DonPMitchell

Testing the illumination physics in a new C++ ray tracing project. Light is represented by 8 spectral samples, and full complex refractive index and Fresnel law simulated. Materials have surface micro-structure/bumpmap and solid material properties that are separate. Four spheres of gold, green glass, plastic, and air pass through 2-meter cubes of water and glass. Note that the surface bumps, Fresnel and internal reflection effects of the green glass disappear when it enters the glass cube with the same refractive index. The shiny plastic sphere becomes dull in the water, because the resin has same refractive index and only the pigmented material interacts.

Modern "smokeless" gunpowder is a blend of nitrocellulose and other nitrate explosives. Before that, guns, cannons and rockets used black powder, which was invented in China centuries ago. This is a mix of charcoal, sulfur and potassium nitrate, and it must be ground to extreme fineness with a ball mill.