  We present synthetic observations of star-forming interstellar medium
structures obtained by hydrodynamic calculations of a turbulent box under the
influence of an ionising radiation field. The morphological appearance of the
pillar-like structures in optical emission lines is found to be very similar to
observations of nearby star forming regions. We calculate line profiles as a
function of position along the pillars for collisionally excited [OIII]5007,
[NII]6584 and [SII]6717, which show typical FWHM of 2--4 km/s. Spatially
resolved emission line diagnostic diagrams are also presented which show values
in general agreement with observations of similar regions. The diagrams,
however, also highlight significant spatial variations in the line ratios,
including values that would be classically interpreted as shocked regions based
on one-dimensional photoionisation calculations. These values tend to be
instead the result of lines of sight intersecting which intersect for large
portions of their lenghts the ionised-to-neutral transition regions in the gas.
We caution therefore against a straightforward application of classical
diagnostic diagrams and one--dimensional photoionisation calculations to
spatially resolved observations of complex three-dimensional star forming
regions.
