The final modification included in pvTrace v2.1.sv eliminates the geometrical requirements of the incident light mask. In this new approach, rays are generated in an x-by y-shaped rectangle which is just big enough to cover the part, but if a ray misses the part, it is ignored. We can thus generate a cleaner light input consisting only of rays that are incident on the object. We note that any interaction with the geometry is recorded, so transmission losses are still included, meaning the optical efficiency calculated by pvTrace corresponds to external photon efficiency (𝜂 !"# ), as defined in Equation , instead of the internal optical efficiency (𝜂 %&# ), which would only consider absorbed rays in its efficiency calculation (see Equation S2 in Section S3). Figure shows the result of this modification for a leaf LSC, plotting the x-and y-positions and wavelengths of entrance and exit rays.