[Sorin]

I am trying to render planet Earth for a personal project and I am having a really weird problem rendering clouds over another layer.

In the first render it's just the cloud layer with a smooth transition into the shadow area:


In the second render I added a simple standard material under it. Now, the cloud layer it's just sliced with no traces in the shadow area.


Cloud material:


If you have any suggestions, please, let me know.

[arttorney]

Do you have only one light? The difference between the first one and the second one might be because the globe is now blocking light to the clouds on the left that were previously lit by light traveling through where the globe now is. I know putting a billion little lights of various colors all around the scene is too labor intensive. Try giving the clouds 5 or 10 percent self illumination of an unsaturated ultramarine color and see what it looks like. Don't put too much, or they will be casting obvious lights onto the surface of the globe and it will be weird looking. If it's not too obvious, then later it can probably get lost in a detailed globe surface and look like city lights or something. If you do this, I would try some global lighting style like Photon Mapping Final Gather that will allow the clouds to light each other a little bit (hopefully without being as much of a drain on the system as Photon Mapping Direct).

Another idea might be to have the simple globe itself send out a wee bit of light.

[Sorin]

Well, I was more interested in what caused the problem than in the solution, and your explanation might be one of the reasons it renders that way. I added a small amount of self illumination, but it didn't solved the problem, the bump is still sliced. So.. I thought is better to avoid the problem by having the best of both worlds. I added 2 lights both in the same spot, one for each geosphere. In the light properties that affect the terrain I excluded the clouds from casting shadows and vice versa. So, now the clouds retain the detail I was trying to get.

3rd render with one light for both objects & self illumination (the clouds show up on the dark side but still no fade in the bump):


4th render with one light for each geosphere: