Color Glass Cycles vs Arnold


(czesiek) #1

Hi,
I’m trying to recreate color glass shader that I made in Maya/Arnold before, scenes are not identical since my Maya trial expired i couldnt export the scene but I made it as close as possible.
Questions:

  1. How to get rid of fireflies?
  2. Why in Arnold shadow is transparent on the edges and in Cycles it’s sharp?
  3. Why in Cycles I have specular highlights when specular is off?
  4. How to get similar transition scattering (look at the wings) ?

blend file:
http://www.rapidshare.com.cn/PXQc74H


(ajm) #2
  1. More samples and a bit of clamping (but high values so you don’t loose a whole lot of dynamic range) will get rid of fireflies. It’s a result of specular and diffuse objects with bright light sources being in close proximity to one another.
  2. Different calculations? Thin glass material in Arnold? I don’t know.
  3. Specular in principled shaders is more like an approximation of fresnel, not how specular a surface is. That is determined by roughness.
  4. You’re doing it by using the volume absorption input, but can be calculated differently in different renderers. Also, having the model built to scale goes a long way.

Another tip is that for a scene like this, you will rarely need 128 bounces of anything. It’s an open stage so there is a good chance that your diffuse bounces will expire at 1 or 2 bounces. The higher bounces, like around 6 to 12 should be used for glossy and transmission for this model. I don’t use the square samples, and rather type in a hard value. 1024 gave a good result, of you want you can use a bit less and activate denoising, but this can be problematic for materials like this.


(petitwilly) #3

helo,
I did the test with version 2.8 of Blender but it must be identical in version 2.79.
you can use the attached file with version 2.8 and copy the connections of the nodes in the 2.79 version.

Blend File

Test__Volume


(petitwilly) #4

Hello,
until I see the version Blender 2.79, here is a screenshot of the 2.80 nodes.
as soon as possible I will join the blend file of 2.79.


(czesiek) #5

thanks a lot man


(czesiek) #6

Principled and Glass without Volume gives identical effects
With Volume shader they are both bit different. Why? Shouldn’t Principled work the same?


(petitwilly) #7

hello,
on my config the results are pretty similar.
maybe it comes from your configuration settings.

Glass :

Principled :

Glass Customized :

Render Glass Custom :
Glass

Blend File 2.79 : trans.blend (907.0 KB)


(czesiek) #8

Nope :slight_smile: My Volume is a Mix of Absorbtion and Scatter, try this.
Also I already found out that Principled is bit different than Glass if you give them roughness 0.2 for example, they will render bit differently.


(petitwilly) #9

Of course these shaders are different. principled respects the principle of energy conservation, it is not only an encapsulation of Diffuse, Glossy and Glass Shaders.
there are many other differences.
From my experience the Add Shaders has always worked better than the Mix Shaders. for translucent glass…
I’ll try the Mix Shaders and I’ll let you know about my tests …


(czesiek) #10

That’s what i thought, now I know it’s not like that too :slight_smile:
I read abolut Add Shaders they may produce undrealistic result (for example they may reflect more light than they should) and it’s recommended to use Mix instead.


(petitwilly) #11

Here is my test with the Mix Shader :

Glass :

Principled :

Blend File with Mix : trans_mix.blend (860.2 KB)


(czesiek) #12

:open_mouth:


(czesiek) #13

I know, I had GGX in Principled while in Glass i had Backmann :tired_face: