I am having a problem with **refraction** in Carrara so I was wondering if anyone has any suggestions. 

I am trying to render a glass sphere, with a small thickness added, that has a plane with an 
image on it, placed inside the sphere. I've tried several different file formats to map the image
on the plane, but the alpha is refracting, causing it to be visible. (see image)

I also made sure reflections and highlights are turned off in the shader, and it still isn't working.

Any help would be greatly appreciated!

Atually, I don't think it is refraction, but transparancy...

Do you have the 'light through transparancy' box ticked?
Are you rendering with GI or IL? There is also a second 'Light through transparancy'

And in the shader there is a box that reads 'no light interaction when fully transparant' when you select the top shader, next to the transparancy channel.

Maybe one of those needs ticking?

Hi Discoseven, Alpha planes and refraction do not play well together. The only work-around I can suggest is to exaggerate the reflection and transparency behaviours using some extra shading tools like DCG's Fake Fresnel (in Shader Ops) or Shoestring Shaders Easy Fresnel (part of the whole SS packge). The image above uses no refraction, just Easy Fresnel in the reflection and transparency channels. Sometimes we just have to lead the viewers eyes to look at other things... ;) Mark

Mark, I have a burning question, is the fresnel setting in the C5Pro reflection and transparancy setting not usefull for this? I understand you still use third party fresnel components?

(I didn't know there was a special thing with refraction...)

I saw you use the ShaderOps fresnel earler, it catched my eye that time too.

Hi Hoof, The Carrara fresnel is very nice but it does require use of refraction (this is stated adjacent to the fresnel checkbox for transparency and reflection). So, if you can't use refraction, then you also can't benefit from the Carrara built-in fresnel effect either. That's the reason I'm suggesting the other tools. They will allow the benefits of fresnel effects in both transparency and reflection without requiring refraction. Mark

Ah. So now I now why that fresnel effect sometimes doesn't seem to have much of an effect... An empty refraction channel. An important lesson I learned today! Thanks!

(never read that sentence about refraction right to the end, I just discovered)

As an aside, the other reason I'll not use the Carrara built in refraction is shown above. Even though this globe has thickness and is hollow in the middle, Carrara renders it as a solid, like a marble. Now we've all seen big fish bowls or terrariums with plants in them and know that the distortion is only on the sides of the globe. Consequently, I just eliminate the refraction and engage the other features of fresnel with the tools described above. Personal preference. :)

Thanks for the help Hoof and Mark - 

To answer your questions Hoof, I had tried everything you mentioned, with no sucess. I will try Mark's suggestions and see if that will give me an acceptable render.  I'll let you know how it goes. 

P.S. Just so you know, I'm not making snow globes :)

if the inner and outer surfaces of a glass sphere are concentric, then the sphere can't act as a diverging or converging lens for anything inside it, as mark noted. the image in msg 3 looks pretty good IMVHO.

Hmmm, very interesting! This answered a question I had about Carrara's built-in fresnel settings.