Author Topic: Cloud Days and Terragen Sun  (Read 459 times)

Offline WASasquatch

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Cloud Days and Terragen Sun
« on: November 15, 2018, 07:08:41 PM »
What's the secret to nice illuminated clouds, that don't let the sun burn through (creating a bright spot) but also provide ambient light for terrain?

I've always had issues balancing this. It seems Terragen's sun object likes to really pierce clouds, even with disc disabled. When I can get the sun to not show through the clouds, they're also too dark for any definition, and the ground is near blackness.

Overcast, not even full Cloudy Days, do amazing jobs hiding the suns location altogether while illuminating the surface. Take the Vikings and the need to create the "Sun Stone" to find the sun with overcast and clouds -- and other civilizations straight blind to navigation during these sort of conditions.
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Offline Rich2

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Re: Cloud Days and Terragen Sun
« Reply #1 on: November 15, 2018, 07:40:09 PM »
I'm not sure about Terragen's sun.  I tried to create an eclipse scene and the sun shines right through the planet in the sky.  I've set the sun behind a mountain and it shines through.  So why would clouds make a difference?
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Offline WASasquatch

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Re: Cloud Days and Terragen Sun
« Reply #2 on: November 15, 2018, 07:42:45 PM »
I'm not sure about Terragen's sun.  I tried to create an eclipse scene and the sun shines right through the planet in the sky.  I've set the sun behind a mountain and it shines through.  So why would clouds make a difference?

That's due to your render settings and the sun disc.

This is sort of related to the same issue with a Light Source being at moon-distances from the planet, but the center of the omni-directional glow creating a focus point in the planets atmosphere, rather than naturally cascading onto the atmosphere with more uniform intensity.
« Last Edit: November 15, 2018, 07:44:30 PM by WASasquatch »
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Offline WASasquatch

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Re: Cloud Days and Terragen Sun
« Reply #3 on: November 15, 2018, 08:27:02 PM »
Here is an example of the sun blasting through thick clouds. Imo this effect, to conform to clouds of this thickness IRL, that sun effect should be muuuuch larger until the sun location is pretty much indistinguishable.

Already these clouds are darker than they should be, due to having to increase density to fight the sun, but the sun still pierces through waaaaay more than it should.
« Last Edit: November 15, 2018, 08:29:46 PM by WASasquatch »
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Offline Dune

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Re: Cloud Days and Terragen Sun
« Reply #4 on: November 16, 2018, 04:35:57 AM »
Maybe with overcast skies you need to decrease sun strength and increase GI and exposure.

Offline bobbystahr

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Re: Cloud Days and Terragen Sun
« Reply #5 on: November 17, 2018, 11:32:17 PM »
Jordan, I had a stab at this a while back and I got this far. I've included the .tgd as well so look at all parts cause I tweaked mindlessly to get this far
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Offline the first seer

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Re: Cloud Days and Terragen Sun
« Reply #6 on: November 18, 2018, 03:26:55 PM »
Very interesting topic, that concerns me a lot!
Have a few times a picture as original renderer with sun and clouds made, then a 2nd Render without sun as a section and it in PS as a masked layer fades as I liked.

Offline bobbystahr

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Re: Cloud Days and Terragen Sun
« Reply #7 on: November 18, 2018, 03:40:35 PM »
Very interesting topic, that concerns me a lot!
Have a few times a picture as original renderer with sun and clouds made, then a 2nd Render without sun as a section and it in PS as a masked layer fades as I liked.

I prefer to do atmospheric stuff within TG but I agree it's a good cheater.
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Offline the first seer

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Re: Cloud Days and Terragen Sun
« Reply #8 on: November 19, 2018, 09:34:10 AM »
You are also a master in TG my friend!

Beautiful picture, thank you for sharing :)

Online cyphyr

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Re: Cloud Days and Terragen Sun
« Reply #9 on: November 19, 2018, 09:52:56 AM »
Think of it in terms of a camera.
On cloudy days you would have to turn use a wider aperture and/or longer exposure.
Whilst aperture can be controlled it only effects DOF so we have to use exposure instead.
This can be modified via either the camera node or the vertical slider to the left of the preview window.
Works in PBR mode but you'll get a more accurate result in normal preview mode.
Good luck :)


Hmm well it should work ... I have just done some tests and I'm getting some weird bright fringingat surface boundaries (land>sky, object>sky)
Verry odd.

Yeah It works :)
I had pushed the background colour up to a light grey
« Last Edit: November 19, 2018, 10:59:19 AM by cyphyr »
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Offline the first seer

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Re: Cloud Days and Terragen Sun
« Reply #10 on: November 19, 2018, 02:58:18 PM »
Think of it in terms of a camera.
On cloudy days you would have to turn use a wider aperture and/or longer exposure.
Whilst aperture can be controlled it only effects DOF so we have to use exposure instead.
This can be modified via either the camera node or the vertical slider to the left of the preview window.
Works in PBR mode but you'll get a more accurate result in normal preview mode.
Good luck :)


Hmm well it should work ... I have just done some tests and I'm getting some weird bright fringingat surface boundaries (land>sky, object>sky)
Verry odd.

Yeah It works :)
I had pushed the background colour up to a light grey

Why is this crossed out and what about grey, this really works?
« Last Edit: November 19, 2018, 03:13:02 PM by the first seer »

Online cyphyr

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Re: Cloud Days and Terragen Sun
« Reply #11 on: November 19, 2018, 04:14:36 PM »
Sometimes for an overcast scene but without clouds you can raise the background colour to grey or white and it gives a less contrasty look to the scene. In this case I had also boosted the exposure which made the scene readable but with the ligt grey background gave a weird bright speckled line where the models and mountains overlapped the sky.

SO a solution to your overcast issue may be to not so much work with the sun, cloud and atmosphere but to work with the camera and exposure.
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Offline the first seer

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Re: Cloud Days and Terragen Sun
« Reply #12 on: November 20, 2018, 07:54:43 AM »
Thanks for the tip! :)

Offline René

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Re: Cloud Days and Terragen Sun
« Reply #13 on: November 20, 2018, 12:34:42 PM »
The sun shining through the clouds is partly due to sun glow amount and power. You can set those values lower or switch them off completely. Probably you will need stronger GI surface details to compensate for the lack of contrast.

Offline bobbystahr

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Re: Cloud Days and Terragen Sun
« Reply #14 on: November 20, 2018, 01:01:24 PM »
The sun shining through the clouds is partly due to sun glow amount and power. You can set those values lower or switch them off completely. Probably you will need stronger GI surface details to compensate for the lack of contrast.

D'oh...of course...well worked out Rene

Just tried that setup with ver 1 clouds and it works well with those clouds as well but on this old DELL a fair bit faster.
« Last Edit: November 20, 2018, 01:42:10 PM by bobbystahr »
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