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Is the sun supposed to look like this?
http://sldev.free.fr/forum/viewtopic.php?f=6&t=2279		 Page 1 of 1
Author:  linyifei [ 2022-06-06 13:14:06 ]
Post subject:  Is the sun supposed to look like this?
I recently updated to Cool VL Viewer 1.30.0.0 and was a bit startled to see the sun looking like this:
Image
Is it supposed to look like that, or is there something wrong?
Author:  Henri Beauchamp [ 2022-06-06 14:12:27 ]
Post subject:  Re: Is the sun supposed to look like this?
And what is "wrong", please ?
Author:  kathrine [ 2022-06-06 20:41:41 ]
Post subject:  Re: Is the sun supposed to look like this?
I would guess the aurora in yellow and orange should be centered around the round white disk and not float higher over the horizon?
Author:  ZaneZimer [ 2022-06-06 21:36:34 ]
Post subject:  Re: Is the sun supposed to look like this?
It has been like this in EE for as long as I can remember. I think it's to mimic 'lens flare' or other atmospheric phenomenon. The Linden viewer doesn't do it because, as Henri noted in another thread, it just 'disappears' the sun disc into the fog at the horizon. See this real world photo, to see the affect there: Dundee Beach.
Author:  Henri Beauchamp [ 2022-06-06 23:29:53 ]
Post subject:  Re: Is the sun supposed to look like this?
ZaneZimer wrote:
It has been like this in EE for as long as I can remember. I think it's to mimic 'lens flare' or other atmospheric phenomenon. The Linden viewer doesn't do it because, as Henri noted in another thread, it just 'disappears' the sun disc into the fog at the horizon. See this real world photo, to see the affect there: Dundee Beach.
+1

I won't have explained it better (this effect is however not the result of lens flare or any optical defect/artifact, but simply how the refraction works in the atmosphere near the horizon)... Thank you.

And yes, if you compare with the old WL renderer, it is definitely more realistic now in the EE renderer...
Author:  linyifei [ 2022-06-07 00:24:56 ]
Post subject:  Re: Is the sun supposed to look like this?
Henri Beauchamp wrote:
And what is "wrong", please ?
Well... Perhaps "wrong" was the wrong word, but the huge hard-edged white disk sun (complete with sunspots?) looks peculiar to me, more like the moon than the sun, and the way it doesn't line up with the bright patch in clouds between the sun and the viewpoint is a bit strange.
However, I gather from the comments above that it is working as designed, and I just have to get used to it. Thank you everyone for your replies.
Author:  ZaneZimer [ 2022-06-07 02:19:56 ]
Post subject:  Re: Is the sun supposed to look like this?
Henri Beauchamp wrote:
..., but simply how the refraction works in the atmosphere near the horizon
I did a bit more reading, because I have always been curious about the real world effect. An explanation says it seems to be caused by ice crystals reflecting the sunlight, creating a more diffuse, 'extra' image above the apparent position of the sun. It's cool that the EE renderer recreates this in a virtual way.
Author:  Henri Beauchamp [ 2022-06-07 08:53:25 ]
Post subject:  Re: Is the sun supposed to look like this?
linyifei wrote:
Henri Beauchamp wrote:
And what is "wrong", please ?
Well... Perhaps "wrong" was the wrong word, but the huge hard-edged white disk sun (complete with sunspots?) looks peculiar to me, more like the moon than the sun, and the way it doesn't line up with the bright patch in clouds between the sun and the viewpoint is a bit strange.
While a bit more accurate than what was seen in WL, EE is of course not 100% realistic, by far ! Note that there were even more parameters (and thus a better accuracy) in early (pre-release) EE versions (see llrender/llatmosphere.* in LL's viewer sources), but these got deactivated ('gAtmosphere' stays always NULL in LL's viewer, so I simply got rid of the corresponding unused sources in mine), probably because it caused too large a slow down in the FPS rate...

As for the Sun disc diameter, it happens to be (almost) equal to the Moon's in RL (which gives us full Sun eclipses, sometimes), so the Sun disc is in no way "huge" in the EE renderer, but it was unrealistically small in WL and, in fact, the Sun disc was never properly rendered "near" (for elevations 45° or below) the horizon (it was also sensitive to the "WL sky details" setting, with huge distortions at low setting value, which is no more the case).
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