Metrics and generation specifications for comparing volume-rendered images

The goal of this paper is to lay a foundation for objectively comparing volume-rendered images, leading to objective evaluation of their accuracy and quality. The key elements of the foundation are: (1) a rigorous specification of all the input and parameters that need to be specified to define the conditions under which a volume-rendered image is generated; and (2) the basis for a methodology for difference classification, including a suite of functions or metrics to quantify and classify the difference between two volume-rendered images that will support an analysis of the relative importance of particular differences. The results of this method can be used to study the changes caused by modifying particular parameter values, to compare and quantify changes between images of similar data sets rendered in the same way, and to detect errors in the design, implementation or modification of a volume-rendering system. If a benchmark image is available, for example one created by a high-accuracy volume-rendering system, the method can be used to evaluate the accuracy of a given image. The key contribution of this paper is the separation of the difference into noise, bias and structured difference components. Copyright © 1999 John Wiley & Sons, Ltd.