Layers for effective volume rendering

Abstract

A multi-layer volume rendering framework is presented. The final image is obtained by compositing a number of renderings, each being represented as a separate layer. This layer-centric framework provides a rich set of 2D operators and interactions, allowing both greater freedom and a more intuitive 2D-based user interaction. We extend the concept of compositing which is traditionally thought of as pertaining to the Porter and Duff compositing operators to a more general and flexible set of functions. In addition to developing new functional compositing operators, the user can control each individual layer's attributes, such as the opacity. They can also easily add or remove a layer from the composition set, change their order in the composition, and export and import the layers in a format readily utilized in a 2D paint package. This broad space of composition functions allows for a wide variety of effects and we present several in the context of volume rendering, including two-level volume rendering, masking, and magnification. We also discuss the integration of a 3D volume rendering engine with our 2.5D layer compositing engine.