I would like to see support for light sources with a limited range.

Say I want do do a scene with a large number of light sources, which cast
shadows & interact with any media & surface normals, but only influence a
small area around them (faking the effect with glows or media would not do
this).

For example a suburban night scene with lots of roads & streetlights &
houses, or a large spaceship with self-illuminating lights.

If I use fade_power, I get the proper effect, but povray will perform shadow
tests on every single light source in the scene, regardless of how much
influence they have on the final colour of the rendered pixel.  This leads
to *painfully* slow render times.  Light groups can be are useful, but
aren't always suitable for the interactions I want to achieve.

What I suggest is a light source with a limited range, so that before any
shadow tests are done, povray first checks to see if each light source has
a 'limited' flag, and if it is in range of the pixel being rendered.  Any
light sources out of current range are ignored.

This would produce a visible cutoff line where each light reaches the limit
of it's 'sphere of influence' even with fade_power applied, so the effect
would need to be similar to the spotlight; with radius, falloff & tightness
parameters to smoothly fade out the light.

Does anyone else think this is worth implementing?


(PS: I am not a programmer, so I won't be writing a patch for this anytime
soon).

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