New Energy conservation mode

[romullus]

Tried to create snow material today and found that legacy mode gives much superior results in that case. What a shame, i really like GGX BRDF and wouldn't want to revert even for single material :] Looking forward to what solution dev team will offer.

[Ludvik Koutny]

Yep, snow is extreme case of this problem. It's very rough, yet highly reflective, also refractive, has SSS and is white. So as long as the problem is present, it's not possible to make good looking snow with GGX.

[Juraj]

Just found this error in my scenes too. I guess I was oblivious to it as most rough materials were dark and I didn't notice it so straight up. I still use white wall to be mostly diffuse since the roughness is so high.

Well, touche :/

[daniel.reutersward]

This problems explains a lot of why I had problems with some materials...

A little off topic, but a little bit on the subject: How come Corona GGX don´t have any more advanced controls for tail fall off etc? Just curious :)

[Juraj]

Because the GGX by default doesn't seem to have it. The one that has the control, is for example the version Vray incorporated (GTR/GGX).

[daniel.reutersward]

I see, so it´s a different GGX model? That explains it!

[Juraj]

The Disney paper describes few models: https://disney-animation.s3.amazonaws.com/library/s2012_pbs_disney_brdf_notes_v2.pdf

Walter - No Tail parameter
Low; Bagher - Tail parameter
Trowbridge & Reitz - GTR; [Gamma=2]  = GGX ; The one in Vray

No idea which we got in Corona, perhaps the parameter simply isn't exposed.

[daniel.reutersward]

Thanks! I will take a look at the paper, interesting! :)

[vkiuru]

Oh, so this is what was happening with some of my materials. Spent some time tweaking them and wondering what I'm doing wrong, kinda happy to see it wasn't me.. hoping for a fix, though - other than switching to legacy.

[snakebox]

Correct or not, it does less damage than black outlines. You can't just tell client "Sorry, our renderer can't render that bulb without those ugly black edges". Hopefully others will help me convince you it simply can't stay this way, if Corona's ever supposed to be production renderer.

This! sometimes the option to break reality HAS to be there, production doesn't follow realistic time frames always so people need an option to achieve unrealistic results.

[Ludvik Koutny]

Correct or not, it does less damage than black outlines. You can't just tell client "Sorry, our renderer can't render that bulb without those ugly black edges". Hopefully others will help me convince you it simply can't stay this way, if Corona's ever supposed to be production renderer.

This! sometimes the option to break reality HAS to be there, production doesn't follow realistic time frames always so people need an option to achieve unrealistic results.

Nope, this is not anyhow related to speed or realism. It's simply broken shading model. Meaning that if you took a photograph of white rough reflective Christmas bulb, on the real photo, you will not see black outlines. So it's both unpleasant to the eye as well as unrealistic.

This is not about breaking reality or doing some hacks to meet deadlines. Actually, from my experience, less hacks and tricks, the easier it is to meet the deadline.

[lextorlex]

Well, in case of wallpaint the black wall looks really bad.. But it can be avoided using very high IOR and low reflectivity..

Now I know this isn't how you would like to go about materials, using some weird values, but in that scenario it is avoidable problem.

Nope, that's not a solution. You will completely change characteristics of that material. IOR 100 will mean there will be almost no difference between facing and parallel angle reflectivity. It will look like very dull aluminium, not wall paint.

It's like saying you can workaround refraction bug by using opacity instead of refraction.

lacilaci method with high IOR level can be emproved to avoid absense of difference between facing and parallel angle reflectivity. You just need to add a falloff map to glossiness slot using perpendicular/parallel and draw a user curve there, where at facing angles glossines will be close to almost zero and raised up to a specisied glossiness value (0.2 in the shown examples). It works just fine and doesn't not feel like very dull aluminium or smth.

[maru]

"Glossy reflections no longer darken material on edges"

confirmed ;)

But why is the scene so much darker?

[pokoy]

So rerendering an older scene will not match? That would be quite bad to be honest...

[maru]

So rerendering an older scene will not match? That would be quite bad to be honest...

Nope. You need to create a new material to make it behave differently.