weird glass shading

Hi there!
I’m fairly new to blender (and blenderartists) and its rendering engine cycles, but I’m trying to model a glass (wine) bottle.
I already made up my model which is based on a spline which is then rotated via the screw modifier & subsurface.

The glass itself has just one layer of faces, as well as the fluid within (so there should be a correct refraction of the glass).

The glass material is a glass shader with IOR of 1.45 and an absorption shader from blenderdiplom (

The wine (fluid) material is similar, just the IOR is at 1.333.

The scene is lit by 3 softboxes (rectangles with emission).

If i choose the glass to be something dark, the refraction seems to fit. But as soon as I change it to something bright the refraction in the bottleneck is really weird. It’s still there, if its dark, but it isn’t as disturbing.
It seems to be in the TrandInd pass.

The scene is rendered with 700 samples on a GTX570. I’m not using a HDR map (just a grey sphere around the scene).

The model is in correct size (about 35cm high) and the studio is basically just a grey plane.

Does somebody have an explanation of what I do wrong here?

btw: I’m using a custom built 2.66 Blender Windows version. But it doesn’t work with the official one either.

Hello, danielwinter

It is strongly recommended that you model your bottle with a thickness to your glass, even if you have a volume inside a volume. You can then render your empty bottle with the correct IOR and check that the light refracts correctly. Now it really looks like a massive piece of glass. Then render the the volumetric body with the appropriate settings OUTSIDE the bottle and check the result. If everything is OK, move the fluid body inside the bottle and render the combination.
As far as I remember, Blenderdiplom states that there may be some issues with the “volume shader” when meshes are combined in certain ways.