V-Ray glas problem

#1

Hey guys,
I got a little problem with a scene I’m working on, specifically with my glass material. I’m using Vray vor C4D and the glass always comes out too dark in my scene although I’ve already deactivated volume fog in the refraction channel completely.
Here’s an image so you can see what I mean:

The glass looks good in the test scene but as soon as there’s glass behind glass in the actual scene it becomes extremely dark and I just can’t find a way to prevent this. Even if I turn my lights way up the glass on the glass table looks very dark and even the glasses on a normal surface appear too dark where the two sides overlap. Volume fog is deactivated like I said so I don’t get what’s causing this. I’m only using the refraction channel with 1.6 IOR, 100% Brightness and one glossy specular, nothing else is activated.

Thanks in advance for any suggestions!

#2

Hi, increase the reflection and refraction depth.

#3

Thanks for the tip, I just tried it and I think it helps a little but it’s still too dark. I’ve tried a number of render settings but I can’t seem to get rid of it which is really confusing since the same material looks fine in an empty scene. Here’s another test picture, I don’t even have glass underneath there and it looks even worse.

#4

I’d like to add a bit to Rens’ answer just because I feel that it’s helpful to know why a problem is occurring so that you can avoid it in the future. To calculate the refraction in the glass, a ray gets cast and gets refracted based on your IOR setting. If the trace depth is only set to 2 and it hits a 3rd surface, for example, you aren’t fully calculating what the glass should look like. Often times the result is a black or very dark glass (or whatever object you’re using).

#5

Thanks for the explanation but it seems like the problem still lies somewhere else. I set the trace depth of the glass material up to 10 for the picture in my last post and as you can see the glass is still dark. I also made sure the trace depth is not limited in the vray render settings but no luck.

#6

Is it possible that your environment is black and we are simply seeing that color in the glass?

#7

I don’t think so, it’s a room with walls on all sides and a floor and ceiling and I’m using GI for these tests so there should be light coming from all sides. Here’s another test I just rendered:

Both of the glass materials have a trace depth of 10 so that can’t be it. It’s definitley some problem with multiple layers of glass since on layer always looks fine and the more glass I got behind glass the darker it gets.

#8

Another thing that has caused me issues with glass in the past was the actual geometry or shader settings. Since I use Maya and Mental Ray, what I’m about to say may mean absolutely nothing, but perhaps it could give you some ideas.

Sometimes when using multiple layers of glass, I go into the geometry setting and make the polygons single-sided instead of double-sided. It has fixed refraction issues for me in the past.

Also, there are certain preset materials for Mental Ray that are made for glass inside vs. glass outside. These also require specific render settings.

I have no knowledge of C4D and little to no knowledge of Vray so I apologize that my suggestions may not be of any help.

#9

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