I am using Blender 2.75 and am having trouble with an glasss shader. I apply the shader and the material underneath (an eye) appears but is dark. The glass shader is applied to the object over the eye. I have tried other posts on this forum relating to a dark glass shader but they did not work.
The screen shot below is the object with the glass shader applied. It is basically the glass shader alone. I tried reversing normals, adding a mix shader and transparancy to no avail. I am stumped …any ideas?
try turning up the diffuse bounces. i have noticed this as well, and havent fully figured it out. other then camera path factoring with a transparent shader.
When you create a glass shader in the material’s panel (as opposed to within the node editor) the default color on the glass is 236 236 236,whihc is light grey. Glass is really sensitive to it’s shade (the amount of black in it) make it pure white and you see a change.
what daedalus said about boucnes / also check your normals – glass with inverted normals is a weird dark glossy material.
And the most important, glass is treated as opaque for shadow rays!! This means that Cycles will have difficulties in finding direct light sources, and only transmission rays will let some light in (caustics). In this kind of scene, it’s advisable to make the glass totally transparent to shadow rays, either with nodes, or turning ray visibility off for shadows, in the object panel::Cycles Settings.
I am including a screen shot of my render settings. I maxed the diffuse bounce and other settings and gave the glass shader total white. Normals are correct. It improved it slightly as shown below but still dark. Very puzzling. I upped settings in my render section and tried different Light Paths using direct and limited with no change. Removed Ambient Occlusion and that had no effect. Changed lights thinking maybe the lights had something to do with it and had no affect as well.
I moved to a new layer in the same file and did a test with a simple cube and a texture applied, then added a UV Sphere and applied the glass shader and it rendered just fine. I even started a new file just to test default settings on a simple cube structure and an object in front of the cube, given a glass shader and it worked just fine. So this is a puzzle.
Secrop, I turned off ray visibility for shadows in the object panel but did not like the washout it produced. How is this done with nodes? Is it the Light Ray node that should be used for this material?
Photox, I was in the process of simplifying and packing my file when I discovered something. I was perplexed by the fact that I could create meshes and apply a glass shader with no problem. SO I simplified everything down to the eyes, thinking there was some conflict somehwre but the eyes were still dark. The eyes are a uv sphere within a uv sphere with the inner sphere containing the iris and the outer sphere being the glass shader.
Since the original did not work, I deleted everything and started with a clean UV Sphere assigned a yellow diffuse material. Then a slightly larger uv Sphere with a glass shader. As I moved the smaller yellow sphere into the larger one, the color then muted to a darker hue. If it is in front or behind there is no problem. But when the sphere goes into another, it darkens. I also created a cylinder with a glass shader and place in front. You can see the true color of the smaller uv sphere comes through. Still not sure what all this means but I found the root of the problem, a sphere within a sphere is causing this effect.
Secrop already explained why that is: The outer glass sphere is casting a shadow on the inner sphere, which will then entirely be lit by the outer sphere’s caustics.
Use a Light Path > Is Shadow Ray node as mixing factor between a Glass and a Transparent shader: This will tell Cycles to ignore the Glass shader for anything shadow related.
Thanks Ikari for explaining this further. Yes Secrop explained this earlier but I was not sure what node he was referring to. Thanks again…problem solved