Experimental Validation of Radiance-Based Methods for Simulating Solar Penumbras and Pinhole Projections

The sun’s vast size creates two distinct shadow phenomena on Earth: solar penumbras and pinhole projections. These sunlight effects are particularly important in daylight perception research and exacting daylighting design. As such, a method to generate accurate and efficient lighting simulations of these sunlight effects is needed to facilitate research and design applications. The present study is the first to investigate the accuracy of three Radiance-based methods for generating solar penumbras and pinhole projections against real-world measurements using various semi-controlled scenarios. In addition, we examine the applicability of these methods in terms of simulation time and file size. These methods involve the use of Radiance’s direct jittering algorithm, utilizing solely Radiance’s stochastic calculation, and subdividing a Radiance sun into many small suns. The simulation results of solar penumbras and pinhole projections per method are compared to real-world measurement data and assessed on their applicability. The results show that employing a subdivided sun offers an accurate and efficient method for simulating scenes with solar penumbras and pinhole projections using Radiance.