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Black background, Octane Specular = white object?

Posted: Wed Jul 06, 2022 7:23 am
by ycmitch
I have a black background, and assigned 'Octane Specular' to a sphere. My assumption here is that it's entirely transparent like glass.
Yet, when I render it's entirely white.

Is this assumed behaviour? Where does the white come from?

Image

Re: Black background, Octane Specular = white object?

Posted: Wed Jul 06, 2022 10:47 am
by elsksa
Hi,
It would look as expected with higher sub-division (3, using the Sphere Primitive Geometry).
octane_29PxlJNy7X.jpg
Without high enough sub-division, the geometry will feature clearly visible "faces" that will bend the light direction as it is a specular (glass) material.

Side note: it is strongly recommended to set the "BRDF Model" to GGX Energy Preserving.

Re: Black background, Octane Specular = white object?

Posted: Thu Jul 07, 2022 8:14 am
by bepeg4d
Hi ycmitch,
the white comes from the default Environment that is set to light gray.
If there is nothing else in the scene, there is nothing to reflect refract for the Specular material.
Try to add an HDRI Environment to have a non constant Environment to reflect refract:
0E232D4C-3D23-4CA0-83E3-85264E1C0108.jpeg
ciao,
Beppe