A customer recently informed us that their attempt to use DirectRT on an Intel Mac within Parallels (an emulation program) failed. Parallels is great because you can have an active OS X desktop and run Windows in a second... 'window.' If your accounting program or CAD program is only available under Windows, this is a great solution.
However, DirectRT may fail in the Parallels environment. This is primarily because DirectRT requires the OS to give it direct access to the system hardware and Parallels does not offer this in the way that BootCamp does.
Bottom line is that, so far, BootCamp seems the way to go. As stated above, just use BootCamp to reboot into an actual Windows environment on your Mac and you ought to be fine running DirectRT.