From PixieWiki

[edit] Soft Raytraced Shadows

In order to have soft raytraced shadows, you can either use the shadow or transmission calls with blur parameter set to something other than 0 (default).

For example, if you change (in shadowdistant.sl)

vis = (1 - shadow(shadowname,Ps));

with

vis = (1 - shadow(shadowname,Ps,"blur",0.1));

you should get the following picture:

A blur value 1 means that the light source is hemispherical. The blur value 0 means the light source is pure directional.

Notice the noisy shadow penumbra because the default number of samples for shadow call is 1.

If we use the following line:

vis = (1 - shadow(shadowname,Ps,"blur",0.1,"samples",50));

we get the following picture which looks much better:

[edit] Soft Transmission Shadows

You can use the transmission function in a shader to get soft shadows without using shadow(). I got the below shader from the sig03.course09.pdf and the rib from the point based occlusion example.

The Shader:

light transmissionspot (
       float intensity=1, beamdistribution=2;
       color lightcolor = 1;
       point from = point "shader" (0,0,0);
       point to = point "shader" (0,0,1);
       float coneangle=radians(30), conedeltaangle=radians(5);
       float samples=1, blur=0, bias = -1;)
{
       uniform vector A = (to - from) / length(to - from);
       uniform float cosoutside= cos(coneangle), cosinside = cos(coneangle-conedeltaangle);
       illuminate( from, A, coneangle ) {
               float cosangle = L.A / length(L);
               color atten = pow(cosangle, beamdistribution) / (L.L);
               atten *= smoothstep( cosoutside, cosinside, cosangle );
               atten *= transmission(Ps, from, "samples", samples, "samplecone", blur, "bias", bias);
               Cl = atten * intensity * lightcolor;
       }
}

The Rib:

FrameBegin 1
       Format 400 300 1
       PixelSamples 4 4
       ShadingInterpolation "smooth"
       Display "transmission spot" "framebuffer" "rgba"
       Display "+transmission.png" "file" "rgba"
       Projection "perspective" "fov" 22
       Translate 0 -0.5 8
       Rotate -40 1 0 0
       Rotate -20 0 1 0

       WorldBegin
               LightSource "transmissionspot" 1 "intensity" 200.0 "lightcolor" [1.0 1.0 1.0]
               "coneangle" 40 "from" [1 10 5] "to" [0 0 0] "samples" 32 "blur" 0.1 "bias" 0.01
               Illuminate 1 1

               Attribute "visibility" "int transmission" [1] # use this to turn transmission on and off

               Surface "plastic"

               # Ground plane
               AttributeBegin
                       Color 1 1 1
                       Polygon "P" [ -5 0 5 5 0 5 5 0 -5 -5 0 -5 ]
               AttributeEnd

               # Sphere
               AttributeBegin
                       Color 1 1 1
                       Translate -0.7 0.5 0
                       Sphere 0.5 -0.5 0.5 360
               AttributeEnd

               # Box
               AttributeBegin
                       Color 1 1 1
                       Translate 0.3 0.01 0
                       Rotate -30 0 1 0
                       Polygon "P" [ 0 0 0 0 0 1 0 1 1 0 1 0 ] # left side
                       Polygon "P" [ 1 1 0 1 1 1 1 0 1 1 0 0 ] # right side
                       Polygon "P" [ 0 1 0 1 1 0 1 0 0 0 0 0 ] # front side
                       Polygon "P" [ 0 0 1 1 0 1 1 1 1 0 1 1 ] # back side
                       Polygon "P" [ 0 1 1 1 1 1 1 1 0 0 1 0 ] # top
               AttributeEnd

       WorldEnd
FrameEnd

[edit] Stained Glass Shadows

Using the same transmissionspot shader from the 'Soft Transmission Shadows' tutorial, and modifing the rib a little, we can use transmission to create the "stained glass" shadow effect. Use the below shader that I got from sig03.course09.pdf.

The Shader:

surface stainedglass ( string texturename = "" )
{
   /* a simplistic stainedglass effect,
    * note the decoupling of Oi and Ci
    */
   color x = color texture(texturename);
   Oi = 1 - x;
   Ci = x * x; /* pleasantly saturated */
}

Use this image:

Media:Pixie_semi-transparent.tiff

Then use texmake to create the tx file:

texmake Pixie_semi-transparent.tiff Pixie_semi-transparent.tx

If you use your own image, be sure to add an alpha channel and set it to the amount of transparency you want.

The Modified Rib:

FrameBegin 1
       Format 400 300 1
       PixelSamples 4 4
       ShadingInterpolation "smooth"
       Display "stained glass" "framebuffer" "rgb"
       Display "+stainedglass.jpg" "file" "rgb"
       Projection "perspective" "fov" 22
       Translate 0 -0.6 8.5
       Rotate -35 1 0 0
       Rotate 170 0 1 0

       WorldBegin
               LightSource "transmissionspot" 1 "intensity" 200.0 "lightcolor" [1.0 1.0 1.0]
               "coneangle" 40 "from" [1 10 5] "to" [0 0 0] "samples" 64 "blur" 0.02 "bias" 0.01
               Illuminate 1 1

               Attribute "visibility" "int transmission" [1] # use this to turn transmission on and off

                Surface "plastic"

               # Ground plane
               AttributeBegin
                       Color 1 1 1
                       Polygon "P" [ -10 0 10 10 0 10 10 0 -10 -10 0 -10 ]
               AttributeEnd

               # Sphere
               AttributeBegin
                       Color 1 1 1
                       Translate -0.7 0.5 0
                       Sphere 0.5 -0.5 0.5 360
               AttributeEnd

              # Box
               AttributeBegin
                       Color 1 1 1
                       Translate 0.3 0.01 0
                       Rotate -30 0 1 0
                       Polygon "P" [ 0 0 0 0 0 1 0 1 1 0 1 0 ] # left side
                       Polygon "P" [ 1 1 0 1 1 1 1 0 1 1 0 0 ] # right side
                       Polygon "P" [ 0 1 0 1 1 0 1 0 0 0 0 0 ] # front side
                       Polygon "P" [ 0 0 1 1 0 1 1 1 1 0 1 1 ] # back side
                       Polygon "P" [ 0 1 1 1 1 1 1 1 0 0 1 0 ] # top
               AttributeEnd

              # Image Panel
               AttributeBegin
                       # If you use "primitive for the last option on the below command
                       # it will give you a solid shadow from the geometry.
                       # Using "shader" will let the light pass through and color the
                       # objects below
                       Attribute "shade" "transmissionhitmode" "shader"
                       Surface "stainedglass" "texturename" "Pixie_semi-transparent.tx"
                       Translate 0 1.5 0
                       Rotate -30 0 1 0
                       Scale 2 1 2
                       Polygon "P" [ 0 1 1 1 1 1 1 1 0 0 1 0 ] "st" [ 1 0 1 1 0 1 0 0 ]
              AttributeEnd

       WorldEnd
FrameEnd