Comparison between the inner connections of BDPT and PCBPT.

Implementing Probabilistic Connections for Bidirectional Path Tracing


Light transport simulation algorithms are remarkably adept at recreating a large variety of light phenomena which occur in nature. As such they have seen widespread adoption across the industry, which made it paramount to create efficient and robust algorithms. One recent algorithm which tries to deal with this problem is known as Probabilistic Connections for Bidirectional Path Tracing (PCBPT). It builds upon the classical Bidirectional Path Tracing (BDPT) algorithm. In Bidirectional Path Tracing, a ray is traced from the sensor as well as from the emitter. The two rays are then connected to calculate the light contribution to image pixels. PCBPT extends this idea to support connecting multiple emitter paths to one sensor subpath, and introduces importance sampling as a way of choosing the most suitable emitter paths. Unfortunately, there was no implementation of PCBPT publically available, which is why we implemented it into the open-source Mitsuba renderer. We evaluate the algorithm against standard BDPT on a variety of different scenes. Our comparisons provide insight into what type of scenes PCBPT can help improve and where the additional computational cost presents too much of an overhead.

Bachelor’s thesis at TU Wien

The code will be published soon.