1. A method for converting animation of an object from a first tool to a representation used in a runtime animation system, wherein the first tool represents the object using a source skin, wherein the runtime animation engine uses a target structure, a target skin and shading, the method comprising: using the animation of the object from the first tool, generating information describing a set of virtual bones added to the target structure, skinning weights for associating the target skin with the virtual bones and animated deformation data specifying movement of the virtual bones for each frame of animation; and using the animation of the object from the first tool, generating information describing a set of normal maps, one or more masks and animated mask parameters for use by one or more shaders for the runtime animation system.