I am having a hard time getting specular to behave as one would expect from other engines, so I made a few test that show the problem (if there is one).
In the last image it looks like arnold is cheating somehow? The specular reflection should not be uniformly colored?
This is a bit of a continuation from this thread I started last year:
EDIT:
here the file in case anyone wants to try something:
specular publish.blend
You are right,the Fresnel equation is or should be based on view (on grazing view angle the reflection is higher vs F0 angle)
I am curios about your input with gamma setup into the specular.you can see the specular coversation here
https://docs.blender.org/manual/en/latest/render/shader_nodes/shader/principled.html
Beside the Fresnel reflection amount (in this case from the specular),the most influence is the chosen shader model (here GGX) with is microfacet roughness.
Additional,your geometric light position angle (incoming light angle) on the plane and the viewing angle (outgoing angle of reflection) light strength and size,IOR and roughness of the plane material,and of testsetup are important.
Roughness is 0, and as far as IOR goes - it only acts on transmission, so no change with 0.1 or 1000 IOR for specular / metallness
Light is 1000 Units. I guess the cutoff is dependent on that, but for the rest it should behave the same with any strength.
I too find the Specular value quite strange in Cycles. Can’t be made subtle at all, it’s completely turned off or too strong as soon as a very low value is set.
@brecht any thoughts?
I am having a hard time replicating your results. What is the size and location of the light and the camera?
here the file:
specular publish.blend
The big question is,did the Arnold shader use the same specular conversation as Cycles principled specular?
If you use this shader and specular settings then the answer is no.
https://docs.arnoldrenderer.com/display/A5AFMUG/Specular
i guess you have set the specular weight ,in your Arnold settings,in the first example post?
If i am not wrong,then the Specular weight, is how much of the reflection is mixed in. IE 0.01 are 1 % overall reflection.
This is not the same as the principled specular works,look the principled specular formula in my first post.
To simulate the behavior of the principled specular with Arnold,you have to set the weight to 1,the color to white (1,1,1) and roughness 0.
Now you have to decrease just the IOR in the Arnold specular settings.
But keep in mid that the principled uses the specular conversation.you can put in the same IOR with a little math.
here a quick IOR to specular node build.notice that IOR lower than 1 does not work.
