Re: backward ray tracing

surface2air wrote:
can any on explain what this phenomenon actually is and why its better
than forward ray tracing.

It's just what it sounds like. Ray propagation is an abstraction of Maxwell's equations in the short-wavelength limit, and Maxwell's equations are symmetrical with respect to time reversal.

As to when and if it's better, you need to re-read your textbook.

Cheers,

Phil Hobbs
.