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Help locating certain cloud textures

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Help locating certain cloud textures

Postby gsagostinho » Thu Jan 07, 2016 10:19 pm

Hi all,

I would like to (attempt to) improve two cloud textures that particularly bother me, but I just can't find where the png files containing them are located! Can anyone give me a hand?

About the clouds: most of our clouds are quite beautiful photorealistic images, but these are either from a bad source or were created in GIMP using some brushes. They look really out of place IMO. The first one is the "cigar" type of cloud that appear in the bottom of cumulus cloud complexes, for instance when using the High Pressure scenario:

Image

The other is the overcast cloud that appears often when using Core of Low Pressure scenario:

Image

Any help would be appreciated.

Cheers!
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Re: Help locating certain cloud textures

Postby ludomotico » Fri Jan 08, 2016 12:32 am

The second kind of clouds look like mammatus, and they are extremely beautiful when you find them during the sunset in real life.

Image

(This photo is not mine and it is obviously "contrast-enhanced", but I have a couple of photos of these mammatus clouds in my archive)
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Re: Help locating certain cloud textures

Postby MIG29pilot » Fri Jan 08, 2016 1:22 am

Yes I have often seen skies just like pic #2.
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Re: Help locating certain cloud textures

Postby gsagostinho » Fri Jan 08, 2016 2:27 am

Well, I am not saying I wish to necessarily and completely change the overall look of the clouds, I just plan to try to improve on them (not even sure if I will come up with something good). But anyway, I also have seen these sort of mammatus clouds in RL and they are very beautiful indeed, but I don't think a simulator should have them as the default cloud for when the sky is overcast. My guess is that these textures weren't intended to be this type of cloud, I think they are just not very good textures (or rather, textures which can be improved a lot). For instance, if you look towards the horizon on the second picture of my post, you can see how they just look like brushes in GIMP. On the top they are quite fine, but still could be improved. Probably something a little bit more elongated and with more structure to it would look better, e.g.:

Image

of even a lot of structure to it such as this:

Image

But still those bother me much less than the cigar shaped clouds in the first picture, here are two different angles showing them. I just think they don't fit at all with the other beautiful textures...

Image

Image
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Re: Help locating certain cloud textures

Postby Thorsten » Fri Jan 08, 2016 6:46 am

For historical reasons, cloud textures are in /Models/Weather/

The second pic seems actually okay to me.

I think there's problems with both these types of clouds, but I don't think they're with the texture sheets.

1) depicts a flat bottom of mature Cu clouds. The sprite is intended to be seen from below only, and the cloud generation algorithm makes sure that it is placed there. Unfortunately (or fortunately), Stuart later designed a LOD algorithm for the clouds which drops a large fraction of the sprites beyond some distance. This created a situation where the bottom sheet can regularly be seen exposed from the side, or even unattached. The texture does what it's supposed to do for the fully drawn cloud and is rather important to get the visuals right for soaring when you spend large fraction of time beneath a cloud. I suspect any proper solution would have to involve tweaking the LOD algorithm to make an exemption for certain types of sprites (I did this for faint high clouds as well).

2) is a generic depiction of overcast layers. Given the way we build 3d clouds from sprites, we can not in fact create a featureless layer as I would like it to be and have a proper edge of the layer at the same time. The current texture is a compromise between these two goals. You can't have a photorealistic sprite from featureless clouds since the original cloud has no division lines anywhere, so it can't be segmented into sprites. Admittedly I can't find fault with the second pic you posted.
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Re: Help locating certain cloud textures

Postby gsagostinho » Fri Jan 08, 2016 4:12 pm

Thorsten wrote in Fri Jan 08, 2016 6:46 am:For historical reasons, cloud textures are in /Models/Weather/


I see, thanks! I also note that they are in rgb format, is there a reason for not using png (besides historical reasons as well)?

As for the rest of what you wrote, I understand your points, but still I will give it a shot to see if I can improve something. The worst that can happen is that I waste 30 minutes of my time :D But about the second picture, what bothers me the most is really towards the horizon where you can see individual clouds looking like GIMP brush strokes. The top is quite fine, though I feel there is room for improvement.

Let's see :D
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Re: Help locating certain cloud textures

Postby Thorsten » Fri Jan 08, 2016 4:16 pm

I see, thanks! I also note that they are in rgb format, is there a reason for not using png (besides historical reasons as well)?


Yes - rgb loads twice as fast, and loading clouds actually is performance-critical, so it's well worth the extra harddisk space.
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Re: Help locating certain cloud textures

Postby gsagostinho » Fri Jan 08, 2016 8:44 pm

Okay, so here are my first tries.

This is the bottom of the cumulus:

Image

And these are the nimbus clouds:

Image

Image

I think these last ones are much better than the default, what do you all think? As for the cumulus bottom, I also think the structured one is better than the default, but for some reason it has a slightly different colour than the rest of the cloud (it looks a bit "yellower" than the others), even though the file is greyscale just like the default was. Is this because of how the light is calculated for these clouds, Thorsten? Or should I attempt to fix this by changing the file to RGB and playing with white balance?
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Re: Help locating certain cloud textures

Postby gsagostinho » Fri Jan 08, 2016 8:56 pm

One more image of the nimbus clouds slightly tweaked:

Image

Image

As for the yellow hue I see in the cumulus bottom, it's also there for the default texture, so nothing to do with my attempt here.
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Re: Help locating certain cloud textures

Postby gsagostinho » Fri Jan 08, 2016 9:11 pm

Two more after some more minor tweaking:

Image

Image
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Re: Help locating certain cloud textures

Postby Michat » Fri Jan 08, 2016 11:58 pm

Howdy.

This is my trick to improved clouds in FG.

1. Open Cloud Image with GIMP - select all - apply filter- enhance antialias. The result is almost imperceptible, but is okay. (does't work fine for trees, need more investigation for liveries and object textures)

2. Open Cloud Image with PSP (paint Shop Pro)- select all - apply filter - fur. The result is quite imperceptible, but is okay.


Thanks.
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Re: Help locating certain cloud textures

Postby gsagostinho » Sat Jan 09, 2016 12:02 am

Well, if the result is quite imperceptible then I am not sure why go through the trouble ;) I think that each unique texture deserve quite a lot of care and I highly doubt that such a batch process can really improve all clouds. For instance, to create these structured nimbus clouds, I took some cumulus clouds, blurred them a bit to hide the structures, darkened them and worked on the bottom edge by making them a bit lighter in tone as well as modifying their shape. This was done individually for all 6 nimbus clouds.
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Re: Help locating certain cloud textures

Postby Thorsten » Sat Jan 09, 2016 7:19 am

Gilberto, the problem is that you've made Stratocumulus out of the Nimbus... They're also (near)-overcast clouds, but their origin is rather different.

The Nimbus textures may not contain the usual 'fluffiness' of Cu clouds because that is an indicator for turbulence in the layer.

This isn't (only) an aesthetic problem unfortunately, I actually want clouds to look appropriate to the atmosphere physics and not just plausible in the sky.

(They're okay for fringing a thunderstorm where the current solution isn't optimal, but not for overcast layers).
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Re: Help locating certain cloud textures

Postby gsagostinho » Sat Jan 09, 2016 1:42 pm

Hi Thorsten,

I totally understand this isn't a simple aesthetic problem but involves representing the correct clouds in the sim. In that case, could you please point out to me how nimbus clouds should look like? When I googled "nimbus clouds" the result looked to me quite similar to the stratocumulus I used as source, but darker. And frankly, I haven't seen a single picture of a nimbus that looks like the default clouds either. Maybe I am mistaking the cloud types, in which case I would be glad to get some correct reference to try again to rework them.

As for the bottom of the cumulus, what do you think about it? And do you know anything about this slight yellow hue that sometimes affect that cloud only in a cumulus formation?
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Re: Help locating certain cloud textures

Postby Johan G » Sun Jan 10, 2016 7:59 pm

I guess the WMO International Cloud Atlas, volume II* (11 MB pdf file) should be one of the better references when it comes to cloud types.

Otherwise there is also the Cloud Appreciation Society. :wink:

* See also the WMO International Cloud Atlas Image Submission Site.
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