Andrey,

I gave it a quick look and I have something simple that looks like it works.

Try this:

#version 3.8;

global_settings {assumed_gamma 1.0}
#include "colors.inc"
//#include "Metals.inc"
//#include "textures.inc"

#declare Height = 10;
#declare Radius = 10;
#declare Falloff = 40;

#if (Falloff < Radius)
 #error "Falloff value must always be larger than the radius value!"
#end

camera {
   location  <0.0, Height, 0.0>
   look_at   <0.0, 0.0,  0.0>
   up y
   right     x*image_width/image_height
}

//#declare Mirror =  box {0, 1 translate -0.5 scale <10, 10, 0.1> texture
{Polished_Chrome} translate z*10}



// create a point "spotlight" (conical directed) light source
light_source {
   <0, 10, 0>
   color rgb <1,1,1>
   spotlight
   point_at <0, 0, 0>
   radius Radius   // angle of the fully illuminated cone.
   tightness 60   // determines the rate of the light falloff
   falloff Falloff   // angle of the umbra cone where the light falls off to
darkness
}

plane {y, 0 pigment {White} finish {diffuse 1}}

// tan theta = WIDTH/adjacent
#declare HalfWidth1 = tan(radians(Radius))*Height/2;
#declare HalfWidth2 = tan(radians(Falloff))*Height/2;
#declare Line = 0.015;

torus {HalfWidth1, Line pigment {Red} finish {emission 1}}
torus {HalfWidth2, Line pigment {Green} finish {emission 1}}


Bill

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