Clouds casting shadows(Static)

Nameless · Post #1by **Nameless** » 08.03.2003, 00:42

After downloading a demo of splintercell, and withnessing it's amazing lighting & shadow casting effects, i came up with this idea.
I pasted my cloud map over a colour inverted, blured, offset version of them to come up with a cloudmap with static shadows.
Here are some pics...

comparison for above...

and my old favorite cloud...

Are real-time shadows a possibility for a future celestia?

Sum0 · Post #2by **Sum0** » 08.03.2003, 13:21

Very nice! Makes them stand out nicely.

Psykotik · Post #3by **Psykotik** » 08.03.2003, 14:08

Amazing ! It looks really great !

Nice done

Don. Edwards · Post #4by **Don. Edwards** » 08.03.2003, 16:08

Nameless,
The effect is cool but way out of scale. For clouds to have a shadow like those in your pictures you would need to go down to the 10 kilometer level. Meaning you would have a area only ten kilometers square on your screen for the clouds to have shadows like that. It is a very good effect but I would consider bringing the shadow much closer to the clouds themselves. Clouds on Earth simply are not at the altitude to make shadows like that. Sorry for the critisism but everything about Celestia is SUPPOSE to be as acurate as posible.

Nameless · Post #5by **Nameless** » 08.03.2003, 17:43

Don,
Thats what i thought (although i think your 10km calculation is way off).
Smaller offsets just dont show up much.

Does that mean that real time shadows havent been implemented because they wouldnt actually be visible?

Don. Edwards · Post #6by **Don. Edwards** » 08.03.2003, 18:01

Nameless,
Sure I think they would, only at a much closer level. They would probably be more like the drop shadow effect that we have useing but they, the shadows will shift under the clouds according to were the sun is positioned. Thats the other major problem with your present idea. The shadows are locked in one direction. So if the sun is to the left there fine but if you change perspective with the sun to the right then your shadows are on the wrong side of the clouds and bellieve me that will start to bother you after a while. Thats why in the clouds I am trying to put together they have omni-directional shadows. Meaning there is just enough shadow on each side of the cloud to trick the eye into thinking the shadows are placed right. Now you can see why its taking me so long and why after almost 3 weeks at it I have taken a break to do a few other things I have been meaning to do. But please keep experimenting. Your reversed color cloud deck is something that was put into that last set of clouds I released. Thats were the depth came from.

If we keep throwing ideas back forth we are going top come up with something that everyone is going to go for. Its taking the time to keep playing with layers, shadows, and the bumpmaping. Keep up the work though.
Don.

jim · Post #7by **jim** » 08.03.2003, 20:31

Hi nameless,

the idea is good but not realistic. Look at some NASA photos made from the space shuttle. The shuttle operates usual in an altitude of only 250 km. At this close distance you can see sometimes cloud shadows. That means for celestia with 8k clouds i think the effect is maximal 1 pixel in size.

But your cloud map looks really nice (without shadows).

Don, 10 km? I think 100 km or more.

Bye Jens

Don. Edwards · Post #8by **Don. Edwards** » 09.03.2003, 06:43

jim,
Your are probably right.I was petty darn tired when I wrote that. 100km does sound more realistic. Definetly no less then 50km.

Jango Fett · Post #9by **Jango Fett** » 12.03.2003, 00:43

If anyone is interested, take a look at detailed example of real cloud shadows on Earth surface:

WARNING! High-res image (cca 3 MB)

http://spaceflight.nasa.gov/gallery/images/shuttle/sts-68/hires/sts068-228-081.jpg

This is low-res image:

As you can see, shadows depend on type of clouds. Lower and smaller clouds are closer to the surface and leave strong and dark shadow, while big higher clouds leve weaker shadow. When Chris implement multiple cloud layers, it would be nice to experiment with different types of shadows, as you already want to develop moving shadows...

Rassilon · Post #10by **Rassilon** » 12.03.2003, 01:15

This is using a low resolution texture but this is what Ive been fooling around with in cloud textures...

Tex is 1024 x 512

Rassilon · Post #11by **Rassilon** » 12.03.2003, 01:22

And heres another one more alien looking....Its a luna cell pattern of clouds with a bit of enhancement...

This one looks a bit much on the shadow imo but oh well...

Don. Edwards · Post #12by **Don. Edwards** » 12.03.2003, 10:32

And now for a test everyone. In that picture Jango Fett posted, where on Earth is it?
I know where it is.
My volcanic moon texture is based on this geographical location.
Anybody remember. I took one look at the rust color sand dunes I knew where it was.
Don.

Sum0 · Post #13by **Sum0** » 12.03.2003, 17:47

Nambia?

Don. Edwards · Post #14by **Don. Edwards** » 13.03.2003, 12:11

And Sum0 gets the prize, what ever it might be.
Yes its got to be the south western coast of Africa in the Nambia region.

Nameless · Post #15by **Nameless** » 15.03.2003, 00:03

Rass,
Nice clouds, are they 2 or 1k. You have any earth clouds? I'd like to see what you'd make of them.
Also I tried to upload my clouds to celestial visions but the link you sent me isnt working since you changed the domain name and i cant remember how you to it, could you send me another msg? I looked all over the site for instructions but couldnt find any.

Jim,
I downloaded your clouds and i dont think scaling the 1k side to 2k makes any difference except making for a larger download. Celestia seems to just resize it to 2kx1k as it is still the same shape as a 2kx1k when viewed in celestia. They're good though.
( It might be just my geforce4 thats the problem of course )

Nameless · Post #16by **Nameless** » 15.03.2003, 00:04

Rass,
Nice clouds, are they 4 or 2k?. You have any earth clouds? I'd like to see what you'd make of them.
Also I tried to upload my clouds to celestial visions but the link you sent me isnt working since you changed the domain name and i cant remember how you to it, could you send me another msg? I looked all over the site for instructions but couldnt find any.

Jim,
I downloaded your clouds and i dont think scaling the 1k side to 2k makes any difference except making for a larger download. Celestia seems to just resize it to 2kx1k as it is still the same shape as a 2kx1k when viewed in celestia. They're good though.
( It might be just my geforce4 thats the problem of course )

jim · Post #17by **jim** » 15.03.2003, 11:26

Hi Nameless,

I have tested if there is a difference between 2kx2k and 2kx1k clouds and beliefe me it's a big difference. Celestia doesn't down scale a texture if OpenGL info reports that this texture size can be handled by the grafic card. Your GF4 should work with 4kx4k textures. Can you build clouds with this resolution and show some shots? I would look envious at this pictures ;-)

Bye Jens

My system: Win98SE, Duron900, 512mb, Geforce2 ti200 64mb

Don. Edwards · Post #18by **Don. Edwards** » 15.03.2003, 16:24

oops
never mind

Nameless · Post #19by **Nameless** » 16.03.2003, 00:14

Jim,
I already built some 4kx4k clouds but they looked exactly the same as 4kx2k.
I put 4x2 in medres and a 4x4( built from scratch not just resized ) in hires so i could compare them-they looked pretty much identical.
What leaves me to beleave celestia rescales them is that the 4x4k is the same size ie. not elongated in any way compared to a 4x2k texture.

Don. Edwards · Post #20by **Don. Edwards** » 16.03.2003, 06:05

Nameless,
Thats because Celestia is resizing the 4 x 4k texture to 4 x 2k. So there is no reason to even do it. A 2k x 2k texture might be stretched to 4 x 2k but I don't think this is what is going on here. We need to here from Chris about how Celestia does it resizng.
Don.