Area lights in POVRay are geared towards *efficient* simulation of soft
shadows:
there as been a thread which stirred some discussion and ruffled some
feathers, not so long ago.

To summarize, when the lighting code encounters a light it has to do 2
things:
calculate the amount of shadowing (incident light) and the amount of
reflected (diffuse and specular) light.

POVRay calculates the the amount of shadowing using a number of shadow rays,
then it approximates the reflectance functions using a single angle of
incidence, calculating it using a light ray going from point of
intersection to (center of) light source.

While shadowing (incoming amount of light) is correct, outgoing amount of
light get increasingly incorrect as size of light increases in respect of
illuminated object.

To simulate illumination from an area light, POVRay would have to perform
the whole illumination calculation for each of the shadow rays used to test
for occlusion.

This would mean a (probably) large increase in rendering time and complexity
of the code, altough a crude hack coud involve entirely special casing area
ligths.

I'm (*very* lazingly) toying with such a hack.

Alex

P.S.: That's "lazingly" as in:
"I wouldn't hold my breath until..." or, better yet, "I wouldn't have my
worst enemy hold his breath until..." the hack is past the ideation stage.

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