Automating Transfer Function Design Based on Topology Analysis

Direct Volume Rendering (DVR) is commonly used to visualize scalar fields. Quality and significance of rendered images depend on the choice of appropriate transfer functions that assigns optical properties (e.g., color and opacity) to scalar values. We present a method that automatically generates a transfer function based on the topological behavior of a scalar field. Given a scalar field defined by piecewise trilinear interpolation over a rectilinear grid, we find a set of critical isovalues for which the topology of an isosurface, i.e., a surface representing all locations where the scalar field assumes a certain value v, changes. We then generate a transfer function that emphasizes on scalar values around those critical isovalues. Images rendered using the resulting transfer function reveal the fundamental topological structure of a scalar data set.