Trevor Quayle wrote:
>
> over distance (1/r^2), the energy stays the same but it is spread over a
> larger area:

Yes, but the observed area increases by r^2 so they cancel out.
How the energy got on or leaves the surface (direct, radiosity, transmission,
reflection) doesn't matter, the emitted energy to observer's fixed
space angle is not a function of distance.

Do your own experiment. Look at a wall from 1 m distance. Note the
brightness. Go to 3 m distance and compare the brightness. It's
the same!

A pixel gathers light from fixed space angle so the area it gathers
the energy from increases by r^2. The energy arriving at the pixel
from a fixed area on the surface decreases by 1/r^2. You don't have
to be a rocket scientist to figure this one out.

_____________
Kari Kivisalo

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