[AN94]
Cornell University Program of Computer Graphics 

IsoContour volume rendering.James Arvo and Kevin Novins.In Arie Kaufman and Wolfgang Krueger, editors, 1994 Symposium on Volume Visualization, pages 115122. ACM SIGGRAPH, October 1994. In this paper we present a new approach to volume rendering in which curves of constant intensity in image space, or isocontours, are computed directly for each view. The generated isocontours can be used to drive various visualization and featuredetection algorithms. The approach imposes no restriction on the organization of the data points and can accommodate a large class of radiallysymmetric filter functions. The technique works well for both perspective and orthographic viewing projections. Each isocontour is defined by an ordinary differential equation, which is solved numerically using a predictorcorrector method. A key element of the algorithm is the use of image intensity gradients, which we compute by means of a closedform expression that holds at every point in the image plane. A caching algorithm is described that dramatically accelerates the gradient computations on large datasets. The algorithm is demonstrated on emissiononly datasets. We conclude by describing a number of possible enhancements. This paper is available as a compressed Postscript file AN94.ps.gz (157K).
 
