<scene>

  <image>1 1</image>

  <sampler type="JitteredSampler">
    <numSamplesU>1000</numSamplesU>
    <numSamplesV>1000</numSamplesV>
  </sampler>

  <renderer type="DirectOnlyMediumRenderer">
    <directIlluminator type="LuminairesIlluminator" />
  </renderer>

  <!-- camera at 60 degrees -->
  <camera>
    <eye>-866 500 0</eye>
    <target>0 0 0</target>
    <up>0 1 0</up>
    <yFOV>0.01</yFOV>
  </camera>

  <!-- light source producing normal irradiance pi -->
  <surface type="Sphere">
    <material type="LambertianEmitter">
      <radiance>1000000 1000000 1000000</radiance>
    </material>
    <center>866 500 0</center>
    <radius>1</radius>
  </surface>

  <!-- Lambertian surface to confirm irradiance -->
  <!--surface type="Triangle">
    <material name="grey" type="Homogeneous">
      <brdf type="Lambertian">
	<reflectance>1 1 1</reflectance>
      </brdf>
    </material>
    <v0>   0   0  500.0</v0>
    <v1> 433.0 0 -250.0</v1>
    <v2>-433.0 0 -250.0</v2>
  </surface-->

  <!--
    This is a slab of medium one unit thick.  By a simple
    derivation from Chandrasekhar (you can find it in Hanrahan
    & Krueger 93) the diffuse reflectance of such a layer,
    considering only single scattering, is:

    (al/4pi) (1 - exp(-sg_t d(1/mu_i + 1/mu_r))) / (mu_i + mu_r)
   
    where al is the albedo; sg_t is the attenuation coeff; d is
    the layer thickness; mu_{i,r} are the incident and exitant
    cosines.  For this setup we have  mu_i = mu_r = 0.5 and d = 1.
    This leads to reflectance 0.0550463, radiance 0.0864665.
  -->

  <medium type="HomogeneousMedium">
    <minPt>-100 -1 -100</minPt>
    <maxPt>100 0 100</maxPt>
    <absorptionCoefficient>0.1 0.1 0.1</absorptionCoefficient>
    <scatteringCoefficient>0.4 0.4 0.4</scatteringCoefficient>
  </medium>
</scene>
