Feature Request - Atmosphere Sun Vibrancy

Started by WAS, June 01, 2018, 03:21:13 pm

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WAS

June 01, 2018, 03:21:13 pm Last Edit: June 01, 2018, 03:28:51 pm by WASasquatch
A cool feature would be a Atmosphere Sun Vibrancy, which, could be a 0-1 value which effects the vibrancy of the Bluesky Density and Redsky Decay colours. I notice, even in official TG images (at least looks like) and those by our community members and alpha testers, than sunsets, and sunrises, the user often increases the saturation/vibrancy of the Bluesky/Redsky colours to simulate our red/pink sunsets and sunrises.

This effect would somehow (forgive my ignorance in TG programming and math) work off the suns position. The lower the sun relative to the camera/surface/horizon (or post-thought, the sun elevation, duh) the more vibrancy is added. The value for Sun Vibrancy Effect would just determine how much of the effect is applied to the atmosphere Bluesky and Redsky colours.

Naturally, this may work only on one sun, unless the effects could be multiplied/divided together.

Oshyan

What you're describing sounds more like an atmosphere effect, and should be controlled by the atmosphere colors which you've already indicated. Or am I not understanding what you mean? Can you point to the desired effect in an example image?

- Oshyan

WAS

June 02, 2018, 02:31:01 am #2 Last Edit: June 02, 2018, 02:38:27 am by WASasquatch
Quote from: Oshyan on June 01, 2018, 09:11:18 pm
Can you point to the desired effect in an example image?


Sure. But yes, it is an atmosphere effect, based on the elevation of the sun in contrast to the horizon. It's already part of the atmospheres, just it's effect not controllable.

The first image is a default Terragen Sunset/Sunrise (Screenshot_6.png). It already looks great, but IRL, at least around here, and most images I see along the hemispheres of our planet, sunsets give off much more vibrant colours at this elevation, where TG favors more vibrant colour when the sun is nearly gone or already below the horizon (maybe this can just be improved). But this effect would allow people to basically control how much vibrancy is added.

Additionally, the default colours of the atmosphere don't seam to represent real-world colours. Should they not be oranger, and the bias to blue a larger gap (so it's not green). It's hard to come across any images/video of a sunset that is primarily yellow, and doesn't decay to deep reds/pinks. Even to the naked eye. Much like the last image example comparison or your avatar.


Oshyan

The way the atmosphere scatters is simulated fairly realistically. The choice of default colors and atmosphere strengths is of course a specific choice that may not represent what you tend to experience. The colors you see where you are with your eye (you mostly can't trust photos because sunsets especially are often edited) are different in different locations, different times of year, etc. based on amount of particulates in the atmosphere (haze, smog, etc.), latitude/longitude, and other factors. It's been said that the Terragen defaults are sort of representative of what you might see in England, where Matt is from. ;)

Anyway, if you want it to be different, just change the atmosphere values. The capability you want is, I think, already there. No need for another control for it.

I think I see this as having two factors. There is how quickly the color begins to change as the sun gets closer to the horizon, and there is how red or otherwise intense the color is when it changes.

So if you want to make the sun shift to red higher in the sky, you adjust the Bluesky Exp Height (why "bluesky"? because this is *linked* with the red decay; you can see this is in how the Bluesky and Red Decay sliders are linked when you adjust them). The default there is 8000. If you make it 16,000 you'll see the sunset happens higher in the sky, basically. This will have the effect of making the colors more intense *for a given sun height* of the sun.

If you want to make the sun color more vibrant in general, for example if it is very near the horizon, you can increase the amount of Redsky Decay, and/or you can increase the Saturation of the Redsky Decay Color, or otherwise change its color.

Does that address your need? If not I really don't understand.

- Oshyan

WAS

June 03, 2018, 04:03:34 pm #4 Last Edit: June 03, 2018, 04:11:40 pm by WASasquatch
You keep saying "realistic" and such when I'm trying to argue it's not, and it's a little tiresome. I know how light scatters, and what is failed to translate int terragen is If the path is long enough (able to see to the horizon), all of the blue and violet light scatters out of your line of sight. That's how it works here on Earth. This is not represented in Terragen and thus couldn't be "Realistic". This happens at any lat/long of our spheroid. The intensity can be richer due to haze, clouds, smog, etc, but the one thing that is true is if you can see to the horizion and the sun is in the area (even relatively high like 10-15 degrees from horizon) it will cut out most, and at horizon all blue and violet light. That's Earth's atmosphere. So I don't know what "real" atmosphere Terragen's is based on. Sunsets will never be that pale. THAT is a representation of post-processing.

The setting I am talking about is just the vibrancy of the tweak colours being controllable. The strength applied through scattering. This can be controlled just like it is in clouds.

Additionally, the bias to blue is a bit off so you can't create accurate "pink" skies without the ambient sky going green (requiring an additional atmosphere). Though I'm not sure if this can be accurately modeled with 3D programs without normal conditions looking off.

Oshyan

Well, you are quite sure of yourself. And yet... I simply disagree. Vibrant sunsets are generally the exception, not the rule, in my experience. This is probably due to local conditions where I live, in slightly-Northern coastal California. But that's my point really: conditions vary, and you have to pick *some* set of conditions as your defaults. And while it's true that the Terragen atmosphere model does not simulate 100% of atmospheric effects, with the addition of Ozone in Terragen 4 it now handles most things that have a major impact. The default, out-of-the-box look may not be what you want, but you should be able to adjust it to achieve most realistic results.

- Oshyan

pokoy

I don't want to add unnecessary noise to the discussion but since I'm working a lot with real life photography and need TG to produce matching skies/atmospheres I found TG to be pretty realistic out of the box. As Oshyan states, the Ozone parameter has added the last bit of realism, at least for me.

I guess what's missing in the discussion is that converting Wide RGB color space (assuming TG uses a wider space than sRGB internally) to sRGB always comes at the cost of some trade-off and may change how sRGB displays colors, this is especially the case for dark blue / violet / orange / bright yellow tones, blue doesn't seem to be affected much.

Another aspect is that cameras will never work at a neutral white point (6500K for TG I guess) in a natural environment, adding further changes to any image you might be comparing TG's results against. I'm all for an additional Color Temperature parameter in the Frame Buffer as this one could really help to achieve more photo-realistic results.

I'll agree that achieving deep violet sunset colors with TG is a bit difficult without playing with the parameters but Ozone has helped a lot here. With a Color Temperature parameter this could become easier. But the effect is quite a rare occurrence in nature as well and needs some conditions to be met which may be hard or impossible to 'construct' with TG after all.

WAS

June 04, 2018, 01:19:30 pm #7 Last Edit: June 04, 2018, 01:37:16 pm by WASasquatch
Quote from: pokoy on June 04, 2018, 07:52:44 am
I don't want to add unnecessary noise to the discussion but since I'm working a lot with real life photography and need TG to produce matching skies/atmospheres I found TG to be pretty realistic out of the box. As Oshyan states, the Ozone parameter has added the last bit of realism, at least for me.

I guess what's missing in the discussion is that converting Wide RGB color space (assuming TG uses a wider space than sRGB internally) to sRGB always comes at the cost of some trade-off and may change how sRGB displays colors, this is especially the case for dark blue / violet / orange / bright yellow tones, blue doesn't seem to be affected much.

Another aspect is that cameras will never work at a neutral white point (6500K for TG I guess) in a natural environment, adding further changes to any image you might be comparing TG's results against. I'm all for an additional Color Temperature parameter in the Frame Buffer as this one could really help to achieve more photo-realistic results.

I'll agree that achieving deep violet sunset colors with TG is a bit difficult without playing with the parameters but Ozone has helped a lot here. With a Color Temperature parameter this could become easier. But the effect is quite a rare occurrence in nature as well and needs some conditions to be met which may be hard or impossible to 'construct' with TG after all.


I live in the straights of Puget Sound by British Columbia, I watch the sun set in the Pacific Ocean with a unobstructed view of the horizon every night. Clear, cloudy, hazy, overcast, etc. And again, according to basic atmospheric science, at any point you have a unobstructed view of the horizon, and the sun in it, all blue and violet light will be cut out. That means you get oranges/reds/pinks. White is even mix between refractions, just like a prism. TG does already, quite well, but it's falloff is too intense, and close to the horizon.

Additionally, like I was talking about in the asphalt topic, this falloff also effects the sky too dramatically. At 8 degree elevation IRL, the sky here is still pretty much bright blue, and the sun a nice yellow hue cast on objects. However in this image we havea duller (somehow; blues should be deeper and richer not drull) sky, and it's too dark for the elevation. This effects reflections, making things darker than they should be due to darker refractions. Also we get a white bath of mixed colours. So much so the sun is masked by the apposing reds and blues into whites at too far of a corona effect. Even I can look at the sun with the naked eye for a moment and notice a sun, and not so much white washing.

This again why I would like to be able to control the intensity of these decays with a slider. It would be a lot more practical than picking colours, for one, and distorting base colour hues, or spending so much time making sure you're within the same colour hue when selecting a new colour.

I feel at this height, the sun should have more colour at it's source, and more colour on the horizon. It is way to white washed and represents no sunset I have EVER seen, watching them my whole life, or any image in the raw, or edited. Just unrealistic altogether. Sure looks nice, and having been seeing nothing but it working it it all the time, I can see how people are easily bias, or unaware of the subtle differences IRL. 

Additionally, ozone should be "Fake Ozone" as it doesn't work like ozone. If you up it, it doesn't effect the suns corona glow like it would IRL and give you a visible sun disc... like you'd be able to see anyway at this angle in a clear sky. Maybe TGs haze is too strong at default.

Matt

June 04, 2018, 05:24:42 pm #8 Last Edit: June 04, 2018, 05:26:44 pm by Matt
The defaults are a little too hazy for a clear sky, but the added haze looks better once you add clouds IMO, so that influences my choice for the default. Have you tried reducing haze to somewhere between 0 and 0.25, and experimented with small changes to bluesky density (say between 1.5 and 5.0)?

You could also try subtle changes to the colours, but they are quite sensitive.

Matt
Just because milk is white doesn't mean that clouds are made of milk.

WAS

June 04, 2018, 05:31:39 pm #9 Last Edit: June 04, 2018, 05:36:05 pm by WASasquatch
Quote from: Matt on June 04, 2018, 05:24:42 pm
The defaults are a little too hazy for a clear sky, but the added haze looks better once you add clouds IMO, so that influences my choice for the default. Have you tried reducing haze to somewhere between 0 and 0.25, and experimented with small changes to bluesky density (say between 1.5 and 5.0)?

You could also try subtle changes to the colours, but they are quite sensitive.

Matt


That's one of the issues I have been struggling with, when matching sunsets off what I see outside smoking a cigarette, I can't get the blue sky colour to play nice with redsky decay. It's like the bias between colours is too short, or long. Like when doing a reddish-pink sky, your bluesky will be mint or seafoam green, which than requires two atmospheres for proper simulation.


All I'm really asking for is a way to just intensify the decay effect with a slider, so I don't have to fiddle with other settings, or colours. Imagining the class for this feature it seems it works off a basic value or exponential value for it's effect? I don't know. It is a bit of work when you start changing colours getting things accurate, or, staring too long at colours and grow unknowingly bias to your original colour idea from too much exposure to another. Which even impacts your colour perception when viewing the original reference. xD

As is, I can do this by upping the renders contrast a tiny bit, this looks great for atmospheric scenes and distant landscape, and enriches the colours, however, at surface scales, it plays a dramatic role in GI and perceived look of your scene with foliage and such, at least imo. I have very fine tastes. Incredible OCD with art, none of my work is good enough. Not a single one. Lol Not perfect enough.

Also, another edit, this being a settin, would allow it to be animated. From a default atmosphere with high sun, to a rich atmosphere, with super ease.

Matt

June 04, 2018, 05:35:26 pm #10 Last Edit: June 04, 2018, 05:36:58 pm by Matt
Pokoy, it's interesting that you're thinking about wide gamut here, because I've done a lot of thinking about that too.

TG is currently not doing any gamut transform. If you work in sRGB then everything is going to be sRGB. If you display on a wide gamut monitor then it becomes a more complex topic. We could probably achieve more realistic images by simulating in a different colour space. That's a bit of a side project of mine which is currently on the back burner.

Some of those benefits might be possible simply by increasing saturation by 10-20% in post. Maybe...

Matt
Just because milk is white doesn't mean that clouds are made of milk.

WAS

Quote from: Matt on June 04, 2018, 05:35:26 pm
We could probably achieve more realistic images by simulating in a different colour space. That's a bit of a side project of mine which is currently on the back burner.


That honestly sounds like a bit of a undertaking if I'm imagining how TG operates correctly.

Quote from: Matt on June 04, 2018, 05:35:26 pm
Some of those benefits might be possible simply by increasing saturation by 10-20% in post. Maybe...


That's what I usually end up doing, I'll create mask for things that shouldn't be effected, and up vibrancy. Actually usually I'll use curves, and a custom setup per-scene.

Also, I made a lot of edits while juggling my kid entertaining him. Sorry for all the delays in information.

pokoy

Quote from: WASasquatch on June 04, 2018, 01:19:30 pm
This again why I would like to be able to control the intensity of these decays with a slider. It would be a lot more practical than picking colours, for one, and distorting base colour hues, or spending so much time making sure you're within the same colour hue when selecting a new colour.


That's a nice idea, I don't like touching atmosphere colors, slider and some additional parameters would be a good addition.

Quote from: WASasquatch on June 04, 2018, 01:19:30 pm
That's one of the issues I have been struggling with, when matching sunsets off what I see outside smoking a cigarette, I can't get the blue sky colour to play nice with redsky decay. It's like the bias between colours is too short, or long. Like when doing a reddish-pink sky, your bluesky will be mint or seafoam green, which than requires two atmospheres for proper simulation.

I feel at this height, the sun should have more colour at it's source, and more colour on the horizon. It is way to white washed and represents no sunset I have EVER seen, watching them my whole life, or any image in the raw, or edited. Just unrealistic altogether. Sure looks nice, and having been seeing nothing but it working it it all the time, I can see how people are easily bias, or unaware of the subtle differences IRL.


Looking at the image example I see what you mean, the orange haze is too extreme and looks artificial indeed. Similar to your experience, any software that simulates sun at low angles gives me a hard time achieving a believable red/orange tone. For some reason there seems to be a limitation of how precise the simulation can be, and maybe it's due to color space conversion, that's why I mentioned it. Blue sky is never a problem.

Another thing that also plays a role here is tone mapping. I assume TG uses Reinhard but there are a few more modern algorithms that will produce more pleasant (and more photo realistic) images, photographic tonemapping is a good example here. Since tone mapping controls are not exposed we have to live with what we have but it certainly helps to be able to play with tone mapping. (I hope at some point we get more control over image colors and tone mapping right in the VFB.)

And then there's the thing with what the reference would be - a human eye or a camera? Even cameras will produce different color hues depending on brand and model. I guess we have to stick to post production for now, and probably never will be able to get rid of that step.

WAS

It would be really cool to have a tone map and curve map in the filter settings. A lot can be done right in TG with those two features without post work. You can also get them to work nicely with your scene as apposed to a hard pixel manipulation in PS that often causes colour burning and ribbon-ing on gradients.

pokoy

Quote from: WASasquatch on June 05, 2018, 05:48:28 pm
It would be really cool to have a tone map and curve map in the filter settings. A lot can be done right in TG with those two features without post work. You can also get them to work nicely with your scene as apposed to a hard pixel manipulation in PS that often causes colour burning and ribbon-ing on gradients.

Better yet, what if all post production options were moved to the frame buffer, quickly accessible in a sidebar and update immediately upon changes of a parameter without the need to rerender? That's a feature I'd love to see, just like a lot of renderers do it already.