The short(est) answer is that not every desirable thing that could be
useful has been implemented yet, due to time being finite.
The slightly longer answer is that a few years ago Jonathan Brandmeyer
made a stab at implementing intensity variation for local lights, but
the API was overly technical and the effort was abandoned in the midst
of far-reaching restructuring that led to Version 5.
The deepest answer is that VPython is open source, so if you feel a
strong need for correct intensity variation (1/r^2, not 1/r^3),
consider implementing this and proposing your changes as a possible
enhancement.
Bruce Sherwood
P.S. I'll mention as an aside that the CVS repositories at
sourceforge.net, where the source for VPython is housed, have been
unavailable for some days. There was an attack on sourceforge and the
sourceforge team is working hard to make sure that none of these
repositories were corrupted.
On Thu, Feb 3, 2011 at 8:11 PM, Marcos <sta...@gm...> wrote:
> Hello,
>
> I'm rather new to VPython, using V5 w/Python3.1 and just wondering why
> I'm not seeing luminosity decay when I move a simple sphere away from
> a (local) light source. It does nicely with reflectance across the
> curved surface (decaying as the angle gets towards the tangent), but
> nothing seems to decay as it goes farther from the light source.
> Physics says it should decay at a factor r^3 (imagining photon
> emission at a constant rate, it should strike farther distances with
> less probability). If implemented, the perceptual depth-cueuing to
> the brain would be MUCH more effective than the (currently simple)
> size adjustment. But perhaps I'm just not perceiving it.(?)
>
> Am I stuck with manually decreasing the (gray-scale) color of the
> sphere as the objects moves away from the light source??
>
> Cheers and such an easy-to-use package!
>
> marcos
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