need shader/material explanation

[dave62]

hi everyone,

i am looking for some more detailed info how to setup materials correctly.
Especially when to use glossy or diffuse and how to set glossy and roughness values?
Is there any list available with glossy/roughness settings for specific materials?
What are the advantage/disadvantage of each setting (no fireflies, long render time,...)?

Hopefully someone could explain further shader setting details.

Thanks in advance dave

[matej]

diffuse -> surfaces that scatter light (more or less evenly) in every direction -> rough wood, fabric, paper, almost everything unpolished / rough...
glossy -> surfaces that scatter light rays more in a certain direction -> metal, varnished wood, paint, plastic, almost everything shiny...

Roughnes means, well, how rough is the surface

* higher values -> bouncing light rays are more scattered -> matte surface
* lower values -> bouncing light rays are more grouped together -> specular / mirror surface

Specular parameter of glossy material tell something like how much the surface reflects the surroundings (energy of bounced light rays) and roughness could be something like how sharp is the reflection of the surroundings (direction / grouping of bounced light rays).

Diffuse shader is faster, but it doesn't matter, because you can't use it for a glossy surfaces. You use what you must.
Generally, if you can see the reflection of light source in a surface (even a little) = glossy shader

[dave62]

hey matej,

thanks a lot for your detailed explanation!

quote: "...Generally, if you can see the reflection of light source in a surface (even a little) = glossy shader..."

Would you choose difuse for a woodchip wallpaper though?



I hope i will produce more realistic renders soon..


thanks again dave

[matej]

quote: "...Generally, if you can see the reflection of light source in a surface (even a little) = glossy shader..."

Would you choose difuse for a woodchip wallpaper though?

If your wall is painted, a glossy with low specularity and high roughness would probably be more realistic.
Try both though, and see what results are you more satisfied with.

[dave62]

I thought its good to keep the amount of glossy materials in my scene low to speed up rendetime.
Yep, i will try which setting the material needs to look more realistic
Do you know which circumstances in your scene (light/shader) could cause a lot of fireflies?

[matej]

Do you know which circumstances in your scene (light/shader) could cause a lot of fireflies?

Strong bumpmaping is (used to be?) one of the causes of fireflies.