We use 3-D radiative transfer models to show the effects of clumpy circumstellar material on the observed infrared colors of high mass stars embedded in molecular clouds .
We highlight differences between 3-D clumpy and 1-D smooth models which can affect the interpretation of data .
We discuss several important properties of the emergent spectral energy distribution ( SED ) : More near-infrared light ( scattered and direct from the central source ) can escape than in smooth 1-D models .
The near- and mid-infrared SED of the same object can vary significantly with viewing angle , depending on the clump geometry along the sightline .
Even the wavelength-integrated flux can vary with angle by more than a factor of two .
Objects with the same average circumstellar dust distribution can have very different near- and mid-IR SEDs depending on the clump geometry and the proximity of the most massive clump to the central source .

Although clumpiness can cause similar objects to have very different SEDs , there are some observable trends .
Near- and mid-infrared colors are sensitive to the weighted average distance of clumps from the central source and to the magnitude of clumpy density variations ( smooth-to-clumpy ratio ) .
Far-infrared emission remains a robust measure of the total dust mass .
We present simulated SEDs , colors , and images for 2MASS and Spitzer filters .
We compare to observations of some UCH ii regions and find that 3-D clumpy models fit better than smooth models .
In particular , clumpy models with fractal dimensions in the range 2.3-2.8 , smooth to clumpy ratios of \lesssim 50 % , and density distributions with shallow average radial density profiles fit the SEDs best ( \left < \rho \right > \propto r ^ { \alpha } , -1.0 < \alpha < 0.0 ) .