I have some questions about light groups.

In this scene I have a white sphere iluminated by red light, both forming a
light group. I also have a white light iluminating the global scene. The
plane is correctly unnaffected by the red light: the sphere casts no shadow
resulting from this red light. Now here is what seems odd to me. If the
white light is, in this case, the global light, and I have the command
global_lights set to off, how come the white light still interacts with the
sphere, causing it to cast a shadow on the plane? Is this really the
intended behaviour? If so, is there a reason for it being so?

Ruy

========================

Here is the code:

#declare RedLight = light_source {
  <-5,5,-5>
  rgb <1,0,0>
}

camera{
  location <0, 5, -10>
  look_at 0
}

light_source { y*100 rgb 1 }

light_group {
  light_source {RedLight}
  sphere {0,1 pigment {rgb 1}}
  global_lights on
}

plane { y, -2 pigment { rgb 1 } }

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