<World>
   <Camera eye="0, 100, 300" look_at="0,0,0" fov="70" />
   <Option max_bounces="int 10" />
   <ShaderGroup>shader metal layer1;</ShaderGroup>
   <Quad corner="-2000,0,0" edge_x="0,0,4000" edge_y="4000,0,0" /> <!-- Botm -->

   <ShaderGroup>shader bumptest layer1;</ShaderGroup>
   <Sphere center="-60,15,120"        radius="15" />
   <Sphere center="-20,15,120"        radius="15" />
   <Sphere center=" 20,15,120"        radius="15" />
   <Sphere center=" 60,15,120"        radius="15" />

   <ShaderGroup>float eta 1.7; shader glass layer1;</ShaderGroup>
   <Sphere center="-22,40,170"        radius="15" />

   <ShaderGroup>float eta 1.1; shader glass layer1;</ShaderGroup>
   <Sphere center=" 22,40,170"        radius="15" />
   
</World>
