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Chrome material, how?
 
I can't seem to find a way to edit the reflectivity of an object to make a chrom material. only thing i've found is to jack up the IOR, but that doesn't seem like the right move.

In c4d i would make the diffuse black and then control the color with the reflection color. here that doesn't seem to work..

tried with both standard material and node one.

By the way is there a material demo collection or something? To use as reference?
Edited: aleksey voz - Jun 10, 2021 17:55
 
Administrator  Posts: 523
Jun 10, 2021 19:26
Quote
aleksey voz wrote:
only thing i've found is to jack up the IOR, but that doesn't seem like the right move
Why not? It's pretty right method. The material layers are stacked this way:
1) Reflection1 (layer weight is multiplied by the weight computed from IOR)
2) Reflection2 (layer weight is multiplied by the weight computed from IOR)
3) Transmission (only weight value)
4) Translucent (only weight value)
5) SSS (only weight value)
6) Diffuse (only weight value)

Each layer weight determines the portion of layer contribution stack based (high level layers with largest priority).
E.g. the first layer has weight=0.3, then all underlying layers have 1-0.3=0.7 multiplier.
For example, the second layer has 0.4 weight setting, while after the first layer reduction it means the second has 0.7*0.4=0.28 contribution in total.
While the layers below the second one have 0.7*(1-0.4)=0.42 weight, and so on.
So if you make weight=1 for top layer you will hide underlying layers.
This way you can make a glass, with reflection1 and transmission with same IOR values, you can make different IORs if you want. You may stack two reflections on top of transmission.
The Color value is used to multiply reflectivity after layer contribution is determined by weight x IOR_weight. The Color doesn't make space for other layers, everything is controlled by weights and IORs for reflections.

To make Chrome you can make Reflection1 weight=1, IOR=20 or 50 (for example) and Color with some slight blue tint, roughness=0. The second reflection may have larger roughness=0.3 white color.

Other rendereres have same material rules, but sometimes there is metallic/conductor IOR with additional to IOR setting. This can be replaced with just high value of the current single setting IOR.

Quote
aleksey voz wrote:
By the way is there a material demo collection or something? To use as reference?
I am going to write an online documentation on materials after 0.65 release is out with shaderball examples, how to make metals, flakes, glass, wood facture with procedural noise. For example 0.63 with nice fixes is almost ready.
 
I guess it works. I just felt like IOR had some other physical significane, since in other renders it doesn't quite work like this. they have these charts for setting the right ior for the each material: https://pixelandpoly.com/ior.html

But i guess it works :)
 
Administrator  Posts: 523
Jun 11, 2021 14:12
This is due to existance of 2 Fresnel IOR modes: dielectric and conductor. Ours is dielectric at the moment. Conductor is for metals and it has complex value (2 settings ior and k, and 1 switch between modes). Fresnel dielectric can mimic conductors with high IOR values and look similar but with less controls (and less real physics). Renderers usually have either one or both modes. Not a problem to add conductor, I just wanted to make material GUI simpler, however it already has many other settings, especially that long material box in node editor canvas :)
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