Hi.

This problem may have been addressed before...

Anyway, I have discovered a quirky thing I haven't noticed before about
area lights in POV.

It seems when using liht fading, the brightest spot, from where the
attenuation starts is the center of the area_light, i.e. the
illumination is not distributed evenly across the surface of the
area_light source.

This is especially anoying when using higly elongated light sources like
neon tubes with light fading - there is a bright spot of liht at the
nearby wall around the center of the tube, which does not look very
realistic.

I have included an example scene which demonstrates this well (uncomment
the media if U got the time):

/BEGIN SCENE/

camera {location <7,0,-10> look_at <0,0,0>}

light_source {<0,0,0> rgb <1,1,1>
             area_light y*5, x, 5, 2 adaptive 1 jitter
             fade_distance 2 fade_power 2}
             
//media {scattering {1 rgb .1}}
             
plane {z, 1 pigment {rgb .8} finish {ambient .2 diffuse .6} hollow}

polygon {4, <-.5, -2.5, 0>, <.5, -2.5, 0>, <.5, 2.5, 0>, <-.5, 2.5, 0>
         pigment {rgb 1} finish {ambient 1 diffuse 0} no_shadow}

/END SCENE/

Is this inherent in the way POV simulates area lights?
Is there a workaround for this problem?


Thanks.

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Heh heh just what I was going to ask last night at 1:00 a.m. ( but I
postponed it until 5 a.m. since I went to sleep and I use a free i-net
account from 4 a.m. to 8 a.m. :-(

Seriously, I wanted to place several neon bulbs on the left wall of a tunnel
I am making. Did not work with area lights. Here's a workaround of the
problem (no adaptive 0 of course). Fix to suit your needs (use as an
area_light, spherical_light, my_girlfrend_shaped_light etc.)

Hope this helps.

--Peter

pet### [at] usanet

#declare Lamps=5
#declare Bulbs=5

#while (dummy<Lamps)
  #declare dummy1 = -div(Bulbs,2)
  #while (dummy1<=div(Bulbs,2))
    light_source
    { <-4.25,4.5,dummy*15+dummy1*3/Bulbs> color Gray50/Bulbs
      fade_distance 4
      fade_power 2.25 // not what you'll see in real life, but who cares?
    }
    #declare dummy1=dummy1+1
  #end
  #declare dummy=dummy+1
#end

Margus Ramst wrote in message <35D### [at] peakeduee>...
>Hi.
>
>This problem may have been addressed before...
>
>Anyway, I have discovered a quirky thing I haven't noticed before about
>area lights in POV.
>
>It seems when using liht fading, the brightest spot, from where the
>attenuation starts is the center of the area_light, i.e. the
>illumination is not distributed evenly across the surface of the
>area_light source.
>
>This is especially anoying when using higly elongated light sources like
>neon tubes with light fading - there is a bright spot of liht at the
>nearby wall around the center of the tube, which does not look very
>realistic.
>
>I have included an example scene which demonstrates this well (uncomment
>the media if U got the time):
>
>/BEGIN SCENE/
>
>camera {location <7,0,-10> look_at <0,0,0>}
>
>light_source {<0,0,0> rgb <1,1,1>
>             area_light y*5, x, 5, 2 adaptive 1 jitter
>             fade_distance 2 fade_power 2}
>
>//media {scattering {1 rgb .1}}
>
>plane {z, 1 pigment {rgb .8} finish {ambient .2 diffuse .6} hollow}
>
>polygon {4, <-.5, -2.5, 0>, <.5, -2.5, 0>, <.5, 2.5, 0>, <-.5, 2.5, 0>
>         pigment {rgb 1} finish {ambient 1 diffuse 0} no_shadow}
>
>/END SCENE/
>
>Is this inherent in the way POV simulates area lights?
>Is there a workaround for this problem?
>
>
>Thanks.

Post a reply to this message