How is distant directional light source(like sun) added in BDPT? If this is an indoor scene that gets sunlight through windows, how is this handled in BDPT(other than to consider Sun as a big disc far away and to sample a position on it's area, as this probably wouldn't be efficient for points within the room)
Would it be valid instead to consider window polylines as area sources that emits light in one direction(directional source)? The light samplePosition would be same as sampling a point on the window area (with pdf 1/A ?) and sampleDirection with pdf=1? How about connecting s=1 and t and MIS weights? are they need to be modified or same codes can be used?
Any help/hint is appreciated, Thanks.