1. A computer-implemented system for fused volumetric rendering of a scene from a set of volumetric scans acquired from different imaging modalities, the system implemented by the computer comprising: a central processing unit; a compositing rule table database having therein a plurality of compositing rule tables, wherein each table provides compositing rules for a different combination of volumetric scans into the rendered scene; a data manager for receiving the volumetric scans and for building therefrom a render queue having a list of volume bricks that represents the volumetric scans in graphics memory, for determining a type signature based on the types and sequence of the volumetric scans representing the scene, and for preparing specific volumetric scans for rendering by packing the specific volumetric scans into 3D textures, wherein each brick in the render queue provides texture coordinates to retrieve the data from the 3D textures; a shader builder for receiving shader functionality and the type signature of the volumetric scans from the data manager, for receiving transfer functions for each volumetric scan, and for selecting a compositing rule table from the database based on the type signature of the volumetric scans and for building a plurality of shaders from a library of graphics functions based on the received shader functionality and selected compositing rule table; and a sampler that receives the render queue, the 3D textures, and the plurality of shaders for rendering a final image of the volumetric scans, wherein for each brick contained in the render queue the sampler determines the least complex shader based on the render parameters and transfer functions in the scene, and binds such shader and the required 3D textures to form the final image one brick at a time.