Forums » CentiLeo for Cinema 4D
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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: 774
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: 774
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 :)
 
What is the purpose of having two reflections?
Can you give an example of when this would be useful to have two for a material?
 
Administrator  Posts: 774
Dec 1, 2021 23:49
A lot of metalls can be nicelly implemented with 2 or even more reflection layers stacked on top of each other. Generally there is a medium glossy reflection 2 and clear mirror layer on top of that.
Reflection 1 can be a specular mirror coating with roughness = 0 and IOR = 1.5 while Reflection 2 may have higher fuzzy roughness = 0.3 with IOR = 2 and it will sit below the first reflection. Then a diffuse layer is placed with some color.
 
How would I use the 'metallic' texture for a metal texture pack?
I have the colour texture and glossyness and reflection which I know where to map in the material, but what about metallic?
Is that something I use on the reflection 2?
I tried but could not use it with any effect on the object.
 
Administrator  Posts: 774
Dec 4, 2021 15:16
Quote
ssjenforcer wrote:
I have the colour texture and glossyness and reflection which I know where to map in the material, but what about metallic?
CentiLeo has roughness, not glossyness. They are reverse to each other. You either reverse the glossyness texture using output black = 1 and output white = 0 or enable "Use glossyness" flag in material settings.
As for metallic - it's not directly supported right now, it can be used to tune behavior of reflection parameters. I will make a slot and a mode for it. Currently the picture of metallic can be assigned to IOR, but the range of bitmap metallic should be adjusted, because for metals the IOR should be larger than one. E.g. you can experiment with metallic bitmap output black = 1.5 and output white = 4.0.
Reflection1 and Reflection2 are absolutelly the same reflection, but there are 2 of them one on top of another one to get more freedom in hand for various metal implementations.
 
Quote
Kirgman wrote:
Quote
ssjenforcer wrote:
I have the colour texture and glossyness and reflection which I know where to map in the material, but what about metallic?
CentiLeo has roughness, not glossyness. They are reverse to each other. You either reverse the glossyness texture using output black = 1 and output white = 0 or enable "Use glossyness" flag in material settings.
As for metallic - it's not directly supported right now, it can be used to tune behavior of reflection parameters. I will make a slot and a mode for it. Currently the picture of metallic can be assigned to IOR, but the range of bitmap metallic should be adjusted, because for metals the IOR should be larger than one. E.g. you can experiment with metallic bitmap output black = 1.5 and output white = 4.0.
Reflection1 and Reflection2 are absolutelly the same reflection, but there are 2 of them one on top of another one to get more freedom in hand for various metal implementations.
When I try to use Map black to 1 and Map white to 0 for the roughness map it takes away almost all the reflection from my material. I also don't see a flat for glossyness.

EDIT:
That only happens with a metal texture I used that had Metalness but no Reflection to map.
Edited: ssjenforcer - Dec 5, 2021 17:51
 
Administrator  Posts: 774
Dec 6, 2021 10:01
Actually to change the output range of Bitmap image the Map black/white can be changed. They help to scale or invert the image. This is an example of invert:


You can also change the distribution of the values between black and white colors of the image. For example this can be done using CentiLeo gradient node. Just look that middle grey values in the gradient ramp are changed to prefer darker values for the larger part of the input range.
 
Quote
Kirgman wrote:
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.
why use two reflection when making metals,and does Reflection 2 use the same IOR as Reflection 1does?
 
Administrator  Posts: 774
Aug 28, 2022 10:19
Quote
Wuzhongjian wrote:
why use two reflection when making metals,and does Reflection 2 use the same IOR as Reflection 1does?
It's defenitelly up to user to use one or two reflections. You can setup differernt IORs and roughness for them of course. This is done for artistic freedom
 
Quote
Kirgman wrote:
Quote
Wuzhongjian wrote:
why use two reflection when making metals,and does Reflection 2 use the same IOR as Reflection 1does?
It's defenitelly up to user to use one or two reflections. You can setup differernt IORs and roughness for them of course. This is done for artistic freedom
Just Checked this Topic againg finding out that you already answered this question detaily.Thank you for answer it againt
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