refraction weirdness and noise

[Mokiki]

Hi I'm currently working on a shot for a client where I have a different spheres filled with a liquid behind each other like in a newton's cradle.
I'm getting some odd refraction behavior (color change) once the spheres visually overlap to a certain point. (attached image) Which to me doesn't look right. (The first sphere is darker because at the time of the region render it still had a darker fog color)



Here is the shader for the liquid



Second issue is the noise inside the refraction which I don't know where its coming from. I can get kinda rid of it with higher AA settings but I think there might be another issue. Because when I rendered the sphere alone (admittedly different scene) I don't get that kind of noise. (attached image)




I hope somebody can shed some light on this

[AlexP]

Is the noise issue the same as this maybe http://forums.chaosgroup.com/showthr...panes-of-glass

[Mokiki]

The noise looks similiar but my rays don't have to go through that many refractions. And if I render the spheres by themselves (no environment just domelight with a hdri for reflections) and place an object behind it I don't get any noise as well. It just happens when I place them in the room I have in. And there is no overlapping geometry or anything that could produce artifacts.

[Mokiki]

*update*
Did another test (which I should have done before sorry) but when render the glass and the liquid separately I get a clean render. As soon as I render both at the same time the noise appears again. Hmm so maybe it is similiar to the problem AlexP described.

[svetlozar.draganov]

Would it be possible to attach the scene for investigation?

[Mokiki]

Sure!

Should I send the scene to support@chaosgroup.com?

*edit*

sent the scene.

[svetlozar.draganov]

This is the same issue as AlexP mentioned.
The Min Subdiv Value of the Image Sampler should be raised a bit in order to remove that noise.
I will send you the tweaked version of the scene via email.

[Mokiki]

Thx Svetlozar for the updated scene and the additional info in the mail. Much appreciated!