This may be what you were discussing regarding "soft shadows", but is that refuring to the UMBRA, PENUMBRA effect? Since the "sun" in a mission isn't a point-source light, then it will cast a dark shadow that's smaller than the object casting it, with a lighter shadow around it, which is much larger than the object casting it. The farther away from the object, the smaller the dark shadow is, and the larger the grey shadow is.
On another note, will shadows be feasable in a nebular environment, where gas behind an object (in relation to the sun) is not illuminated?
Later!