[Eric Lagman]

Ok I have a few questions in regards to plastics. In particular black plastics. It seems like a lot of my plastics from 1.7 are looking different when I bring them in and render them in 2.0. I know the additive plastics would need to be tweaked, but I did not think that ones with a single layer and two bsdf with normal blending modes would need to be modified. Edit I think this is because of the color correction in v2 so disregard this.

With version 2 it looks like there are two methods to do plastics now as mentioned on pg 111 of the manual. One being the old way with one layer and two bsdf in normal blending mode, and the second being two layers with the topcoat set to additive for glossiness. My question is what is one methods advantage over the other? I noticed at the end of the manual the additive method will create more vivid colors. I create a lot of plastics doing product design, and am interested in getting one method (the best) down for creating realistic plastics.

I also noticed in the manual on pg 111 it says "Avoid having more than one layer set to a weight of 100 in Additive mode" Yet when I look at the abs plastic black that is provided, and also create a plastic from the wizard both have the additve approach and the layers are set to a weight of 100. Maybe not the abs black though because it has a noise weight map for the additive layer. That also confused me as to why that was done that way. Wouldn't you want the additive layer to affect the whole surface of the plastic, and get variation in the surface through just the bump map, and possibly a roughness map.

Also the method of the 90 color seems to be different now on the wizard and provided materials for the glossy layer of plastics. In 1.7 a lot of the plastics had a light color (almost white in the 90ref) for the glossy bsdf. Now it seems like the glossy layer or bsdf should just be dark, and control the reflectivty with the nd and force fresnel checkbox. Does that sound correct for doing plastics?

If any of the experts Tom or Mihai could shed some light on this it would be appreciated. I want to get the best method down and use it on all my plastic parts.

On a side note I have a quick question on rubber parts. Is it best to just take a regular plastic and mess with the r2 values to get a rubbery look. I use a lot of rubbery/overmold plastics in grip and touchpoint areas of products, and it would be helpful to know the best method of achieving those also.

It looks like there is a lot of good info on the think website in regards to version 2 materials so I will check out those videos. I thought it would be good to ask here just in case my questions are not covered there in the tutorials.

Edit: I watched Mike Vertas 2.0 material and am now more confused about the glossy layer of a plastic than I was before. He used the standard single layer approach through most of the tutorial for plastics, and the glossy layer always had the 0 and 90 values in the lighter greyscale range. Is this because he did not mess with the force fresnel option? The default plastic wizard uses force fresnel on that layer and has the 0 and 90 colors at 0. This gets even more confusing because he put the nd for the glossy layer at a range of around 20 using the single layer method. The wizard puts it a 1.25 range using the force fresnel. Towards the end he mentioned that he creates plastics using the same method as the wizard with two layers in additive mode, which from what I am seeing in the wizard takes a totally different approach on that glossy layer than the single layer method. Can one of the experts please clarify some of the conflicting info on the glossy layer of plastics. I am thinking the key lies with the force fresnel checkbox.

[Hervé]

simple...

BSDF's always blend
Layers always add

[Eric Lagman]

simple...

BSDF's always blend
Layers always add

Herve I was already aware of that. I think I may have rambled too much in my inital question. The more I played around with it I realize my question really is about the glossy layer in plastics. Is it a good idea to use force fresnel with dark ref 0-90 and a lower nd vs no force fresnel and lighter grey tones for the ref 0-90 with a higher nd? I have read the manual on force fresnel many times over, but it is still not clear to me how the nd should fluctuate based on whether or not force fresnel is checked. I guess the wizard for plastics is set up better now so if no one can answer this I will just use the wizard for my plastics.

Is it safe to say that any bsdf that does not have a texture just go ahead and use the force fresnel with a lower nd. Setting high nd for the glossy layer was just a workaround in the old version? It would be great if the manual went a little more in depth and gave more examples on the use of force fresnel, and the relationship of it to nd.

[Bubbaloo]

Is it safe to say that any bsdf that does not have a texture just go ahead and use the force fresnel with a lower nd.

That is my understanding of it.

[Mihai]

I also noticed in the manual on pg 111 it says "Avoid having more than one layer set to a weight of 100 in Additive mode" Yet when I look at the abs plastic black that is provided, and also create a plastic from the wizard both have the additve approach and the layers are set to a weight of 100.

Meaning if you make for example a 3 layer material, and the two top layers, you set them to additive with both their weights at 100. The bottom most layer in a material will always render in normal mode, even if it's set to Additive.

So the plastic wizard creates a two layer material, and uses only the ND to control how reflective the "topcoat" of the plastic is. When force fresnel is on, Maxwell only uses the color of the refl0/90 and disregards their value (brighter/darker). So even if they are set to black, having an ND >1 means the reflectivity is determined only by the ND. With force fresnel off, it uses both the color and value of the refl0/90 in combination with the ND you set to create the final amount of reflection. The refl0/90 and ND can be confusing because they both really determine the amount of reflectivity. A brighter refl0/90 color would mean a more reflective surface, and the same with a higher ND. So why have force fresnel as an option? Because in case you want to use a texture for the refl0/90 slots, controlling the amount of reflectance only via the ND could mean you lose some color from the textures, especially with brigher colors in the texture.
Force fresnel should be used for metals, and when you want an equally reflective surface, and not have that dark spot at 0° viewing angle which happens when you're creating a mirror surface and the refl0 color is set darker than the refl90 color. Force fresnel also allows you to work with more realistic ND values. Try for example creating a plastic with the wizard at 100% shinyness, and 10%. It's only the ND value of the topcoat that changes slightly. So it can be easier than fiddling with refl0/90 colors to change the reflectivity.

[Eric Lagman]

Ok that helps a clear things up quite a bit. Thanks Mihai. I always hated that dark spot in the middle of my plastics with 1.7 so I will definately be using the force fresnel on all my materials unless they have a texture map in the ref 0/90 slots. Yeah I noticed how the ND values are much lower in wizard materials whenever this option is checked. I found a list online though that maximus posted showing a huge list of materials nd values. http://forums.cgsociety.org/showthread.php?t=513458 In 1.7 I was just throwing a 15-20 range nd on glossy layer of plastics and metals. My approach will have to change, but I think the results look better and more accurate doing it this way. This area was causing me the biggest confusion in material creation going from 1.7 over to 2.0

[Maximus3D]

If i can give you a general tip for surface recreation, plastics included. It would be to not only focus on the rules and numbers and all that during creation, sure it helps a lot but it will never push your material beyond the standard look. You need to use your eyes to actually see in what way light interacts with the surface and then translate that into your material. Let's call it the artistic touch!

/ Max

[Eric Lagman]

If i can give you a general tip for surface recreation, plastics included. It would be to not only focus on the rules and numbers and all that during creation, sure it helps a lot but it will never push your material beyond the standard look. You need to use your eyes to actually see in what way light interacts with the surface and then translate that into your material. Let's call it the artistic touch!

/ Max

I agree. Most of the time in the stuff I render that is achieved by adding imperfections and texture in the surface. When something is too clean and 100% scratch free it gives it away as fake.

[tom]

Mihai has already made an excellent explanation and I just like to add something. You can still use a texture in combination with Force Fresnel. In order to do it, you need to use the texture as the layer mask (see how Textured wizard works) and moreover you can use the same texture in reflectance slots for maintaining the color of reflections when needed. But keep in mind that, only the hue will be taken into account and that's pretty enough for controlling the metallicity of specularity.

[Gary Bidwell]

Mihai, when I create a new default MXM and set the 0 and 90 colours to the same value for instance RGB 8, 133, 161, Nd 3, force fresnel ON, Roughness 40. As I understand it changing the HSV's value parameter from a (V)alue 161 to (V)alue 10 should have no effect on the material, but it does the preview will go darker and lighter as I adjust the Value parameter. Is this a bug?

Also when in the MXM 0 and 90 degrees colour pickers if I change the HSV values from 190, 243, 161 to 190, 243, 10 then close the colour picker and reopen it the values have changed to HSV 192, 255, 10. Is this also a bug or is Maxwell losing the original HSV values when internally converting to and from RGB.

Thanks.

[Gary Bidwell]

OK after some testing it appears that any roughness value other than 0 is the reason the preview gets lighter and darker as I adjust only the value parameter with force fresnel checked.
So the statement 'When force fresnel is on, Maxwell only uses the color of the refl0/90 and disregards their value (brighter/darker).' is only completely true if Roughness is set to 0.

[tom]

Is this also a bug or is Maxwell losing the original HSV values when internally converting to and from RGB.

You're right Gary, it's a loss in accuracy during conversions and it will be fixed in the next version.

OK after some testing it appears that any roughness value other than 0 is the reason the preview gets lighter and darker as I adjust only the value parameter with force fresnel checked. So the statement 'When force fresnel is on, Maxwell only uses the color of the refl0/90 and disregards their value (brighter/darker).' is only completely true if Roughness is set to 0.

Again, you're right. The fresnel is only valid for perfectly specular (rough 0) surfaces. Although, it doesn't mean the effect of "force fresnel" completely disappears as roughness goes above 0. It's rather disappearing slowly as it goes more and more rough. Of course, more rough means the given ref0 and 90 colors will start to dominate.

[Gary Bidwell]

Cool. Thanks Tom.