Glossy material inside solid glass object

[PIXELBOX_SRO]

Hello,

so this one has been occupying my mind for quite some time.
Imagine putting a nice piece of metal inside a solid glass objects.
The result is metal object without any glossy properties.m
Even when i have the reflective refractive passes really high.
Any idea why this is?

Thanks!
M

[PIXELBOX_SRO]

Anyone? I am quite sure this has been brought up before but i cant find the right thread.

[Morbid Angel]

Yeah I can confirm this, looks like a bug?

[PIXELBOX_SRO]

thanks Dmitry!

I tried some really insane refractive and reflective bounce numbers but still get this.
its doing in bucket and progressive mode too.

ill try bidirectional path tracing but i am not sure if its still there in vray NEXT

[PIXELBOX_SRO]

Woudl anyone from Chaos please care to have a look at this problem?
Thanks!

[dgruwier]

Is it a bug though?
Here's a photo of a solid black glass sphere in an empty bowl (left), compared to one submerged in water (right):




Not particularly scientific, but you can see that even in real life, the reflections are almost entirely gone on the submerged one.
The Index of Refraction changes when you change the surrounding medium. And sure enough, if you simply crank up the IOR on your glossy object in Vray, you get the reflections back.

I'm sure there's a formula you can use to get exactly the right relative IOR to have the same apparent fresnel (Slightly more than double the original IOR seems to get close), but that is going to be an artistic choice, because I think that Vray might actually be doing things correctly here.

[PIXELBOX_SRO]

interesting! Thanks for this!
So it might be two IORs messing up then? i will have to do more tests then

[dgruwier]

I worked it out in more detail, bear with me:
Light travels at different speeds through different mediums, and the index of refraction (IOR) is simply the difference in speed between two given mediums. Speed of light in vacuum/air (roughly 300000000 m/s) divided by the speed of light of water (roughly 225000000 m/s) gives you 1.333, AKA the IOR of water.

But the difference in speed between, for example, water and glass is much lower, so the IOR between them is also going to be lower. To get that, you divide them with each other: 1.666/1.333=1.250
So if you render a reflective sphere with an 1.333 IOR inside a refractive sphere with a 1.666 IOR, then the reflective ball will look like it has an IOR of 1.250 (which seems right judging by the photo comparison, allowing for inaccuracies, exposure differences, color of the water, etc)

BUT, in the case of the render you posted, I'm assuming you used the default VRay material settings with the default IOR of 1.6000 for both spheres. 1.600/1.600=1

A reflective spere with an IOR of 1 is going to be very, very boring

[PIXELBOX_SRO]

That makes a perfect sense. I will try this right now. Thanks!

[MANUEL_MOUSIOL]

wow! I learnd something today. great info!