Sorry if this is already answered somewhere, I couldn’t find anything helpul by "Search"ing.
Say, to make a grass blade, I create a polygon, then draw a “shape” b&w texture, and apply it as Alpha modifier. The blade is then shown as needed. I add a spot light, shadows on, and the shadow is the shape of polygon (square), not the “real” rendered shape of the grass blade.
I hope this is possible.
Not that easy, you should place that texture on the spot also, make it cast a light which already has that ‘shadow mask’ make it layer only and place it on the same layer where the shadow of the grass is to be cast.
Stefano
Hmm… so if I created 50+ blades of grass like that, it becomes virtually impossible, right?
Right. Then I guess I need to make my polygon as close as possible in shape to the shape of the object, so that the shadows at least look believable 
Thanks!
By the way…
RipSting released ‘Fiber’ A grass/hair/whatever generator script… why don’t you use it?
Stefano
Do you by chance have some links for it? Or some sample pics even? Im curious.
it is virtually impossible without a raytracer.the shadow-map rendering algorithms do not take account how the texture is mapped to the object.it only calculates the geomatry of the object.so until you render your scene in a raytracer you won’t get those realistic shadows of the grass and have to use some sily tricks like s68 said.
Do a search in the python&plugins-forum for “Fiber” by author ripsting.
Thanks, Stefano, I will try to find and test this “grass” script.
I was asking more “in principle” though, and the blade of grass was an example I could come up with. Thanks for your answer, it helps me not to look further and to look for a workaround
Will there be a raytracer in Blender in future releazes, do you know?