The Sun (no not the newspaper)

[Oshyan]

Actually the sun itself in real life would appear as a virtually perfect disc without the atmosphere, so it is in fact the atmosphere that you want to look to for these effects. Looking at the Vue image I'd actually say that it looks decidedly *unrealistic* compared to the real world, except in very specific circumstances. Normally, if you can see the sun that clearly (i.e. there's not significant glow around it virtually hiding its outline), then it is pretty sharp. The only time you might see something like the Vue image is in fog or a sand storm. But feel free to find photo reference to prove me wrong.

In any case the "Glow in atmosphere" setting accomplishes at least part of what you're looking for, I think - try turning it off and your results get worse. Ok, that's not quite what you want, to make things worse. However, see if turning off Visible Disc is more to your liking...

Even if that does improve things for you, I would agree that the sun rendering is not ideal. Again I would *not* say Vue's is particularly superior (although I grant many people may *think* the sun looks like that), but there are certainly things that could be handled better in TG2 in regards to the sun. A proper "glow" function for bright surfaces would help a lot. The simplicity of the "visible disc" function is probably to blame for a lot of the realism issues in this case.

- Oshyan

[reck]

I don't know Oshyan, I think the sun at lower altitudes should have more of a glow and brightness about it, or at least the option to do this. Taking a quick look at some pics via google most of the sunset images don't have such a well defined disc shape about them.

On the other hand there were a few images that did look more like the terragen sun such as the last pic, but the vast majority are more like the first ones. Obviously it depends on the atmospheric conditions at the time, maybe more controls could be added to the sun to try and emulate the first set of pics?

I tried turning off the visible disc but in my opinion it doesn't look good. I shall take another look at the "glow in atmosphere" setting but I have a feeling it would affect the whole look of the sky rather than just the sun. Sometimes you get a great scene setup with lighting and colours just as you want, but you want to make the sun have more brightness and glow without affecting the rest of the scene.

[rcallicotte]

To be fair, though, the photos aren't going to be like a realistic view.  Film or digital medium skews the light rays of the sun.

Taking a quick look at some pics via google most of the sunset images don't have such a well defined disc shape about them.

[reck]

That's true. But even in real life when you see a sunset with your own eyes it tends to look more like a glowing sphere than a luminous white disc, maybe not all the time but sometimes (most of the time?) it does.

[rcallicotte]

I especially agree with that when it's sitting over the ocean...due to atmospherics.  Too true.

[Oshyan]

The first reference image you provided looks like neither the TG2 image nor the Vue image - I think that's about how it looks if you turn off visible disc, or if you just have a high brightness/glow. The 2nd image looks closer to the TG2 than Vue. I do agree that more control is needed for the sun and the sun disc effect in particular is too simplistic, as I noted before, but I don't think Vue necessarily has the more realistic solution right now, regardless.

- Oshyan

[Mohawk20]

I did some space renders, and in those the sun looks extremely 'disky'. There the glow would not be caused by the atmosphere, but more by how our eyes react to the brightness, and how it shines through the hairs around our eyes.

Anyways, the brightness of the sun has a lot to do with the glow, and you can't always recognize that it's that bright in a render, until you start saving them as exr files and go play with tonemapping software. Then the brightness of the sun starts to affect the surrounding pixels more like you'd expect.

[Cyber-Angel]

In nature (Not sure about TG2) the sky its self is a source of illumination due to "Diffuse Sky Radiation"  more about which can be found on this Wikipedia article http://en.wikipedia.org/wiki/Diffuse_sky_radiation and time permitting in future the lighting model of TG2 should consider this if it dose not already.

Regards to you.

Cyber-Angel   

[latego]

The worst problem of the TG render is the the sun, even though it is just above the horizon, is still a perfect circle. Just have a look at http://www.tripadvisor.it/LocationPhotos-g608952-Peniche_Estremadura.html#17467154 or http://www.chocolate-fish.net/img_-3777_lang_italian.

Another problem of the TG render (obviously related to the above one) is that the color of the sun disk is the same everywhere. The Peniche image shows well that in realistic conditions the lower part (having its light go thru a large air volume) is markedly redder than the upper part. This effect can be masked by postprocessing or appropriate exposure (as demonstrated by the Brighton Pier image, but this is a photographer decision, not the accurate atmospheric behaviour.

Just to give an example of the obscene complexity of the problem, have a look at http://www.pbase.com/warthog2100/image/52579824. There you will find an animation made by several photographies, showing the sunset phenomenas, including the very elusive Green Flash (no, rest assured, Vue does not green flashes, nor does any GC program I know of ).

There are situations in which the photographies show almost exaclty the Vue render situation: e.g. see http://www.yepayepa.net/kl18th/wp-content/uploads/Sunset%20Boracay.jpg or http://www.travelblog.org/Wallpaper/sunset_wallpaper_brazil.html (scroll to the bottom of the page for the actual wallpaper).

The problem in general is that there is an atrocious difference of illumination between the sun disk and the rest of the scene so exposition time and even slight differences of atmosphere transparency, haze, turbolency, water vapor etc. can make great difference in the final image.

At least, TG should handle the different light path air thickness w.r.t. height above the horizon. This should almost automatically provide sun disk squashing and lower limb reddening.

Bye!!!

[Mohawk20]

Another problem of the TG render (obviously related to the above one) is that the color of the sun disk is the same everywhere. The Peniche image shows well that in realistic conditions the lower part (having its light go thru a large air volume) is markedly redder than the upper part. This effect can be masked by postprocessing or appropriate exposure (as demonstrated by the Brighton Pier image, but this is a photographer decision, not the accurate atmospheric behaviour.

Just to give an example of the obscene complexity of the problem, have a look at http://www.pbase.com/warthog2100/image/52579824. There you will find an animation made by several photographies, showing the sunset phenomenas, including the very elusive Green Flash (no, rest assured, Vue does not green flashes, nor does any GC program I know of ).

The problem in general is that there is an atrocious difference of illumination between the sun disk and the rest of the scene so exposition time and even slight differences of atmosphere transparency, haze, turbolency, water vapor etc. can make great difference in the final image.

At least, TG should handle the different light path air thickness w.r.t. height above the horizon. This should almost automatically provide sun disk squashing and lower limb reddening.

Bye!!!

I must disagree on the point of colour! I've attached a few of my renders which do show clear discolouration with the right atmo settings.

[reck]

Latego that's very interesting. It just goes to show how many different ways the sun can look depending on certain conditions.

After spending some time looking at this I now think that the TG sun is not as bad as I first thought. It is possible in some situations for the sun in real life to look like the TG sun, but only in some situations. I hope in the future to have more parameters to play with for the sun to simulates the other images of sunsets we've seen.

I have to agree with Mohawk, when I was playing around last night with sunsets the disk does change colour towards the bottom of the disk. Most of the sun was white and then the last 10% had a red/orange tinge to it.

[moodflow]

I just now read this thread and wanted to add a few things, until I saw Mohawk's post.  I agree with him and his renders show what can be achieved in TG2.  You can get that gradiated color sun effect, just by playing with the atmosphere.  Yes, it can change the scene somewhat, but thats likely what would happen in real life anyway.

One thing I think TG2 should eventually simulate, is the atmospheric refraction that distorts the shape of things near the horizon - ie, how the sun becomes more "oval" at the bottom when its close to the horizon.

[rcallicotte]

Atmospheric Refraction?     Yah.

[moodflow]

Atmospheric Refraction?     Yah.

It was my tone of voice, wasn't it.   

[rcallicotte]

Uh huh.