[rivoli]

WTF?!?!?

that's what I thought, but I totally loved that part about chainlike molecules..

[giacob]

So why can Maxwell not simulate a simple homogenous plastic of whatever shinyness with only reflectivity and roughness? When you get to the indepth discussion of layers, it would be helpful if you would explain in detail the relationship between the first bsdf and the second one and why a surface's roughness needs to be represented on a separate layer if the shine is simply a result of that roughness. It just seems like a quirky workaround to me until then.

Well I imagine it this way: You have a rough plastic material, the surface is rough enough that it looks almost like a lambert, no sign of specular reflections. Now you start polishing it's surface, you are aligning a very thin "layer" of this material so that it gives you specular reflections, but much light will still go through this first smooth part and bounce off the rest of the material, which is more porous, so that light will be reflected back more diffusely.

In any case, I don't find this system overly complex, and we could ask the same question for any other renderer. Why do I need to set a separate diffuse color, and a specular reflection? Would such a material also look correct, because the more an object reflects back light as specular, the less it reflects back it's own color. Instead it reflects back the environment. This is taken care of in Maxwell. This material system is not complex, just different.

There's just too much panic, while completely ignoring that a LOT of materials you find in real life could not possibly be made with the old system.

mihai .. other render dont claim themselves to be phisically correct.. so in this case i am trying to understand if this phisically correctness really exist.. and does have a corrispondance in nature... anyway also a practicall explanation as the one of Rivoli, would do the same...

[Frances]

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[aitraaz]

but I totally loved that part about chainlike molecules..

[RonB]

Well, Mihai's points regarding the make up of plastics are well taken. But it does come to mind that how often in fact for, say product illustration, will it be necessary to actually be that scientifically accurate to render a shot with a plastic componant to it? Seems a bit nit picky to me to have to spend all that time compounding a texture with 5+ multiple layers to look resonably like plastic...Sort of killing flies with a shotgun isn't it? There are better things I would rather spend my time on...modeling, lighting, scene set up. Seems there should be an easier way.

Just my thoughts...Cheers, Ron

[aitraaz]

Here's some useful tips:


A plastic tube is charged by rubbing it with fur. The plastic tube acquires a negative charge.

In an atom there are the same number of protons as electrons and so the atom has no overall charge (since the positive charges of the protons is effectively cancelled out by the negative charge of the electrons). It is very difficult to remove protons from the nucleus but it is relatively easy to remove at least some of the electrons. If we remove one electron then the atom (or more accurately now the ion) will have a single positive charge since it now has one more proton than the number of electrons. This gives us a clue as to why some materials are good conductors whilst others are poor. In conductors electrons are fairly free to move and so we can have flow of electrical charge. Again this gives us a further clue. If we are looking at the flow of electric charge (rather than simply the flow of electrons) then if we have ions which are free to move then we can have an electrical current.

[giacob]

Here's some useful tips:


A plastic tube is charged by rubbing it with fur. The plastic tube acquires a negative charge.

In an atom there are the same number of protons as electrons and so the atom has no overall charge (since the positive charges of the protons is effectively cancelled out by the negative charge of the electrons). It is very difficult to remove protons from the nucleus but it is relatively easy to remove at least some of the electrons. If we remove one electron then the atom (or more accurately now the ion) will have a single positive charge since it now has one more proton than the number of electrons. This gives us a clue as to why some materials are good conductors whilst others are poor. In conductors electrons are fairly free to move and so we can have flow of electrical charge. Again this gives us a further clue. If we are looking at the flow of electric charge (rather than simply the flow of electrons) then if we have ions which are free to move then we can have an electrical current.

thanks aitraaz .. now i fully understand...

[adamwade]

It seems like the simplicity of setting up a MW rendering was achieved by accurate lighting, but now the materials are a bit out of hand. I have been TESTING for weeks now and still don't really get it. It's sad to think that my renderings are now not realistic looking only because of this new material system being difficult.

Using the Material wizard is a great idea for some of us perhaps, but ultimately it is frustrating not to understand.

I would say that for plastics the surface and highlights are all detirmined mostly by the surface texture that they are molded in. In theory just using different bump maps on a high gloss material could get you any normal finish you would find on a product. (of course soft rubber and a hard plastic would be pretty different if shot into a polished mold, but you get the point.) With tiny microscopic bump maps being limited by resolution I think we use tools like ND and roughness settings.

I other renderers we are often given built-in procedural bumps that we are all so used to for making fine textured materials, but its all different now.

Mihai is kicking butt to help us understand and it's great ! Thanks

[Hugh]

Its all about light as mihai says.

The goal of Maxwell is physical correctness, which is admirable and what I've always looked forward to seeing in a renderer.

-Maxwell renders the light spectrally, no question, physical.

-Maxwell represents the camera with a shutter/lens system and film iso, again physical.

-The light sources must all have area and are defined with real world units, physical.

But what about the materials. If I wanted to create for example a white paint finish with 30% gloss and a total reflectance of say 70%, it would be trial and error until I get the correct look. Where's the physical correctness in this? How are you supposed to define a physically correct material if such a basic property as total material reflectance is pure guesswork. Its all about light, REFLECTED by materials, its how we see the world. In the maxwell world, everything can be physically defined, apart from the one thing that we see.

I'm guessing that this IMHO essential feedback on material properties will eventually be covered by the 'material info' button, below 'material layers'. Without this, there is no physical correctness that I can see, just aesthetics. Why this important feature isn't working in the supposedly finished 'Light Simulator' is anyones guess.

Sorry for the negativity, but I thought this would all be sorted with the release of V1.

[KRZ]

i think that maxwells materialsystem is actually one of the most simple, genious editors. think of all the other renders where you have a special materials for every special case. in maxwell you only have 1.

the two layered approach for plastiks is mostly because of coloured "highlights" that are a charakteristic for most plastics. with only one layer you could not define "highlight"-color.

what i not yet understand is why the wizard-generated plastik materials has at the base-layer a nd1 and why the two layers are mixed with the adaptive method. right now i believe this to be wrong and always change it to nd3 and blendmode "normal".

i hope to learn more about this in the next episode of this material-faq.

[rivoli]

what i not yet understand is why the wizard-generated plastik materials has at the base-layer a nd1

I don't know, but I guess it doesn't really make any difference since that bsdf is a full lambertian.

[Frances]

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[MANorth]

No offense to anyone involved in this discussion, but there is a pretty complete tutorial on the two BSDF system in the manual, complete with a visual chart of various different weighting percentages. (p. 82) It helps a little to get past the counter-intuitive nature of the two-layer system. It doesn't help at all in deciding if it's "accurate" or not.

[adamwade]

Francis, I think you are right.

Let's face it, for the most part everyones materials in the beta looked dead on right. Not as much control or flexibilty to create, but you could get it right with 2 or 3 test renders.

Were all the beta materials always using accurate IOR data? Maybe that's why it was easier to make them look real.

Perhaps using more IOR files would reduce MY time, but increase the computers time in rendering hours.

[lllab]

well Frances i must say i think you are not right.

i also think it is the most simple system, and for me the first logical one. i always felt materials should deal with reflection/roughness and falloff.
just look to the world around you. with some basic knowledge about color, physics etc i see the maxwell system the most near one to real nature.

maxwell system is it for me. ans yes i mean version v1 not the limited beta stuff. (i dont like the premade materials much).

obvious there are some people here that prefer the classic render channels.
or a simplified system like beta. it is true that we have to somehow re-learn materials. i myself are doing 3d since more than 12 years, it took a few days to get into it, but now i love it. ( and dislike the unlogical systems in my other apps)

at the end we have the choise to take whatever app that suits us most out there. but please keep this system NL. its great to my opinion.

cheers
stefan

edit: thanks Mihai for the great detailed explanation.