Woodie, I'm a bit of a noob, so my statements could be erroneous. Feel free to check the .blend file. Thanks for your help.

Could you post the material files?

Thanks zsouthboy, but I get the same result with or without the plane.

Not exactly sure what you mean by "welded", but I've removed all double vertices, and the mesh is solid (no holes). Thanks for the reply.

Ha! I didn't even see that. Now I kinda like my render...

But seriously, I just want plane-ole liquid.

Thanks palawat. I used this to begin with, and the results were fine when looking at the volume of liquid from the side (like the render in the manual). However, it's the top of the liquid that's giving me problems. As the partial render shows above, there are strange concentric around the outside, ...

Yeah, this isn't my actual project, just a small example of the problem. Fewer polygons causes the same error. It seems to be the shape of the mesh that's causing the problem.

The specular material is set to transparent.

Thanks, and if you get a chance to take a closer look, I'd appreciate it.

I'm new to the 3D modeling world, and just started working with blender and indigo at the beginning of this month. Anyway, I was trying to model a glass of wine (since everyone seems to do that as a beginner exercise), and ran into problems when trying to "fill the glass with wine". The glass itself...

Where do you set "UV-Set"? I can't find this anywhere in the manual or web. I see UV Texture which is named UVTex by default, but not UVSet.