on Windows you can open *.pgm file with IrfanView  

model file:

width <picture_width> height <picture_height>
colors <color_gradations>
refdepth <number_of_recursive_reflection>
difdepth <number_of_recursive_diffusion>
lightdetail <dots_in_spherical_light>
difdetail <number_of_rays_in_diffusion>
k0 <0..1> k1 <0..1> k2 <0..1>

light <Intensity> <Radius>  x y z        
camera 	x y z
target 	x y z
material 	material_name reflect_factor scatter_factor color
triangle 	material_name Ax Ay Az Bx By Bz Cx Cy Cz
sphere		material_name R x y z