I rendered an image yesterday that had Godrays peeking through Metaclouds. Bruno made a comment in which he said he could not get Godrays to shine through Metaclouds before, so I thought I might share the things I discovered to get that effect.

The clouds:

You cannot get Godrays with a single Metacloud, at least I couldn't. Just as it is the case with a cloud layer you need a hole with more ore less sharp edges in your metacloud where the sun can peek through. So either you arrange the spheres in the metacloud so that you get a hole inside your cloud or you combine several Metaclouds to one big cloud with a small hole. I found the second method to be far easier.

The clouds themselves have to be very dense, but not extremly. I used a value about 60 % density. The clouds MUST cast shadows and MUST be self-shadowing. The edges don't have to be razor-sharp, but too much fuzzy detail at the edges won't work either. 80 % detail amount worked pretty good for me with a medium size scaling.

The Godray intensity slider had no effect for me whatsoever.

The atmosphere:

1. Turn on the godray option.

2. Increase the Aerial perspective at least to a value between 20 and 30, so that you get more haze in the distance. Apart from that for me it wasn't necessary to tamper with the haze or fog sliders.

3. Increase the glow intensity to a fairly high level, because since the sky is not covered by clouds apart from your Metaclouds, the rays will be hardly visible with a glow amount of just 1 %.  Since your sky will be overexposed by now increase the scattering anisotropy so that only a small area around the sun is glowing. I used a glow intensity of 56 % and a scattering amount of 0.81.

4. Make the sunlight VOLUMETRIC!!! If it's not volumetric you won't get any rays at all shining through your metaclouds. That was the one thing I spent a lot of time figuring out.

5. Place the sun in the hole of your cloud and hopefully you should see some godrays peeking through.

Of course this is just what I used and I'm sure the visibility of the rays also depends on the cloud shape and the other atmosphere settings like decay amount and so on, so you might need to experiment. But maybe these settings are a good starting point :-).

Thanks a bunch, Daniel.

Nice Daniel, tolles Bild mit den Metawolken!

By the way, have you found a way to get sharp shadow edges for Vue clouds? I find that making the Vue clouds look very unrealistic.

Yeah! Thanks! I'm really liking this info!

For the most realistic effect if it's better to use alot of smaller metaclouds or fewer larger metaclouds?