Objects behind glass appear too dark

Question

It's so dark that the eyes are invisible.

Blend file:

The blendfile is different to the one in the pictures. Was this done on purpose? — Chickenator, Nov 15 '15 at 08:57
Oh really? Don't remember I made any changes to this after writing the question. Does it matter much? — thododo, Nov 15 '15 at 09:31
The file's being kind of glitchy and the goggles aren't even showing up in the viewport for me. Since the material is just glass and glossy it means it's getting it's colour from it's environment so it could be the lighting that is making it look dark. Maybe try lighting up the world? — Chickenator, Nov 15 '15 at 09:46
Oh my just turn its visibilty on, man! I suppose lighting up the world wouldnt help.... — thododo, Nov 15 '15 at 09:51
The glass has no no thickness. No back faces. So the light enters the surface and for the ray the thickness is infinity. Make the goggles from 2 pieces and model the lenses properly. — Jaroslav Jerryno Novotny, Nov 15 '15 at 10:03
#Jerryno Dont ever talk something as if you are absolutely right — thododo, Nov 15 '15 at 10:27
@thododo You're the one here asking for help. Try not to be rude. — iKlsR, Nov 15 '15 at 15:19
There's something really strange about your file, I can't select the character or the goggles at all and they don't show up in the outliner. But it does look like jerryno is right, you need to give the glass some thickness. — PGmath, Nov 15 '15 at 15:49
@PGmath For me the goggles are hidden, but visible in the outliner (they're named goggles.002) with selectability is disabled (along with a number of other objects). — gandalf3, Nov 15 '15 at 23:19
@gandalf3 How do you disable selectability (I unhid everything)? — PGmath, Nov 16 '15 at 02:37
Sorry just that I was so frustrated! :( What jerrno said was definitely not the correct solution. I just didnt want to waste time on that. I just found the answer myself. Turning on reflective caustics helped. — thododo, Nov 16 '15 at 03:45
@gandalf3 Thanks, I never knew you could do that in Blender! — PGmath, Nov 16 '15 at 04:09
english is not my first language and by model "properly" I didn't meant to offend your modeling skills, I am sorry. — Jaroslav Jerryno Novotny, Nov 16 '15 at 08:18
No need for you to say sorry. I am the one who do. That's ok now — thododo, Nov 17 '15 at 01:34

score 15 · Accepted Answer · edited Apr 13 '17 at 12:57

There are several things causing this:

Lenses have no thickness (as pointed out by Jerryno)
Rendering caustics is hard

Lens geometry

In the real world the lenses are likely solid objects separate from the goggles, merely fastened into place within the goggle frames by some means.

So model virtual lenses separately and put them in the virtual goggle frames:

Start by making the goggle frames solid on their own, without any lenses:
Then model a separate lens mesh and put it in the frame. It shouldn't be connected to the frame (if you hover over it and press L, it and only it should be selected):
Ensure that the eye mesh doesn't intersect the lens:

Caustics

Even with all that, a normal glass shader will still likely look dark without lots of samples. This is due to the fact that the only way for light to get behind and illuminate the eyes is by refracting through the lenses then reflecting back out, which is a fairly unlikely path for a ray to take. See this question for more detail.

To work around this, use a setup like the one described in How to illuminate the darkness inside glass objects in Cycles?:

Thanks! How to lighten up object behind glass is definitely what I am looking for — thododo, Nov 16 '15 at 03:48
Can I ask you about your lighting? It looks sooo nice!! Couldnt think my work can look this nice — thododo, Nov 16 '15 at 04:13
@thododo The fact is I didn't touch anything. I simply enabled the existing light sources in your file; the lighting is all you :) — gandalf3, Nov 16 '15 at 06:40

Objects behind glass appear too dark

1 Answers1

Lens geometry

Caustics

Linked

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