The area_illumination option in POV-Ray 3.7 has given me the opportunity 
to see how area_light distributes its points.  File 
area_illumination.jpg shows a simple 5x5 grid, scaled to a 2x2 fill 
area.  Fair enough.

But is it?

The points extend all the way to the edge of the fill area.  This has 
less than ideal consequences.  File area_light_jitter1.jpg shows a 
jittered 5x5 grid.  The
light extends beyond the grid area.  This is easy to correct in SDL, 
however, using the formula:
    axis_length * (number_of_points - 1) / number_of_points

Less easy to work around is the circular pattern.  File 
circular_light05.jpg shows the 5x5 circular pattern.  The points are not 
evenly spaced.  The 17x17 pattern in circular_light17.jpg shows clearly 
the uneven lighting effect, although I don't know how much visual impact 
this has on a scene.

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Download 'area_illumination.jpg' (12 KB) Download 'area_light_jitter1.jpg' (43 KB) Download 'circular_light05.jpg' (12 KB) Download 'circular_light17.jpg' (16 KB)

Preview of image 'area_illumination.jpg'

Preview of image 'area_light_jitter1.jpg'

Preview of image 'circular_light05.jpg'

Preview of image 'circular_light17.jpg'