i’m just adding some little effects in a movie Recorded by myself. For this i need shadows. i’m using the “Only Shadow” Option. On the “Mirror Transp” Tab in the material section. But I’m just not able to generate smooth shadows. And I’m also not able to make shadows with a different clor than black And Also Ambient occlusion is a very difficult thing to handle with the rotoscoping technic, because somehow my shadows will always disappear if I turn Ambient occlusion on. well… any tips? and thx
To make shadows another color than black, currently the only method in Blender is to have one colored light illuminate the shadow of another light with it’s own color.
Macouno demonstrated it nicely:
https://blenderartists.org/forum/viewtopic.php?t=24776#405592
AFAIK it is not possible to get shadows generated with AO back on an OnlyShadow plane. Maybe you could use alternative methods like an icosphere with dupliverted spotlights on it’s inside?
What do you mean exactly by smooth shadows? Could you show a pic of a non-smooth and a smooth shadow?
The other answer to the colored shadows is to just make the plane’s alpha 60% or whatever you would like. This is the technique I use. I thought that I was able to get shadows with AO on only shadow material. I’ll have to go back and check.
there you are 
As you can see… if i’m not able to generate smooth shadows the artificial shadows from the starwars mech, will never really “fit” into the real movie… with normal materials, I can use arrea lights, but somehow that won’t work with shadow_only materials
Area lights work for me on OnlyShadow planes… What problem occured with you? And can’t you use Spotlights for a soft shadow?
Nice model, BTW
yeah, you’ll get shadows, but only if you use the “subtract” mode. it won’t work if you’re using the “add” mode for AO. don’t know why. it seems to me that every pixel which becomes brighter becuase of AO, the shadow disappears.
and: the coloured shadow thing doesn’t seem to work using the shadow_only method. but thx anyway…