Does anyone use Reflection amount parameter in VRay MTL?

[Karol.Osinski]

Hey guys, I wonder how many people make use of Amount parameter for the reflection of the material (also for diffuse). I personally avoid it, as in my opinion it has not much to do with an actual surface in reality and it is just not the way I like to approach material creation (I would say I am on the edge of "bro science" with these things), I would rather play around with both glossiness and reflection maps in order to have more control of my material. On the other hand some of my collegues rely on it most of the time and I don't support it, but I don't wanna be ignorant because if it exist in Maya it must has its reason. I would appreciate your thoughts on it guys.

Have a great day.
K.

[fixeighted]

I'd like to hear comments also.
From what I've learned, apart from using it for artistic/stylistic/lazyhacky type reasons, then everything needs to be 100% reflective and to then have that perceived reflectivity controlled by glossiness/roughness etc.
Would love to know if that's actually correct or not.

[Muhammed_Hamed]

It serves as a multiplier to diffuse/reflection colors, I never touch it honestly (unless I wanna turn off my reflection maps for whatever reason, instead of disconnecting them)
Honestly I think there is no right or wrong here, some people might prefer to use it.. while others would do that through diffuse/reflection color directly(myself included)

I feel this makes sense for Arnold where the range of diffuse or specular could go over 1 maybe?(so you don't want that to happen for energy conservationi)
This is different for Vray, it will clamp the colors to one for diffuse/reflection/refraction

And this parameter doesn't exist in Max for example or Houdini or Modo.. it is only present in Vray Maya..

[seandunderdale]

Before reflection value result was linked to glossines (pre Vray next?), how would you make a very dull reflective material? Are you saying you would use the reflection color instead of amount, or have a very low IOR like 1.2? My way of making a tyre rubber, or car plastics of varying reflectivity, would be to always leave the reflection colour to white, set ior to 1.48 (ish) and then have different reflection amounts to control their values.

Now glossiness controls the result of the reflection intensity, it makes more sense to rely on that + ior more to control the end result.

[Karol.Osinski]

Thank you for your input guys. fixeighted , well I've heard oo that in theory everything is supposed to be 255 reflective and rest should be controlled with gloss / roughness + IOR. One o the sources is coming from this forum, I wanna find that topic now , And I gave it a try but I wasn't really happy with highly reflective results, together with riddiculous performance drop in Maya viewport when material is highly reflective but dull... (the trick with unflagging "Computer Environment Reflections" - but I notice it doesn't always work).

seandunderdale When it comes to Maya I only worked on VRay Next, it is hard for me to imagine how glossiness would not be linked to reflection. Do I miss something?

[fixeighted]

I didn't intentionally want to mislead but I am on Max not Maya, so didn't realise the parameter is not there in Max.
I use the approach in most materials now but sometimes just don't have the necessary maps to do it properly and no time to make them, so
y'know...whatever works

[seandunderdale]

Glossiness has always been linked to reflection, but "use roughness" which links glossiness to perceived reflection value hasnt. Prior to "use roughness" being implemented, the glossiness would blur the reflection, but not dim it. Using glossiness + amount was how you used to (still do sometimes) dim the reflection when it was blurred.

[SonyBoy]

Purists and those wanting to be "technically" right would say all surfaces should be 100 percent reflective, yes, as the only way we see objects is via reflected light. The light we don't see is what gives an object its color. Artists like Grant Warwick take this approach. On the other hand, as I understand it Vray is NOT a technically accurate renderer as it is biased and therefore everything is kind of a cheat anyway. What matters is what looks correct. So there is really no right or wrong way to approach this if it gets you the results you want.

[Muhammed_Hamed]

Artists like Grant Warwick take this approach

In his videos, he doesn't use 100% reflection .. he usually maps it with textures/procedurals or sets it to 80% or 50% otherwise

But yeah, I agree that what matters is the material looking correct(within PBR whenever possible). For me personally I only use 100% reflection color with metalness.. for everything else I don't

Vray is NOT a technically accurate renderer as it is biased and therefore everything is kind of a cheat anyway

I don't think it matters ..every renderer is biased like what Vlado explains here
https://www.chaosgroup.com/blog/the-...ased-rendering

[SonyBoy]

When you think about it, what he says is a no brainer really. EVERYTHING created in CG is to some extent a cheat -- materials with things such as bump mapping are faking surface imperfections, for example.

[Karol.Osinski]

Before reflection value result was linked to glossines (pre Vray next?)

Glossiness has always been linked to reflection.

A bit of confusion there but I got your point :P

Anyway, to create a dull, reflective material I would play with reflection map and lower the GGX tail off parameter in this case. When it comes to Roughness...I've people such Adan Martin (spelled his name without spanish accents, sorry) suggested making material duller by using introducing a little bit of Roughness value...although that he did in 3ds max where I believe Roughness parameter works the way Metallic in Maya - does not break the specular workflow and you can freely just add a bit of it on the top of your material. On the other hand in Maya once you flag the USE ROUGHNESS, your GLOSSINESS map inverts so your material becomes extremely dull...

What matters is what looks correct. So there is really no right or wrong way to approach this if it gets you the results you want.

I agree...but some extend, In my opinion it is useful to have a solid base to start with - many people believe it makes things more difficult and overcomplicated but it is actually the opposite. Knowing how surfaces react with light in reality helps a lot to predict how they behave inside the render engine. Once you get the base correct then modify it further down in order make it look good inside your scene.

What I find by observing people, many tend to play around blindly with material parameters until they got it right without really knowing what these knobs are doing...After all that material look GOOD inside their scene. Although, when it comes to reproducing the material, you make it the same way you did it before by faking it and taking shortcuts and suddenly it looks totally wrong in the other scene - so you play around with all these parameters again.

On the top of it - it is way harder to explain the material creation to someone new without having a solid base workflow.



I mentioned a bit extreme example above but not far from reality, at least from my point of view.

[Joelaff]

Don't forget the concept that if it LOOKS right, it IS right. There is reality, and then there is PERCEIVED reality. We typically have to cater to our audience's sense of PERCEIVED reality.

For example, people think water is blue (it reflects the sky, which is typically blue/cyan).

It helps to know the rules before breaking the rules, but back in the old days we had to make our own Fresnel like effects with complimentary gradients, etc. Everything is a cheat... until you get caught!

[Karol.Osinski]

Thank you Joelaff !!! ; )