Another Render Test

i have this habit of creating quick scenes to procrastinate before getting some actual work done. not that this is a very effective time to spend, rendering vases is imho rather a waist (then better do a real if you have the means), anyway inspired by this recent vase i wanted to give cycles yet another try. no environment, 3 lights.

i tried subsurface scattering (maybe too little) and clear coat. @nathanletwory is clearcoat generally the parameter for reflection? or is the reflection only handled by the roughness i am still not entirely sure.

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Roughness is for glossy reflection. Then there is metallic to get to a metal-like reflection.

Clearcoat is for simulation some sort of finish layer on top of the material. That is why there is a clearcoat bump/normal and a clearcoat roughness channel to control the appearance of that coating layer. And as the name says: the coating is only clear.

so this is basically responsible for the reflection per se? i am a bit unsure about it because in a different renderer there are 2 different settings, one for the strength of the reflection and one for the roughness of the reflection, meaning that reflection can be increased while roughness makes the reflection scatter.

As said, roughness mainly does glossy reflection, but then there is also the metallic reflection input. If you need something to funtion like a mirror you set metallic to 1.0 with white base color. The roughness then controls the scattering of the reflection.

Here a sample with metallic and roughness with values 0, .5 and 1.0 along the shown axes.

reflections.3dm (8.9 MB)

Below a setup with metallic 100, roughnesses of 0, 50 and 100. The front row has clearcoat 100, and the backrow has clearcoat 0. Note that the front row appears to have a clean, shiny coat on top of its metallic surface. The backrow is missing that. Most clear to see in the two spheres on the right. Front sphere has environment relfection in its coat layer, the back sphere has not.

Clearcoat is like a layer of lacquer on top of the actual surface material. That lacquer can be highly polished (clearcoat roughness 0) or not. Or you can have it be slightly deformed with a normal or bump map - which is separate from the normal/bump map of the rest of the PBR.


thanks @nathan that saves at least me some more experimenting on my stone age computer, but just to resume:

it seems part of my confusion was that 0 roughness did not create any reflection at first at all and takes on my old computer very long to occur as i have found out now.

  1. the results of metallic 100 roughness and clearcoat in the lower image look very similar to the 0 roughness 0 metallic and no clearcoat setting in the first image, just that the color is darker, but that confuses me at least.

  2. so the amount of reflection is directly linked to the amount of light hitting it? or is there anything with the bounces which i have to fiddle with to get it stronger?

  3. you get additional environmental reflection with clearcoat? and would the light refract stronger/different according to the bumps/structure of the clearcoat, at least if a normal or displacement map would be used?

here i built up a scene from scratch, just one emission above. the reflections do not get stronger actually no matter how strong the light is or do i really just have to sit it out? here the light actually burns out the light reflection. in the image below i subtled it down a bit.

in the end i would like to increase the glossy reflection without having to activate metallic or clearcoat, is that a limit of the system or am i still misunderstanding it?

after furether testing it somehow does effect the reflection when i have more light coming from different angles, so i assume this is a bit of a limitation of raytraced in general, which on the other side makes it more physical i believe.

Unsaved Rhino 7 Document.3dm (6.4 MB)

oh @nathanletwory one a bug which i have noticed which drives me a bit nuts, when i change the lights, either emission strength or light strength or similar when raytraced is active it often if not always happens that it deactivates the lights and switches to default light, then i found the only way out is to switch to rendered mode for short and reinitiate raytraced viewport.

I should apologize for using mixed values. Old Rhino used often values from 0 to 100 as a percentage really. It is still visible in the texture amount fields. The PBR fields are generally 0.0 to 1.0. Old style 100 equals new style 1.0.

To understand best how roughness from the Base Color / Metallic / Roughness section (add through the Detailed settings dropdown) works have just the pbr material with white color and see the differences of roughness values 0.0, 0.5 and 1.0 (which would be in old-school speak 0, 50 and 100).

0.0 means in most cases the property is essentially disabled, 1.0 means the property is fully enabled.

Roughness means how much light is scattered from the surface. 0.0 means no scattering, 1.0 means full scattering. With a non-metallic object it is the glossy reflection. Note that glossy reflection is not the same as how a mirror works.

The following has roughness 0.0 on the left, and roughness 1.0 on the right. Neither sphere has here clearcoat, that is for both 0.0.

Now the clearcoat is essentially a separate layer from the base material. You can have the roughness of the Base Color / Metallic / Roughness section set to 1.0, yet have a nice finish on top of that. It won’t be as strong as 0.0 roughness of the base color section, but it is a bit the same - except it is on top of the base layer.

The following has on the left a sphere with roughness 0.0, clearcoat 0.0. On the right you have a sphere with roughness 1.0, clearcoat 1.0 and clearcoat roughness 0.0. You can see that the sphere on the right now has also a hint of environment reflecting in its clearcoat layer.

Now if you are looking for mirror-like reflectivity you will have to set metallic to 1.0 and ensure the base color is white. With roughness 0.0 that gives you a perfect mirror.

RH-66473 Emissive fails if moved

Sorry, I can’t help with that. But if you have been a good boy this year maybe you can ask santa claus for an upgrade.

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i am waiting for a bigger mac mini… for quite a while, want to compact my space drastically, no more laptops on the desk.