1. A method for visualizing changes in a three dimensional (3D) model, comprising: generating initial environmental information by placing light sources at known coordinates when an initial 2D photograph of a person's hair is taken; receiving the initial 2D photograph of the person's hair; receiving an initial 3D model of the person's hair; designing a virtual hair growth, for the person's hair based at least partially on the initial 2D photograph, the initial 3D model, and a growth model using a database of prior hair growth information; determining a target 3D model of the hair for the person based on the initial 3D model and the virtual hair growth; mapping the hair from the initial 3D model to the target 3D model; interpolating between the initial 3D model and the target 3D model to determine a post-hair growth 3D model of the hair, including: generating a complete 3D model of the hair of the person using the person's 3D geometry, texture, shadow, and shading, that includes bone, teeth, gingiva, joint, muscle, soft tissue, and skin information; and adding missing data from one or more of the bone, teeth, gingiva, joint, muscle, soft tissue, and skin information from a database of known hair models; inputting the coordinates to the post-hair growth 3D model; rendering a 2D photo realistic image of the hair of the person based on the post hair growth 3D model; and displaying the 2D photo realistic image; wherein the method is performed by a computer.