Thick Atmosphere Glow

[efflux]

I'm starting this thread here because no real file solutions (yet) to demo it but I have pictures I did in Terragen that do show it.

I'm guilty of this as well and I'm going to experiment more with it. When you look at old Terragen renders you see massive use of atmospheric affects because people used to love that effect. This is quite natural in many real world environments. Many TG2 renders are all about details in terrain including trees etc and clear atmospheres yet because we have exr output TG2's capability to use thick glowing atmosphere then post edit to give better exposure and clarity is way higher than Terragen's.

I've included a few old terragen renders I found. In the first picture there is a lot of glow. If I had turned the camera to the right it would be completely blown out but with TG2 and exr this would not be a problem that couldn't be solved. In the second image (just a small test render I found) there is also a lot of glow and very dark ground which once again is not a problem for TG2 and exr. Third image, more masses of thick atmosphere and glow.

The problem is that if you reduce this atmospheric effect to create less glow if say you are pointing towards the sun then further from the sun the scene will look devoid of atmosphere.

[efflux]

Another point worth mentioning is that atmospheric effects are interlinked with the scale you are working on. If you work big then thick atmosphere will obscure closer details. I'm trying to keep everything I work on near realistic scales so each planet has relative scales to the next. It makes importing clip files from one scene to another easy to deal with.

[Tangled-Universe]

I thought I would paste my comment on one of your recent comments on this in the image sharing forum here, since it's about the same topic:

Good start.

This highlights something I'm going to do further tests on in accordance with the whole problem of photography and attempting to compensate for these problems in TG2. I think in a real photo your second image would be massively blown out with light. I'm going to test really pushing for way more atmosphere glow. I don't use any contrast in the render settings in TG2 or try to "fix" exposure which isn't really possible in TG2. I Iet things get badly overexposed (or underexposed) then I post edit it with exr. You can edit exr in Blender which is free. That's a bit convoluted to explain how to do though. It requires nodes in Blender. I may start a thread about this whole topic. Blender actually does do more or less what TG2 can do with exposure but it just gives you options later. Then you export the Blender output to another app (this can be lower bit depth) where you can further tweak diffferent regions of the shot. To me, many TG2 renders look like people are compensating for lighting within their TG2 lighting environment and it doesn't look so photo like because nearly all landscape photos end up being heavily post edited. By doing this you diminish one of TG2s greatest features, it's atmosphere glow. It's the same in movies as well. If you look carefully you can see this editing even in movies i.e ground that has been brightened.

I think I understand a bit what you mean. The default atmosphere settings are quite realistic, I think. One shouldn't tinker too much with it.
Basically the camera in TG2 should emulate a real world camera. In other words: with the default atmosphere settings your render output would be overexposed when facing the atmosphere glow/sun directly.

On the technical side you made one mis-assumption here. The render contrast and gamma settings only apply to lower bit depth formats like BMP and TIF. If you save as EXR the renderer will not apply the toning, contrast and gamma to it.

Another point worth mentioning is that atmospheric effects are interlinked with the scale you are working on. If you work big then thick atmosphere will obscure closer details. I'm trying to keep everything I work on near realistic scales so each planet has relative scales to the next. It makes importing clip files from one scene to another easy to deal with.

That's definitely worth mentioning and very true. If you don't want to fiddle too much with atmospheric settings to control for your scale deviation from real world then just stick as much as possible to real world scales.

I think my latest image is evident of the issues you can get when your atmosphere doesn't completely "fit" the scale of your scene.

[efflux]

OK, I found a file to show you how I do things. Just one of my unfinished planets. There is a moon (hence the name) but you can't see it here. The sky is quite blown out but by no means is this an extreme example. This scene is not hugely glowy. Sometimes the sky is completely white when looked at in the render preview without exposure adjustment but I know clouds are there. The TG2 exposure adjustment in the preview window is very useful. I just output from TG2 as is with no contrast or exposure adjustment. I do exposure adjustment in Blender. Then I apply more post in Lightzone which has algorythms that can analyse shadows, light etc and it has a brilliant zoning system to adjust levels. You can also select areas and colours to treat but I didn't do that here. There will be other apps you can use. Sadly Lightzone isn't developed anymore.

[Tangled-Universe]

Ok, but what is it exactly what you're trying to say/discuss here...sorry I'm ignorant

All I see is over-exposure because the TG2 camera simulates the low dynamic range of a conventional camera, BUT the output *is* HDR and in fact far superior over HDR taken with a DSLR.
In the example you treated the image, rightfully, as an HDR image and compressed the dynamic range into the visible range. So to say.

You mean to say "don't try to make your render look like the final result you're after, but let the glow and over exposure do its thing and correct in post"?

[efflux]

You mean to say "don't try to make your render look like the final result you're after, but let the glow and over exposure do its thing and correct in post"?

Yes, this is what I'm saying. Don't worry if it's all blown out with glow and thick atmosphere with terrible problems of exposure because this is exactly the problems you'd get with a camera and exr can totally adjust that. TG2 can adjust exposure and that is useful but TG2 doesn't need to go too far with these post adjustments because there are other apps to handle that. Also, further editing to change certain regions of the picture is usually needed. Once again, exactly what you'd have to do with a photo but often you'd have to take several shots with bracketed exposure.

This whole thing needs further experimentation but I think it's a problem for new users of TG2. If this type of thing was understood then it's easy for anyone to deal with it via exr and further editing. It just makes for a picture that has all the details in correct exposure. Of course you may not want to go too far with it. Bright blown out areas may be desirable.

I used to think TG2's default settings were too thick and glowy. Now I think that's dependant on the scene. Often it isn't thick and glowy enough resulting in areas further from the sun looking quite devoid of atmosphere.

[efflux]

Here's a shot of how I edit my exr renders in Blender. When you open Blender you will need to click on the window menu at the bottom left and choose Node Editor. Check the Use Nodes button. Also select Image Compositor (the third icon next to Node menu). Add the nodes you see in my screenshot. There are other nodes you can use to do other things. Probably you can do a whole heap of editing within Blender itself but I don't do that. I just change the exposure. On the image node you can load the exr image. At the right, on the render panel, make sure the render resolution is the same as your image size. This is because you need to hit render to get the final image to save. When you do this the window will become the image editor and you have a Save As Image option on the Image menu. You can choose the format.

[Tangled-Universe]

Aha ok, happy to see we're on the same line basically. This is no news actually, without meaning to sound blunt.
However, nobody ever systematically addressed this issue and especially not the way you seem to do often.
I'm curious to what menthods you're going to use and the results you will obtain.

This will be pretty difficult I can assure you. For instance, the atmosphere also has a huge impact on colour saturation, which in turn also affects shadow detail.
There's this very inter-related nature of Atmosphere <-> GI <-> surfaces, which is hard to get your finger on.

[efflux]

I just changed an error on that description but no big deal.

Some people will know what I'm saying here but I think it needs explained because this is a fairly easy to deal with TG2 situation for anybody to try. Since we have Blender which can do the exr editing then it should be no problem for anybody to try.

As for atmosphere effecting colour saturation etc. I've not pushed this in any experiments. However, in most situations you will probably not take this to extreme. It might be worth really pushing it though just for tests.

One problem is that in real life, atmosphere is not all even. In some environments it's totally uneven. That's where low clouds would be used. That gets tricky though. It needs to be subtle. I did low lying mist with clouds on two planets but that is very difficult to get right especially if it's an environment you want to move around in. Then you might get exposure problems heaped on top. Once done though, that is very effective.

[efflux]

Also, what other apps can be used to do final post editing after the exr adjustment? How would you change exposure of ground to sky if the ground is very dark and sky still light? Lightzone can't be got anymore. That's what I use but maybe others will know how to do this sort of thing in standard apps. Photoshop or whatever. I'm guessing there will be ways using layers. You often have to do this with real photos so I think it should be thought about with TG2 as well.

[Tangled-Universe]

As for atmosphere effecting colour saturation etc. I've not pushed this in any experiments. However, in most situations you will probably not take this to extreme. It might be worth really pushing it though just for tests.

Don't underestimate this. You don't need to push it at all(!).
Have a look at this example. It's a minor adjustment in the atmosphere and the difference is quite striking.

Anyway, I'm just trying to say there's more to it than glow vs exposure. This is complicated stuff and therefore there's probably not so much discussion and specific tests on this.

[efflux]

On those two images. The one on the left looks more realistic. the scale appears right. I think that the GI is causing this visual effect. More GI makes thing seem smaller.

[efflux]

The play between atmosphere and GI is probably correct. For example in the UK we generally have dull weather. You just don't see too much light bouncing around unless it's a very bright day.

[efflux]

Just one thing to notice. On my third image after the darker ground compared to sky (even although the ground isn't that dark here) has been corrected, you will notice how the lightzone algo has created a very slight darker line around where the terrain meets sky. I have seen this effect in movies, especially when they've had to severely correct dark ground.

[efflux]

OK, here's another level of difficulty emphasising that we aren't even all seeing the same thing.

I just viewed some images here (in particular Tangled-Universe's image with the tree) on my Macbook. Massively different looking from my Eizo where the colours are much more saturated looking with much deeper contrast.