Can V-ray emulate Corona reflections?

[emianemi]

(Please click on links above images if the entire image is not shown)

Hello everyone, I'm a Corona user, i fiddled a little with V-ray but never really used it.

I was given a task of changing several assets from Corona to V-ray, being a Metal ray user (before Corona) I thought it will be a fairly simple task since material creation in those two is quite similar. But, I can't seem to get anywhere near Coronas results.

 

I hope someone here knows both Corona and V-ray, but in short Corona uses PBR materials and for reflection tweaking you just leave reflection value at one, IOR at ~1.6, and just tweak glossiness value (for 95% of materials).

 

So first I tried doing the same thing as in Corona, changing just glossiness value:

 

http://i.imgur.com/ckW7h96.jpg

 

 

As you can see, this got me nowhere.

 

Then I tried changing the reflection values as well, since that is "the old way", just like it was in Corona before PBR and as it is in Mental ray, balancing glossiness, IOR and reflections values.

 

But, that also didn't work. While Corona at glossiness 0.5 gets blurred but defined reflections, V-ray just creates one big blur.

 

http://i.imgur.com/nJXtwFP.jpg

 

 

Then I tried with a map, in Corona plugged just in glossiness, in V-ray first only reflections, then only glossiness, then both. Again, no go.

 

http://i.imgur.com/h2vhyEo.jpg

 

 

 

Tried the same thing again but run the map through Mix map to accentuate the problem

 

http://i.imgur.com/h3z2hK6.jpg

 

[emianemi]

Things get even worse when i drop down IOR to a more realistic value (still higher then needed for wood to have clear reflections). Corona is pretty straight forward, "raised" parts of wood are reflective, "lowered" ones are not.

V-ray, uniform washed out reflections.

 

http://i.imgur.com/1dskwG2.jpg

 

 

 

 

I also tried plugging the diffuse map into reflection (not Mix map as above), but that just changed reflections a bit, not solving the problem.

 

http://i.imgur.com/OBC45yS.jpg

 

[Nicolai Bongard]

Have you tried playing around with different BRDF`s?

[Devin Johnston]

Very interesting, maybe that's why Chaos bought them!

[RyderSK]

Have you tried playing around with different BRDF`s?

 

This should be the correct answer.

 

To get matching behaviour, you need the latest Vray, and BRDF set to GGX and Glossy Fresnel. Not sure which one they use as the default currently, but probably still Blinn+Legacy Fresnel.

Edited September 12, 2017 by RyderSK
small naming mistake

[emianemi]

Have you tried playing around with different BRDF`s?

 

 

Yea, I was able to get somewhat close by balancing reflection, glossiness, IOR and changing BRDF model. I wouldn't exactly call it "close", but hey...

The thing is, I have quite a few of these materials to convert. I was hoping there would be some "formula", if in Corona glossiness is X, in Vray set reflection and glossiness to Y and Z. "Manual" conversion will take some time and lot's of re-rendering. Looks like there's no shortcut.

[Dejan Sparovec]

This should be the correct answer.

 

To get matching behaviour, you need the latest Vray, and BRDF set to GGX and Rough Fresnel. Not sure which one they use as the default currently, but probably still Blinn+Legacy Fresnel.

 

Sorry for going a bit off topic, but what is Rough Fresnel?

Do you mean selecting "Use roughness" in BRDF options? I have no idea how to use that workflow, any links that could explain this?

Thanks!

[RyderSK]

Sorry for going a bit off topic, but what is Rough Fresnel?

Do you mean selecting "Use roughness" in BRDF options? I have no idea how to use that workflow, any links that could explain this?

Thanks!

 

Definitely not off-topic :- ).

 

I made a mistake, they called it "Glossy Fresnel". In this link they explain it themselves https://labs.chaosgroup.com/index.php/rendering-rd/understanding-glossy-fresnel/

 

Use Roughness only inverts the numbers for Glossiness because Roughness is more common these days (it's also much better, logical name).

[Dejan Sparovec]

Oh right, I forgot about glossy fresnel

There's a checkbox for it under Options in the material editor. Should be on by default, though.