thank you, i have depended on the last updated code in the thinbasic page near the end of that page which makes the fan rotate from left to right and vice versa, it contains 3 PopMatrix ,
it appears to me that the light is shining from behind the Fan, since if we change the perl line
if ($angle_horizontal > 110)...
to
if ($angle_horizontal > 200)
the fan will show us that it is lighted from behind.
this is strange, since if we omit the body of the fan as in the file:
http://sites.google.com/site/zak31415/Home/Fan_blades.pl
it will be lighted from front