Noise in glass object

[zoppo]

Your render looked sweet and was exactly what I was looking for. On close inspection I see that I gave the cloth nurbs a minus value and that is what was giving it the weird look. Changing it to a positive value made the render look more like glass.

That is to expect because the normals get messed up with a minus value. The normals of your object then stay the same but the normals of the cloth surface are reversed.

[aoktar]

Your render looked sweet and was exactly what I was looking for. On close inspection I see that I gave the cloth nurbs a minus value and that is what was giving it the weird look. Changing it to a positive value made the render look more like glass.

That is to expect because the normals get messed up with a minus value. The normals of your object then stay the same but the normals of the cloth surface are reversed.

Yes. Nothing to do else of fixing by user. This is how calculated specular refractions by renderer. It expects the correctly used face normals while enter and exit the object surfaces. Using negative values will cause inversed normals. This result is same with symmetry or negative scaled objects.