Author Topic: Why does Corona Sky horizon look so bad?  (Read 1872 times)

2022-03-21, 14:17:06

ShynnSup

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I mean, I always get this diffused white at the horizon, and I have no control over it. For starters it does not work ok out of the box.

This is the result out of the box: Horizon on new planet, perfect gray line.



Change altitude you say: (2500m)



Does this look any better to you? The white diffuse gradient at horizon is not natural,  and if you have a water material it totally messes it up by making it also too white!
Same image as before with alpha:


Does that look like a normal water color at horizon to you?

Please guys, just look at some real photographs. Or at least give us some control. Right now I can't change the color nor can I reduce the gradient, only increase it....

Look at this horizon:


Look at this horizon:


Look at this horizon, look at the color of the water. No white!



Thank you

2022-03-21, 14:32:05
Reply #1

hurrycat

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I have been struggling with this as well, although in 3ds Max, but I would guess it's the same. In most cases I have been able to reproduce the reference I am after. Sometimes the horizon in real life is very close to what CoronaSky gives.

Oher times I have had success by increasing the altitude (not rarely at its Max limit of 15000m) and also changing the Intensity. You can also ColorCorrect the CoronaSky map (for example give it a cooler temperature >6500K, to give it a unified blue tint), and maybe feed it to the Direct Override Slot, so that it does not interfere with the lighting of your scene.

Lastly, you can feed it through a CoronaTonemapControl, so that it stays consistent while changing the Exposure.

What I'm basically saying is that you can get the result you want, but usually through tweaking the Sky map. So yeah, I agree that extra options for the Sky model would be great, but I'm not sure where I would begin with that. Maybe we will see this in Corona 9, along with a fix for the problem with using Environment Overrides and Volume effect at the same time. Cheers!

2022-03-21, 14:43:33
Reply #2

ShynnSup

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Thank you for the workaround suggestions...

I must be missing something because I can't find the CoronaSky map here in C4D in order to color correct it or apply the CoronaTonemapControl. I can only do this with HDRIs.

2022-03-21, 14:50:20
Reply #3

BigAl3D

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That Corona water example you posted and asked "Does that look like a normal water color at horizon to you?" actually, it does match the sky you have. It is reflecting the lighter colored haze at the horizon in your example. I think one thing you may not be considering is the clarity and depth of the water, plus is it sand or seaweed growning on the bottom. In those pics that show the water darker at the horizon, that is indicating a drop-off in water depth which usually looks darker. The placement of the sun also affects the look of the water.

I'm not totally disagreeing with your issue, but there is more going on in Mother Nature that we as 3D artists add to our scenes. Like Hurrycat indicates, you are still an artist and need to add your own touches to the results. Just my two cents.

2022-03-21, 15:02:29
Reply #4

ShynnSup

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Read carefully. I never said the water material is not working ok. I said the horizon of the sky is not natural. Of course the water is going to reflect the sky just fine and, in this case, amplify the horizon error.

The water is looking unnatural not because of the sun or because of a missing surface underneath it, but because of the sky horizon not being ok. Clearly the problem is not the water, the sky is.

Also, how am I suppose to 'add my own touches' to the results when there are no controls for it? The suggestions hurrycat recommended are not possible in C4D if I am not mistaken...

2022-03-21, 15:06:17
Reply #5

TomG

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All of hurrycat's suggestions work fine in C4D. Other suggestions on adjusting the look - the fake horizon blur parameter; the aerial perspective (volume effect); changing the ground color; overriding direct visibility, reflections, etc. as necessary so that you see/water reflects something that matches what you want but the lighting can come from the sun and sky.
Tom Grimes | chaos-corona.com
Product Marketing Manager | contact us

2022-03-21, 15:07:00
Reply #6

davetwo

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I had a project a year or so which had a some mountains and a big lake. I thought I knew how it should look - and the software gave me an image that I expected (intense reflection at the far edge).

The real life photos the client sent back made me re-evaluate this. In many cases the strong reflected colour simply wasnt there.

The real-world water seemed to be breaking up the strong fresnel effect with a combination of absorbtion and the 'choppiness' scattering the light.

I think none of us are modelling at real world scales/depths for the lakes and oceans. So I'm not sure how 'incorrect' Corona is. Or if out models are naturally too simplistic to replicate these real-world effects.

It's not a problem with Corona's sky model IMHO.



2022-03-21, 15:17:04
Reply #7

ShynnSup

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@TomG

Fake horizon blur parameter only amplifies the problem.
Volume effect does nothing to solve this.
Ground color as well does not help the issue (and affects the whole scene illumination)
Overriding visibility means using another image as a background which defeats the purpose.

Where can I color correct the CoronaSkyMap?

Thanks

2022-03-21, 15:27:14
Reply #8

TomG

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My method for that is to swap the sky object to Shader mode, then choose a Color Correct, and then in that choose the Sky shader. A quick test just now found that tinting and raising the gamma worked well for adjusting how bright (or not) the horizon is, but the Color Correct can do loads of things so adjust to taste and needs!
Tom Grimes | chaos-corona.com
Product Marketing Manager | contact us

2022-05-19, 05:36:47
Reply #9

ShynnSup

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Hi guys, sorry to bump this thread but I ran into this issue again today, I simply had to Photoshop the background with a sky photograph.

I tried the suggestions given to no avail. I keep struggling to just change the horizon without affecting the entire sky shader. Tried gradients and layer shader with another gradient as a mask, which honestly felt like a very long shot for something that should be very simple:

We basically need the 'Fake Horizon Blur' parameter to go negative, in order to decrease the blurring at the horizon, making it possible to have an almost plain blue horizon, with no white gradient.

« Last Edit: 2022-05-19, 05:45:38 by ShynnSup »

2022-05-19, 15:03:53
Reply #10

BardhylM

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I do not think the problem is with the sky, it is more of a water material problem (struggled myself too).
You can see in your examples the sea is darker than the sky, as in you will have haze in the sky closer to the horizon, but not in the sea(except in extreme cases).
As BigAl3D mentioned that it may be the case that in that scale sea does not have the "glossiness" of a close up water, but is far rougher and it does not have regular sheen.
Not an expert but probably the waves that far turn the surface matt just as micro surface bump affects normal objects.

TLDR For oceans and sea water, the further from us seem like do not reflect and therefore darker. You can somehow fake it with the legacy material in the Reflections with a Fallof map choosing Towards/Away option.

2022-05-19, 19:13:48
Reply #11

burnin

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yes, here's another phenomena, sort of reversed micro-roughness - as you can observe IRL and photographs, fresnel on horizon isn't present, while in shorter distance reflection from water surface is stronger (appears normal), my thinking is, because farther from coast surface gets rougher, more dispersed, w/ higher waves culminate to matte/diffuse appearance  overrides smooth surface fresnel ...     

2022-05-19, 21:06:48
Reply #12

ShynnSup

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Guys, forget the water please! This is not about the water. The same problem happens when you have any other material as ground surface. The problem is the sky graduates from sky color to white, and there is no way to control that gradient, at least not without affecting the illumination of the whole scene.

2022-05-20, 03:22:40
Reply #13

burnin

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'tis tinted PRG Sky

2022-05-22, 22:25:09
Reply #14

Stefan-L

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or just use height 25m ( to solve the grey line in very very first image), for me that solves the grey line you get with 0m altitude.

overall if you need a custom sky solution (the build in never can give all possible solutions) why not use a bitmap image as BG.
this works great, i also use that here and there a,d you can perfectly fine tume it to your needs?