Alain Martel <kua### [at] videotronca> wrote:
> > 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>}
> >
>
> The fog is more visible between the billboards because there is less of
> it. It's evaluation stops at the billboard.
>
> You may try adding hollow to those. Not sure that it'll work with fog in
> this case, but it can make a huge difference with media.
> Adding hollow MAY allow the evaluation of the fog behind the billboards.
> But, then, the fog could become more intense in those areas. Hard to tell.
>
> Try
> #declare sprite = box {<-.5,0,-.01>,<.5,1,.01> hollow} ;
> object { sprite material {M_grass_A} scale <30,40,1> translate <0,-1,0>}
> or
> #declare sprite = box {<-.5,0,-.01>,<.5,1,.01> } ;
> object { sprite material {M_grass_A} scale <30,40,1> translate
> <0,-1,0>hollow}

Thanks Alain - I gave that a shot. It didn't seem to work.

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