After taking some time off from POV, I'm ready to tackle a few new scenes I have
in mind. One involves a landscape with some foreground vegetation. I started
collecting some 2D sprite images of moss, grasses, and weeds thinking that I
could populate the ground with them. I've run into a problem with the
transparent portion of the png when turning on fog. The fog is tinting the
billboard shape. I've removed the finish and have tried a variety of things in
the shader with no success. I can fall back on 3D models if I can't get the
sprites to work.  Below is what I used to texture this example. I understand
that the bump statement will not have much of an effect without a finish. Any
help would be appreciated.
Thanks,
Mike.

#declare imgDiffuse = "plants/grass_A.png"
#declare imgBump    = "plants/grass_A.png"

#declare M_grass_A =
material {
    texture {
       pigment {
            image_map {
                png imgDiffuse premultiplied 0 gamma 2.2
                map_type 0
                interpolate 4
                }
      }
    normal  {
        bump_map {
            png imgBump premultiplied 0 gamma 2.2
            map_type 0
            interpolate 4

        }
        bump_size 5
    }
    finish {
        phong 0
        phong_size 0
        ambient 0
        }
    }
    scale <1,1,1>
    translate <-.5,0,0>
}

#declare sprite = box {<-.5,0,-.01>,<.5,1,.01> } ;
object { sprite material {M_grass_A} scale <30,40,1> translate <0,-1,0>}

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