Have you tried any of the examples at the solution center?
From my understanding only solid geometry in supported, but then I am not an expert.
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If you use NX11, and your body is a "convergent" one, then I'd guess that UF_MODL_trace_a_ray will work. Convergent bodies are real solid bodies, even though their faces are facetted "mesh" surfaces.
But, this is just a guess -- I haven't tried it myself.