Shadow on "self illuminated" surface

[plastic_]

I'm using a satellite image as a map for ground plane.
I got other planes with normal materials, grass, asphalt, etc.
In order to not change the colors/lighting of the satellite image I excluded it from GI, which does the same thing as "self illumination" in standard materials.

Now the problem is that the shadows cast on the satellite ground plane are black, instead of semi-transparent, like the other shadows cast on normal materials.
This is because the place doesn't recieve indirect light.
Is there any way to create a material that is only visible in parts that are not hit by direct light (=shadow), so that I can layer it to get transparent shadows?

[dlparisi]

I know you said you excluded the satellite image so it doesn't change the lighting in the material but I don't understand why you'd want to do this. Don't you want the land features to bounce light according to their colors? It would also mean that shadows would be correct as well. You may need to adjust the levels on the image a little so it looks right when illuminated by the sun and sky but IMO it leads to better results.

[simmsimaging]

For camera mapped stuff like that I usually do a VrayBlendMaterial, with the base being a VrayLightMtl and the coat being a standard VrayMtl, both using the image map in the diffuse/lighting colour slots. You can adjust the brightness of the VraylightMtl to get it to match the image, and subtly blend in the basic VrayMaterial to catch some shadows. It works pretty well for me.

/b

[plastic_]

I know you said you excluded the satellite image so it doesn't change the lighting in the material but I don't understand why you'd want to do this. Don't you want the land features to bounce light according to their colors? It would also mean that shadows would be correct as well. You may need to adjust the levels on the image a little so it looks right when illuminated by the sun and sky but IMO it leads to better results.

I think it's not the right way to put another layer of shading to an already shaded image
It also means more work.
But thanks for the suggestion!

For camera mapped stuff like that I usually do a VrayBlendMaterial, with the base being a VrayLightMtl and the coat being a standard VrayMtl, both using the image map in the diffuse/lighting colour slots. You can adjust the brightness of the VraylightMtl to get it to match the image, and subtly blend in the basic VrayMaterial to catch some shadows. It works pretty well for me.

/b

That sounds like a cool trick, I'll give it a try! Thx!