Specular Reflection Wrong?

[treddie]

Maybe it's just me, but the "4" and the "5" reflections appear way too dark to me. The "3" seems correct.

This is using v1.36

[TRRazor]

If you're looking at the reflection of "3" you'll surely have noted, that it is "hovering" over a brighter "background" than "4" and "5". Since those two are in the more shadowy area cast by the clocks housing the reflection is also darker.

Not a problem with Octane but actually a problem with reality ^^.

Try readjusting the light a notch down (if that is a possibility) so the reflections of 4 and 5 will be over the "non-shadow"-area of the face.

Hope this helps

[treddie]

TRRazor, I'm not so sure. Check out this comparison between the darkness behind the refracted 3 and 4. They are virtually identical.

Refracted 3 and 4.jpg (85.95 KiB) Viewed 3003 times

[krzychuc4d]

It really looks bad.

I always struggle with glass in Octane.
Sometimes Octane captures wrong reflection like yours and other time
glass looks too dark even if environment is bright.
Octane sometimes should be more "idiot proof"

My suggestion is to select glass object and change it shading angle to very low value,
I'm Cinema4D user and I'm not sure how this works in other software than cinema

[treddie]

I'm C4D, too, but I use Octane standalone. I'll experiment with what you suggested when I can free up my GPUs, and see what happens.

Are you referring to Phong shading angle?

[boris]

for me this looks more like a projection if I consider the positions of the numbers on the glass.
anyway, why should there be a reflection on the glass of something behind it?
sorry maybe I am totally wrong but I just starred at your image for 3 minutes and just did not understood it.
have you checked normals?
I sometimes get confusing results with glass having flipped normals after attaching mirrored geometry to a 3ds max poly (annoying bug).

[treddie]

Yah, I would expect double reflections of objects in front of the glass but not behind it...I have a glass table here in front of me and there are absolutely no double reflections for anything I place right underneath it, at any incidence angle.

My normals are correct. Just checked.

[cakeller98]

Can you export the model to octane, and post it? or just export the relevant snippet?

[treddie]

Come to think of it, I think the reflection of something under the glass is theoretically correct according to the Law of Reflection, but I think it is generally very very subtle. I think the idea behind it is that the image of those numbers is cast up onto the first and second surfaces of the glass, getting partially reflected and refracted both times to a degree depending on the incidence angle. So the image of the numbers reflecting off the first surface simply bounce back down and attenuate very quickly. But that portion of those very same rays that make it through the first surface of glass then collide with the second surface of glass and again, part is reflected back into the glass and part passes through it to our eyes. So now again, the very weak portion of the light that reflected off the second surface now both partially bounces off the first surface again and passes through the second surface towards our eyes as the second image of the numbers, with the remainder passing through the first surface back towards the bottom. So, light is reflecting back and forth zillions of times, getting weaker with each pass. So we would be lucky to catch the first reflection off the first glass surface, let alone any further reflections.

So I think the problem in Octane is that those glass reflections of what is underneath the glass are WAY too pronounced. My feeling is that the light rays that make the reflections aren't decaying nearly as rapidly as they should.

[Olitech]

Come to think of it, I think the reflection of something under the glass is theoretically correct according to the Law of Reflection, but I think it is generally very very subtle. I think the idea behind it is that the image of those numbers is cast up onto the first and second surfaces of the glass, getting partially reflected and refracted both times to a degree depending on the incidence angle. So the image of the numbers reflecting off the first surface simply bounce back down and attenuate very quickly. But that portion of those very same rays that make it through the first surface of glass then collide with the second surface of glass and again, part is reflected back into the glass and part passes through it to our eyes. So now again, the very weak portion of the light that reflected off the second surface now both partially bounces off the first surface again and passes through the second surface towards our eyes as the second image of the numbers, with the remainder passing through the first surface back towards the bottom. So, light is reflecting back and forth zillions of times, getting weaker with each pass. So we would be lucky to catch the first reflection off the first glass surface, let alone any further reflections.

So I think the problem in Octane is that those glass reflections of what is underneath the glass are WAY too pronounced. My feeling is that the light rays that make the reflections aren't decaying nearly as rapidly as they should.

Interesting. Do you think this is because Octane glass does not contain a fresnel falloff?

I've also noticed that if I reduce the 'Opacity' parameter on specular materials, I keep getting double reflections...

Best,
O