CORONA SUN+ SKY VS HIGH QUALITY HDRI

[Romas Noreika]

Hello there,

this thing that I have to get off my chest.

The purpose of using a HQ HDRI versus just corona sun+SKY.

WHY?

I did some tests simple scene nothing special just to see how the lighting works and the shadows are behaving.

I did put a high quality HDRI from www.hdri-skies.com and mediterraneanlight.

the thing is I was able re-create that effect and that lighting of a specific HDRi with just corona sky and sun controlling them together almost 95% accurate.

Which I have never was capable to do with VRAY sun and sky. Vray sun and sky works a lot different than corona sun and sky. Its just not the same thing.

So I am in a cross road now. I can use Corona sun +sky for the lighting and I can put whatever HDRi map in the reflection, refraction, direct visible slot. For nice reflections.

+with sun+sky you have a lot more control regarding animations sunrise - sunset and so on.

Anyways - I would like to know what is your opinion on this one regarding ONLY CORONA sun+SKY VS HDRI.

Because corona sun+SKY is a very good quality HDRI alike replica. With very nice easy controls.

I am just curious what other people think or have to say from their own experience.

[maru]

First of all, you cannot get some weather conditions with Corona sun+sky only, for example setting sun behind clouds. Second thing is that a HDRI will affect the scene in a different way - the lighting will be also bounced off trees, ground, or whatever there is in the HDRI.
To mess with your head even more, you can also use Sun+Sky together with an HDRI. :)
https://forum.corona-renderer.com/index.php?topic=17008.0

[Juraj]

Each has its own set of benefits&drawbacks, that become more evident in different type of imagery.

Vray Sun&Sky can produce absolutely the same result that Corona, but you have to use the same 'model' that Corona uses (Hasek). Vray also feature Preetham and CIE models that are not as good.

Benefits of Sun&Sky:
+Super flexible in use, vertical/horizontal angle, temperature (for both direct&indirect), direct&indirect light ratio adjustment.
Drawbacks:
-Current model can't do night time & blue hour at all, and extreme sunset isn't as very convincing.
-Can't do complex lighting that would result in interesting shadow penumbra ( Sun hid behind clouds gets larger and softer in non proportional way)
-Can't offer complex and believable reflections alone.

Benefits of HDRi (Alone):
+IF DONE RIGHT (90 perc. of HDRis on market are not correct or realistic at all, even the most popular), provides exact replica of real-world lighting in its full complexity.
+Every light situation posssible in real world, is possible to capture in HDRi (but some situation are very hard to capture, and again, 90perc. wrong in HDRis you can get or buy).
+Can provide reflections, which is super necessary for product&automotive visualization, can provide background visuals without use of backplates (but can work together)
Drawbacks:
- 95perc. of HDRi are wrong. They lack dynamic range ( Sun needs up to 16.5 dynamic stops alone ), are color corrected ( HDRi cannot be color-corrected, no white balance or contrast adjustments) so they can provide nice&interesting light, but don't resemble the real-light.
- Unflexible. Can't change vertical angle (well technically you can if you separate direct light source, but this is not how 99perc. of HDRis on market are setup).
- Unflexible. Can't change light type of direct light unless it was properly separated (which most are not, they are just clipped, but not separated).

Benefits of HDRi + Direct light (or Sun):
+ Can provide flexibility of direct light with complexity of light&reflections from HDRi.
- Only looks good when direct light was separated (literally painted away) so it doesn't provide any light intensity, not just clipped intensity.
(The old workflow with clipped HDRi + Sun is creates two shadows unless it's perfectly aligned. It's mostly not visible, but it's just not proper way and solution is quite easy).

Lot of people wrongly believe HDRi provide magical light that can't be created otherwise all the time :- ) These people also probably believe in Santa-Claus as well.
But for product & automotive visualization, HDRis are everything. For interior archviz ? Not so much.

[rambambulli]

These people also probably believe in Santa-Claus as well.

OH NO!. He doesn't' exist?

95perc. of HDRi are wrong. They lack dynamic range ( Sun needs up to 16.5 dynamic stops alone ), are color corrected ( HDRi cannot be color-corrected, no white balance or contrast adjustments) so they can provide nice&interesting light, but don't resemble the real-light.

Do you know which skies are correct?

What skies do you prefer in your workflow?

[romullus]

These people also probably believe in Santa-Claus as well.

OH NO!. He doesn't' exist?

Of course he does. There's no reason to stop believing, just because some random guy on the internet told you so. Now, be a good boy - it's only few months till Christmas :]

[Romas Noreika]

Thank you Maru and Juraj for the explanation :) Its very helpful :)))

I think now that whatever looks realistic and provides you the result that you want  - so use it. Even if its just SUN +SKY. Or just hdri alone.

Anyways thank you again for the reply :)

[maru]

Yup, basically once you are aware of the pros and cons, you can pick the one you need in a specific case, or mix them if needed.

[matsu]

I always remove the sun from my HDRis and use Corona sun. Pretty flexible, and best quality. Photoshopping out the sun only takes like 10 minutes anyway...

[Juraj]

I always remove the sun from my HDRis and use Corona sun. Pretty flexible, and best quality. Photoshopping out the sun only takes like 10 minutes anyway...

Unless the person used f22 and shot of-sun direction. Massive flare across half the hdri :- D

Nice to know someone does it !

[Romas Noreika]

I always remove the sun from my HDRis and use Corona sun. Pretty flexible, and best quality. Photoshopping out the sun only takes like 10 minutes anyway...

That's a pretty cool idea. Never heard about it :) Thank you will try it out.

[Romas Noreika]

[/quote]

Unless the person used f22 and shot of-sun direction. Massive flare across half the hdri :- D

Nice to know someone does it !
[/quote]

Juraj could you please explain what did you mean by that?

[RolandB]

I always remove the sun from my HDRis and use Corona sun. Pretty flexible, and best quality. Photoshopping out the sun only takes like 10 minutes anyway...

Very good idea ! Why not think of it before? Thanks !