Which V-Ray feature should we bring to Corona?

[pokoy]

Oh, another one I totally forgot about, sorry if it's been mentioned already: please implement glossy reflections (optional per material switch would be best), that one really adds a lot to rough reflective surfaces.
EDIT: I meant glossy fresnel, of course.

[Juraj]

Oh, another one I totally forgot about, sorry if it's been mentioned already: please implement glossy reflections (optional per material switch would be best), that one really adds a lot to rough reflective surfaces.

Do you mean rough fresnel or something else ?

[pokoy]

Ah sorry, I meant glossy fresnel, where reflections get sharper with grazing angles.

[Juraj]

Ah sorry, I meant glossy fresnel, where reflections get sharper with grazing angles.

Ah I was confused because this is Vray feature thread and they only implemented rough fresnel which Corona already had for some time :- ).

But glossy attenuation towards edges is fantastic feature and imho only F-Storm (and Disney) have that natively in some way.

[danio1011]

Ah sorry, I meant glossy fresnel, where reflections get sharper with grazing angles.

Ah I was confused because this is Vray feature thread and they only implemented rough fresnel which Corona already had for some time :- ).

But glossy attenuation towards edges is fantastic feature and imho only F-Storm (and Disney) have that natively in some way.

I'm confused on this one.  I remember when Corona rolled out their PBR mode which mean you wouldn't get that white haze at glancing angles and could go low glossiness with no worries.  Then VRay released 'glossy fresnel' which I thought was the same thing (but I was never sure of this)?  And there is a third thing in play it sounds like only with Disney?

Could you explain further Juraj?

[Juraj]

Yeah there are two(or 3) things, and neither has exact name so every renderer has named it differently, or didn't give it name at all :- ).
Here is brief summary (sorry for off-topic to anyone):

- Glossiness or Roughness range : This described how rough a material can get. Previously Corona with Glossiness 0 was something equivalent to 0.4 in fact, it was still very glossy, definitely not fit for paper/sand/etc.. SOLVED in both Corona and Vray.
- Specularity intensity based on Fresnel: Both Vray and Corona had BRDF which didn't properly dim the specular intensity when glossiness was getting lower. So 0 glossiness was literally shining (the haze), when it was supposed to be almost fully flat. SOLVED in both Corona and Vray
- Glossiness value changing based on fresnel term. This is effect that makes materials more glossy (mirrory) towards the grazing angle even if they are rather dull otherwise. Disney calls it "retro-reflection" in short, and it can actually work both ways, making dull/rough materials more shiny at grazing angle, and opposite, shiny materials getting little bit more dim at grazing angle.

Neither Vray or Corona supports the last feature through some exposed parameter. F-Storm currently does support it, although I don't think it's part of BRDF, so you can simulate the same effect yourself manually by placing your glossy node network (or simple texture/value) into fresnel node.

[danio1011]

Yeah there are two(or 3) things, and neither has exact name so every renderer has named it differently, or didn't give it name at all :- ).
Here is brief summary (sorry for off-topic to anyone):

- Glossiness or Roughness range : This described how rough a material can get. Previously Corona with Glossiness 0 was something equivalent to 0.4 in fact, it was still very glossy, definitely not fit for paper/sand/etc.. SOLVED in both Corona and Vray.
- Specularity intensity based on Fresnel: Both Vray and Corona had BRDF which didn't properly dim the specular intensity when glossiness was getting lower. So 0 glossiness was literally shining (the haze), when it was supposed to be almost fully flat. SOLVED in both Corona and Vray
- Glossiness value changing based on fresnel term. This is effect that makes materials more glossy (mirrory) towards the grazing angle even if they are rather dull otherwise. Disney calls it "retro-reflection" in short, and it can actually work both ways, making dull/rough materials more shiny at grazing angle, and opposite, shiny materials getting little bit more dim at grazing angle.

Neither Vray or Corona supports the last feature through some exposed parameter. F-Storm currently does support it, although I don't think it's part of BRDF, so you can simulate the same effect yourself manually by placing your glossy node network (or simple texture/value) into fresnel node.

Ah perfect, thank you Juraj that's very helpful.  So I'm guessing that the 2nd point is what Corona calls PBR mode and VRay calls 'Glossy Fresnel'?
https://labs.chaosgroup.com/index.php/rendering-rd/understanding-glossy-fresnel/

Point 3 sounds interesting.  I wonder what types of materials this would be useful on?

Cheers,
Daniel

[Juraj]

Yup, Corona called it PBR because we had neither the range (1) nor the spec (2). Vray called it rough fresnel because they only missed the (2).

Regarding 3 I pondered that idea myself and you can check the examples in Disney paper (the latest appended one about their PBR progress) where they took a look at the MERL data set ( 100 scanned BRDFs from real-world materials ).
It's definitely not universal as not all materials show it, and not even the same category ( it would be logical if it was limited for example to composite, coated type of materials, but it isn't).
It seems like it's very much "if you can see it with your eyes, it's there" kind of effect, so it would be more artistic control.

I personally used it so far dominantly on woods. Woods are often (unless polished or coated) rather rough materials, but at grazing angle they can shine rather strongly. Though lot of this has to do with special anisotropy we can't simulate yet.
I also add it to plastics.

[danio1011]

Yup, Corona called it PBR because we had neither the range (1) nor the spec (2). Vray called it rough fresnel because they only missed the (2).

Regarding 3 I pondered that idea myself and you can check the examples in Disney paper (the latest appended one about their PBR progress) where they took a look at the MERL data set ( 100 scanned BRDFs from real-world materials ).
It's definitely not universal as not all materials show it, and not even the same category ( it would be logical if it was limited for example to composite, coated type of materials, but it isn't).
It seems like it's very much "if you can see it with your eyes, it's there" kind of effect, so it would be more artistic control.

I personally used it so far dominantly on woods. Woods are often (unless polished or coated) rather rough materials, but at grazing angle they can shine rather strongly. Though lot of this has to do with special anisotropy we can't simulate yet.
I also add it to plastics.

Great!  All very clear, I've been wondering about that for a while.  Thanks!

[Dan Rodgers]

-Vray Bump Mtl (do not mistake with bump map)
https://forum.corona-renderer.com/index.php?topic=16770.msg108484#msg108484

+1 for BumpMtl  - I used to use all the time with VRay.

VRay Plane / infinity plane equivalent.

'Reset on render end..' option for CoronaDR  (we regularly have problems where we have to go around all nodes and restart CoronaDR for them to start picking up)

+1 for Aerial Perpective

VRay Environment Fog   or improvements to current volumetrics

[Jpjapers]

Buy more Ram, F**k the bucket

This is an amazing sentence and should be the corona mantra.

[matsu]

I moved from Vray to Corona a year ago. I work exclusively with archviz, and often close to the architect, which means a lot of sketching and trying out early design drafts.

There are so far only three things I really miss from Vray.

1. Vray toon. Great to get those "hidden line" renders that work very well when doing "npr" images.

2. Clean masks. Vray always produce perfectly clean edges on the render elements. Corona's are very noisy, and working with them in PS is not as nice.

3. 2D displacement. Often worked even better than 3D displacement, was quick to render and used little memory. Being the memory hog it is, Corona should really try to implement this technology.

Then there are little things, like being able to use the "shellac mode" in the layered material. In spite of it being "unrealistic" it's very useful for creating a coat of varnish on another material.
The aerial perspective was rather nice too, but I think Corona's global fog is better, even though it's not "free" the way aerial persp is.
Vray plane was also rather useful. 

[Jpjapers]

Vray clipper!!!

[Nariman]

The questions is simple - V-Ray has solved a lot of problems before us, and now we have access to those solutions. What feature that V-Ray already has would you like to see in Corona? Note that this is just for our inspiration, and we don't have time to do much porting before 1.7 release, so we are talking about 1.8 and later

DEEP DATA SUPPORT

[shiftman2012]

1.Angle dependent material glossiness. (Vray Material Glossy Fresnel option)
2. Dynamic and Auto memory limit. To Have option to limit RAM usage on machines with less than 32gb ram. It will make starting slower but renderer will not run out of memory. Maybe You Can Even improve this feature to be better than in vray.