Pre-rendering
Contrary to real-time rendering, performance is only of second priority with pre-rendering. It is used mainly in the film industry to create high-quality renderings of lifelike scenes. Many special effects in today's movies are entirely or partially created by computer graphics. For example, the character of Gollum in the Peter Jackson The Lord of the Rings films is completely computer-generated imagery (CGI). Also for animation movies, CGI is gaining popularity. Most notably Pixar has produced a series of movies such as Toy Story and Finding Nemo, and the Blender Foundation the world's first open movie Elephants Dream.
Because of the need for very high-quality and diversity of effects, offline rendering requires a lot of flexibility. Even though commercial real-time graphics hardware is getting higher quality and more programmable by the day, most photorealistic CGI still requires software rendering. Pixar's RenderMan, for example, allows shaders of unlimited length and complexity, demanding a general-purpose processor. Techniques for high realism like raytracing and global illumination are also inherently unsuited for hardware implementation and in most cases are realized purely in software.
Read more about this topic: Software Rendering