  This paper discusses the properties of the inner puffed-up rim which forms in
circumstellar disks when dust evaporates. We argue that the rim shape is
controlled by a fundamental property of circumstellar disks, namely their very
large vertical density gradient, through the dependence of grain evaporation
temperature on gas density. As a result, the bright side of the rim is
"curved", rather than "vertical", as expected when a constant evaporation
temperature is assumed. We have computed a number of rim models, which take
into account this effect in a self-consistent way. The results show that the
curved rim (as the vertical rim) emits most of its radiation in the near and
mid-IR, and provides a simple explanation to the observed values of the near-IR
excess (the "3 micron bump" of Herbig Ae stars). Contrary to the vertical rim,
for curved rims the near-IR excess does not depend much on the inclination,
being maximum for face-on objects. We have then computed synthetic images of
the curved rim seen under different inclinations; face-on rims are seen as
bright, centrally symmetric rings on the sky; increasing the inclination, the
rim takes an elliptical shape, with one side brighter than the other.
