[Half Life]

It's a bit hard to tell exactly what is going on with your photo since it is so cropped but this happens with the Physical Sky + Sunlight.

You will not notice this if you are for instance on the interior of a scene and all the light is coming from outside because the caustics are on your side of the glass and therefor will not be any problem. However if you were on the outside looking into the same scene you would see the problem because the caustics would be on the far side of the glass and the light would have to travel back through the glass before you could see it.

Using real glass (or any dielectric) is fine if you plan for this effect and set up your lighting/shot accordingly -- but there are just some circumstances where using real Glass is just not practical because you will get back false lighting information if you don't render to very high sample levels.

Best,
Jason.

[Fernando Tella]

You can use two geometries: one with real glass hidden to GI + one with ags hidden to camera/reflections/refractions. The former gives the correct look for the glass and the latter gives a bit of shadow and reflected caustics.

[polynurb]

It's a bit hard to tell exactly what is going on with your photo since it is so cropped but this happens with the Physical Sky + Sunlight.

Hi again!

sorry for the cropping.. can't post more atm
it is actually a view from the outside..

the inside view looks like this: