This paper offers a novel approach to the indirect photon mapping
method. The placement of photons acting as virtual light sources
is regarded as a cheap sampling scheme, allowing for the reuse of
a complete shooting path at the cost a single shadow ray. In order
to counter for its shortcomings, the variance reduction technique
called weighted importance sampling is applied. This allows for
the extension of the indirect photon mapping method for specular
settings, because the weighting function can mimic surface BRDF
characteristics disregarded by the virtual light source placement.
On the other hand, weighted importance sampling also helps to
eliminate the ``corner spikes'' caused by the fact that shooting
cannot mimic the geometric factor of the connection rays.
Advantages and problems are examined for several weighting