Shader - Transmission / Refraction in Arnold compared to other render engines

[am_wilkins]

Good day,

In some recent render testing, I noticed that with matching (as far as I can see) shader and render settings across different render engines—Arnold appears to be the "odd one out" when it came to a glass shader.

Here are the render examples below.

(some render engines appear to need extra ray-depth, even though they're all set to 3 bounces)

Shader setting example:

Base / Diffuse: 0

Spec / Glossiness: 1

Transmission / Refraction: 1

IOR: 1.52

Arnold:

Arnold

Redshift:

Redshift

Karma:

Karma XPU

Vray:

Vray

Why is the Arnold result so different to all the others?

Any suggestions to get the result matching? I tried increasing IOR even more, but that seems the incorrect choice.

All the best,

amwilkins

[daniel]

Could be a ray depth issue?

[am_wilkins]

Hi,

No I don't think so—I've got all render engines set to 8 transmission / refraction depth
(Likewise, 3 diffuse and specular bounces)

Some of the engines like Redshift seem to require additional depth then those dark zones go away, but just left same settings for now.

Interesting how Karma, Vray and Redshift all look similar and Arnold is so totally different.

some setting examples:

ARNOLDREDSHIFT

ARNOLD RAYDEPTH

Thanks!

amwilkins

[daniel]

There is your issue, you limit your total ray depth to 10, hence the 8 transmission depth cant kick in.

[am_wilkins]

Hi Daniel,

Unfortunately that's not the issue... I can set "Total" super high but the render result doesn't change.

Attached below, very high depth across all settings (just to rule out any sort of ray depth problems)

arnold_render_settings_01.jpg

amwilkins

[daniel]

I guess you would need to export/provide a scene then to rule out any bugs.. if you can export an abc, I can check it in another dcc

[am_wilkins]

It's just the "Stanford Dragon"
https://casual-effects.com/data/ 

With a Arnold Standard Surface shader using they're own glass preset.

[nobody_b · Accepted solution]

i think you have double sided geo off

[am_wilkins]

Hello,

Yes!

That did the trick... I'm using Solaris—for some reason the default behavior for Arnold appears to be different to other render engines.

So I had to drop down a render geometry settings node to correct it.

double_sided_settings.jpg

Thanks for the help!

amwilkins