fl_beam

The shaft of sunlight the Facer throws off the bronze plate.

The geometry it draws is a hollow cone shell, so what has to be painted is the thickness of air a viewing ray crosses. That thickness is greatest where the surface faces the camera and least at the silhouette, which is what the angle between the surface and the view measures — so the shell is brightest down its visual centre and falls to nothing at its edges, and the shaft reads as a volume rather than as a cone of card.

Along its length it opens out of the plate over the first tenth, carries a slow travelling grain at two rates so it never reads as one scrolling band, and dies into the ground at the far end. The core runs hotter than the mantle: near-white where it leaves the plate, settling to amber down the shaft.

Written for additive compositing with no depth write, so the shaft adds light to the hill and never darkens what stands behind it.