Strictly spoken it's a piece of software, simulating the Solar System's bodies in 3D on your Windows or Linux PC (will work in most *NIX's as well). In difference to quite a few other programs it does so in realtime. Meaning you can view all the planets, moons and spaceships move along their paths, trace them, follow them, orbit them and even control them (time and spaceship contol). And you won't have to fight your way through hordes of green, slimey and one-eyed aliens for that ;-)
New in blender is a physically based volume material type, intended for rendering participating media, such as smoke, clouds, fog, and other volumetric effects. All procedural textures are supported as data sources, as well as two new textures for rendering voxels (such as our the smoke simulator) and point clouds.
Spectral rendering The core of Luxrender is fully spectral. Unlike traditional rendering software, which only operates on distinct colors (such as red, green and blue), Luxrender uses individual wavelengths. This allows LuxRender to correctly deal with wavelength dependent effects, such as dispersion, or accurately capture the color of incandescent lights. It also makes the rendered images look more natural.
These images are hemispherical panoramas, taken as addition to my Virtualvienna Project. You can find there some of the panoramas as full panorama in a bigger size than here.