A rendering system having a customizable database of compositing rule tables that define how the input volumes are to be combined based on the their type, i.e. anatomical, functional, etc. The system also allows for the customization of the transfer function types associated with each type of input volume. Enabling this customization is a modularization of the rendering system such that the image formation process is shielded form the actual input volume configuration. This includes the building of a database of shaders that embody the compositing rules defined in a selected table matching the input volume configuration. This shader database in conjunction with a spatially subdivided/bricked representation of the input volumes allows the system to manage the overall complexity of the image formation process by locally selecting the cheapest/least complex shader. Thus allowing for more complex compositing rules with minimal impact on the rendering performance.