Fog makes transparency not affect shadows

[Joelaff]

In 3.03 I have some window glass that is set to affect shadows. This works great. However, when I set the fog color to anything other than pure white all of a sudden the glass casts opaque shadows.

Is there some trick for this, or is this a bug?

Giving the glass a shell modifier seems to fix it. Is that because fog requires some volume?

[Morbid Angel]

yes of course it does. Any glass/refractive object needs a volume.

[Joelaff]

I get that realism dictates you want a volume. I am just curious about the way the fog affects the shadow casting.

[Morbid Angel]

well fog tints the inner color of the glass so it darkens the light that came through. Its a bit odd to me that strong fog values like rich colors affect it that much but if you are careful you can get the fog color and the shadow still being opaque by using light values and not strong color.