos from satellites as alpha channel of a RGBA 4 channel (A=alpha) image. It then depends what one wants to do with the 3 remaining R,G,B channels. One possibility is to put on some bluish haze layer that e.g. becomes stronger towards the poles in form of a vertical gradient. It is then an important matter of correctly normalizing the intensity level of the alpha channel image, since that crucially determines the amount of transparency of the pattern...

At the end, one might consider adding carefully a small amount of 'bump mapping', taking again the original bw photo as the 'bump reference', e.g. in GIMP. After the 'bumping' process, I usually add some amount of Gaussian smearing (10-20 px) to the whole RGBA image, since the resulting impression of "fluffyness" is most essential and also counteracts the unpleasant 'pixelation', if the clouds are viewed from relatively close distance...

Bye Fridger

too bad, I forgot to logon with my new office machine;-))

Bye Fridger

I agree with Don etc about using the alpha channel over the colour select tool. Furthermore a number of cloud layers combined are usually needed to make a realistic looking texture. For instance the clouds i'm making at the moment have three layers.

1. I started with t00fri's 2k clouds as a base layer ( mostly to preserve his haze layer which i really liked but wasnt aware so much work went to making - all the better : ).

2. The seond layer is a bump mapped cloud layer using the gimp bumpmap filter.

3. Layer 2 is quite dark so the third layer is just a normal cloud map made by using a greyscale cloud image in the alpha layer of a pure white image.

I've found these three layers combined give nice clouds. I have uploaded an 8k version of them to the motherlode.
They can be got here: http://celestiamotherlode.net/creators/dbrady/Clouds_16K_VT_L0_3.zip Dispite the name they are only 8k and up to level 2. I have tried to upload the 16k layer but have failed thus far. My uploads for every month are limited but i'll try again soon. There'll also be a 32k add on for them eventually. Though i'm afraid there are no hurricanes like Don's.

T00fri,
I hope you dont mind me using your clouds in my texture? They were the nicest i found ; ).

DBrady,
Well it sounds like you have nearly worked out how I do my clouds but I have a few more layers to mine. Actualy I stopped using the blue gragiant haze in my clouds because of problems with the clouds over ice and snow. It was making the ice and snow too blue. I have added a slight grey haze layer and adjusted Earth haze coloring and this gives a better result at least for my taste. I do all my cloudmap work in photoshop, meaning the work on the actual texture that is black and white. After editing tweaking, editing adding or subtracting clouds, ajusting brightness and contrast I save the image as a grayscale and import it into GIMP to create the tranparent version. I truely wish Photoshop could do the transparencies the same as GIMP. If it can be done I still haven't figured it out.

Don. Edwards

Yes...I use Fridgers clouds nearly all the time...and then sometimes Don's, just to break it up a bit...Don...your 8k cloud texture is wonderful..I just like to see some animation. In some scenarios you can get a good 3 way dynamic...ie shuttle/hubble/clouds...It's mesmerising...especially after a few ESB's and listening to your fav ambient tracks on iTunes!

More Earth cloud textures please!

Regards...bh.

DBrady:

I downloaded your 16k cloud texture and it is rich and full. I'd like to use it but I have a minor problem. Although it is thick in some places, when I go to a spot below those clouds (say 1 km or less in altitude) and look up, there are no clouds above my head, even though the sky is overcast when viewed from above.

Here are two screenshots to demonstrate that.

This one is above the cloud deck. Notice it is thick and overcast.



This 2nd shot is at the same location but is below the cloud deck. Notice that the sky is clear overhead.



I've tried to move the scene and even fly under the clouds, but I can never get the overhead scene to be cloudy, even when the clouds are there. I've seen this with lots of cloud textures in Celestia, but one of the things I really like about Fridger's original 2k clouds is that you are able to go under them and feel like they are really above you, at least in some locations. I don't know how they differ in structure from yours, but something is mechanically different.

Is there some way to modify your texture to allow it to be drawn overhead, as well as along the horizon, when seen from the side?

Frank

Frank,

Unfortunately i think it may be a bug on your system. Are your drivers up to date? All works fine on my system.
At low altitudes any clouds overhead are perfectly visible.

Ps. The clouds are only 8k at the moment, i havent yet uploaded the 16k level.

It works fine for me with an FX 5200.
I'll try it on my home system (Ti 4200) this evening.

I put the contents of the Zip file into the folder
Celestia/extras/Addons/HiresClouds/textures/hires/
and created the file
Celestia/extras/Addons/HiresClouds/HiresClouds.ssc


System:
512MB 2.4GHz P4, WinXP Pro SP2
128MB FX5200, Forceware 61.76
Celestia v1.3.2 final

System:
512MB , WinXP familiale SP2
128MB FX5200 (nv4_disp.dll)
Celestia v1.3.2 pre10

Bah!...Gforce2 is struggling here!

Regarards...bh.

OK, it looks like it depends upon where you drop down to the surface. The screenshots I provided above were below the thick cloud deck over western Canada. There, the problem occurs even though the clouds are thick and overcast. Elsewhere, however, the clouds do appear over my ground position. I haven't checked everyplace, however.

Here is the cel:url of a location near the screenshots. (I'm sorry, I never learned how to imbed a hyperlink inside a word in a forum post)

cel://Follow/Sol:Earth/2003-03-30T17:52:20.05194?x=U3Yz+IWlXhuuDA&y=lwysCypWKA&z=cZqmMeSPRKAC&ow=-0.827741&ox=0.095411&oy=0.482053&oz=-0.270860&select=Sol:Earth&fov=32.336597&ts=0.000000<d=0&rf=40855&lm=0

When you go to the location via cel, do your clouds appear over you or do you get the same thing I have observed?

Frank

It all appears fine on mine with the cel.
I have a ti 4200 64mb aswell as i think you know.