Efficiently simulating realistic lens systems has been a thing for a while; the original paper by Kolb, Mitchell, and Hanrahan is here: https://www.cs.utexas.ed

Efficiently simulating realistic lens systems has been a thing for a while; the original paper by Kolb, Mitchell, and Hanrahan is here: https://www.cs.utexas.edu/~fussell/courses/cs395t/lens.pdf https://www.cs.utexas.edu/~fussell/courses/cs395t/lens.pdf. In the paper they talk about how to apply importance sampling, which is the key to efficiency in bidirectional path tracing. What does this package offer beyond that?