Path tracing is a method for generating digital images by simulating how light would interact with objects in a virtual world. The path of light is traced by shooting rays (line segments) into the scene and tracking them as they bounce between objects. Path tracing gets its name from calculating the full path of light from a light source to the camera. Light can potentially bounce between many objects inside the virtual scene. As a ray of light hits a surface, it bounces and creates new rays of light. A path can therefore consists of a number of rays. By collecting all of the rays along a path together, the contributions of a light source and the surfaces along the path can be calculated. These calculations are used to produce a final image. In many versions of path tracing (including the approach Hyperion takes), paths are started from the camera and shot into the scene to find connections to light sources. This is the opposite of how light behaves in the real world, but by doing this backwards, it is much easier to find light paths that will actually hit the camera.