1. A method for visualizing diffusion-tensor magnetic resonance images comprising the steps of: providing a diffusion-tensor magnetic resonance image (DT-MRI) volume, said image volume comprising a plurality of 3×3 diffusion tensors associated with a 3-dimensional grid of voxels; positioning and orienting a virtual camera for rendering said volume, said camera having an image plane, said camera's orientation being defined by its look, right and up vectors; associating a billboard with each voxel, each said billboard being parallel with the image plane of the camera, wherein said look, right and up vectors are used to orient each said billboard; applying a texture to each billboard, each said texture being transformed by the inverse of the diffusion tensor associated with the voxel to which the billboard is associated; and rendering said volume by rendering each visible billboard in said image volume, wherein a 2-dimensional (2D) visualization of said DT-MRI is produced.