  With the legacy of Spitzer and current advances in (sub)mm astronomy, a large
number of 'transitional' disks has been identified which are believed to
contain gaps or have developped large inner holes, some filled with dust. This
may indicate that complex geometries may be a key feature in disk evolution
that has to be understood and modeled correctly. The disk around LkCa 15 is
such a disk, with a gap ranging from ~5 - 50 AU, as identified by Espaillat et
al. (2007) using 1+1D radiative transfer modelling. To fit the SED, they
propose 2 possible scenarios for the inner (<5 AU) disk - optically thick or
optically thin - and one scenario for the outer disk. We use the gapped disk of
LkCa 15 as a showcase to illustrate the importance of 2D radiative transfer in
transitional disks, by showing how the vertical dust distribution in
dust-filled inner holes determines not only the radial optical depth but also
the outer disk geometry. We use MCMax, a 2D radiative transfer code with a
self-consistent vertical structure, to model the SED. We identify two possible
geometries for the inner and outer disk, that are both different from those in
Espaillat et al. (2007). An inner disk in hydrostatic equilibrium reprocesses
enough starlight to fit the near infrared flux, but also casts a shadow on the
inner rim of the outer disk. This requires the outer disk scale height to be
large enough to rise out of the shadow. An optically thin inner disk does not
cast such a shadow, and the SED can be fitted with a smaller outer disk scale
height. For the dust in the inner regions to become optically thin however, the
scale height would have to be so much larger than its hydrostatic equilibrium
value that it effectively becomes a dust shell. It is currently unclear if a
physical mechanism exists which could provide for such a configuration.
