Bifacial Solar Panel 2D: Ground-View Ray Model

This is a genuinely two-dimensional companion to the 3D bifacial-panel simulator: instead of a rendered scene, it works the cross-section directly with ray geometry. The front and rear faces of the tilted panel each get an exact, textbook view factor to an infinite ground plane, and the rear face's view is then checked ray-by-ray against a modeled neighboring-row rail to see how much of it is actually blocked at the current mounting height — a real visibility computation standing in for the 3D version's fitted height-correction curve. Adjust ground material, mounting height, tilt and sun elevation to watch the front/rear/total power curves respond, and see exactly how much of the rear hemisphere clears the rail at any given height.