Many rendering packages provide easy access to 30 standard IES Patterns which you can apply to lights.
Here are samples of 6 of them.
You can easily select one of these patterns and render your model using it.
IES light files are created by many major lighting manufacturers and can be downloaded freely from their sites.
IRender nXt also provides 30 standard IES Light profiles which can be used to create many standard lighting shapes.
Read More: Select IES Patterns