[Gary Bidwell]

I'm using the material wizards to create a plastic material and noticed the reflectance 0 colour is the same as the reflectance 90 degree colour.
This is incorrect as the base layer should also exhibit some fresnel effect i.e. the 90 degree colour should be brighter.
Even a piece of diffuse non coated white paper will show the fresnel effect.

The same thing happens on the car paint wizard, no fresnel on the base layer. Why is this?

Thanks.

[Half Life]

force fresnel will take care of that.

Best,
Jason.

[itsallgoode9]

I may be wrong, but I believe he's asking about "Whym in a physically correct renderer would the wizard materials have physically incorrect properties?" Correct me if that's wrong. If that's the case, I have wondered the same thing myself, quite a few times. The carpaint thing especially puzzled my mind many times.

[Gary Bidwell]

yes itsallgoode9. I find it puzzling also. Can anyone give a valid explanation?

Thanks all.

[Half Life]

I don't have a problem with that since the force fresnel option corrects any "incorrect" issues -- and chances are none of us were hitting the correct fresnel relationships with our "custom" settings to begin with... ND is now a much more correct indicator of the strength of the fresnel effect which I think is better overall for accuracy and certainly easier to understand.

What is messing with me on some of the wizards is the heavy use of additive blending mode which is known to cause extra noise and slower to clear materials -- basically because if you start with lighter or more saturated colors we are getting outside the natural range of light reflected from those surfaces after you "add" more light to the mix.

Of course I may be waaaaay off base as I'm still testing alot of aspects and nothing with Maxwell parameters exists within a vacuum -- everything is inter-related so the wizard materials could be compensating for some issues I'm not aware of.

Actually my primary frustration with Maxwell materials is I cannot figure out how to simulate a thin strongly-colored transparent "dye" layer, which would be the correct way to simulate things like anodized aluminum and car paint metallic flake... something like a "multiply" blending mode seems to be needed for this to happen.

Best,
Jason.

[Gary Bidwell]

If force fresnel is the correct solution, and I guess it is, then why isn't it on by default when using the wizards?

If I create a new mxm the 0 and 90 colours are grey 0 and white 90, not grey 0 grey 90.

All sightly misleading and confusing. Can anyone from Nextlimit clear this up?

Thanks for all your help.

[tom]

OK, here comes the answer. Because, fresnel is only defined for perfect specular (rough 0) surfaces. At high rough like 97 in plastic wizard, fresnel equations are not valid, therefore no such falloff is expected. As an experimental approach, Maxwell is blending out the fresnel effect along roughness.

[Gary Bidwell]

Thanks for the explanation Tom. So why does a default mxm with a 100 percent roughness value have reflectance values 153,153,153 at 0 degrees and 255 pure white at 90 degrees? Should this be amended.

I guess theres no harm in selecting force fresnel on the base layer, especially as I normally lower my roughness parameter.

Do you have plans to implement a more complex car paint shader as I miss the control I have in mentalray, especially the flake parameters like flake scale, density, weight, reflect, decay etc.. Also Lit colour, the color seen in the area facing the lightsources.

Thanks.

[zdeno]

In 1.7.1 version when LAMBERT mode was selected (100% roughness then refl 90 color and Nd was not taken to computation).

BTW leaving pure white in refl 90 is the most common mistake with maxwell, but NL don't know how to edit simple manual.pdf

asking questions about material creation from NL is pointless, it seems like they really don't know how it works, or don't know how to post on this forum. Rather try to ask some gifted users who have renderfarms and spend trylions hours to break this material system. I set some thread about doin real looking materials but only one answer from Tom and one from Mihai I get. Everything what is important in maxwellrenders are materials, anything else is just technical stuff. Leaving this questions without answers is bad. Then we see alle those flat all lambert renders in WIP section

This psyhical or physical approach is NL's shot in own foot. Maxwell material system is opposite to WYSIWYG concept. The most annoying is mix beetween roughness, Nd, and Reflection color. You have to be very talented in maths to achieve needed color of reflection. Change in any relfletion color need to be compensated in roughness and Nd to stay on course. There were some standards in CG like specular reflection, glossy, opacity, but maxwell just tried to write a bible again.
for example - I can tell how pavement looks how is it colors and there is no specular, but how in the .... I can tell how many BSDFs it need and what roughness is any one of them , and Nd crap. It is all riddles all the time.

but in 2.0 i heard it starts to look more normal , like this force fresnel stuff. Must try sometime.

[tom]

So why does a default mxm with a 100 percent roughness value have reflectance values 153,153,153 at 0 degrees and 255 pure white at 90 degrees? Should this be amended.

It could be red, too but, then you'd maybe ask why it's red. So, theres is no special reason. Because, if you see my above explanation again, grazing angle (ref 90) has no effect when roughness is 100. Let me know if you suggest doing it in another color.

I guess theres no harm in selecting force fresnel on the base layer, especially as I normally lower my roughness parameter.

Yes, there's no harm and you can also alter ref90 depending on purpose.

Do you have plans to implement a more complex car paint shader as I miss the control I have in mentalray, especially the flake parameters like flake scale, density, weight, reflect, decay etc.. Also Lit colour, the color seen in the area facing the lightsources.

Why not. 2.0 carpaint is better than 1.7 carpaint and a future wizard could be better, that's for sure.

[tom]

There were some standards in CG like specular reflection, glossy, opacity, but maxwell just tried to write a bible again.
for example - I can tell how pavement looks how is it colors and there is no specular, but how in the .... I can tell how many BSDFs it need and what roughness is any one of them

There are some standards in real life like oil paint, brush, canvas, turpentine, but maxwell maxwell is a render engine.
for example - I can tell how apple tree looks, what color it is and how much specular on it, but how in the .... I can tell how many oil colors do I need, how should I mix them and how much pressure should I put on canvas using which brush....

[Gary Bidwell]

Good points Tom. Thanks for all your help.