The dust in the inner region of PPDs is the base material for terrestrial planet formation. The arrival of PIONIER, GRAVITY and MATISSE allows spatially resolved high quality observations of this region. Interferometric observations are often interpreted using simplified components to describe the source emission. To find out how results derived in this way relate to the true structure and physics of this region, we created physical models including dust evaporation and formation and "observed" these models in the same way as observations are treated. The inner rim position can be very well constrained, even for only partially resolved objects, and the radial extend of the rim to within a factor of 2, but not better, for resolved objects. Comparing with the recent PIONIER survey of Lazareff17, we find that the rim position of most Herbig stars can be explained using olivine grains with an MRN like size distribution, but also with small olivine grains and the presence of forsterite or iron. For some objects, we can not re-create the amount of NIR flux from the rim, indicating that additional components like disk winds or MHD effects should be included in the modelling process.