Fractional visibility estimation using particle density for light transport simulation

Abstract

In various examples, transmittance may be computed using a power-series expansion of an exponential integral of a density function. A term of the power-series expansion may be evaluated as a combination of values of the term for different orderings of samples in the power-series expansion. A sample may be computed from a combination of values at spaced intervals along the function and a discontinuity may be compensated for based at least on determining a version of the function that includes an alignment of a first point with a second point of the function. Rather than arbitrarily or manually selecting a pivot used to expand the power-series, the pivot may be computed as an average of values of the function. The transmittance estimation may be computed from the power-series expansion using a value used to compute the pivot (for a biased estimate) or using all different values (for an unbiased estimate).