Infinigen is a procedural generator that creates everything entirely from randomized mathematical rules, including all shapes and materials, from macro structures to micro details. Infinigen can create unlimited variations. Users have full control the generation of assets by overriding default parameters of randomization. Infinigen provides generators for diverse objects and scenes in the natural world including plants, animals, terrains, and natural phenomena such as fire, cloud, rain, and snow. The current focus on nature is motivated by the observation that mammalian vision evolved in the natural world. However, Infinigen is expected to expand over time to cover built environments and artificial objects.