Transform TracingHeight distributional distance transform (HDDT) methods are introduced as a new class of methods for height field ray tracing. HDDT methods utilize results of height field preprocessing. The preprocessing involves computing a height field transform representing an array of cone-like volumes of empty space above the height field surface that are as wide as possible. There is one cone-like volume balanced on its apex centered above each height field cell. Various height field transforms of this type are developed. Each is based on distance transforms of height field horizontal cross-sections. HDDT methods trace rays through empty cone-like volumes instead of through successive height field cells. The performance of HDDT methods is evaluated experimentally against existing height field ray tracing methods.
A new morphological algorithm for automated interpolation of height grids from contour images is developed. Explicit identification of contours within the image is not necessary since interpolation is done directly in image space using morphologic iransforms and labeling schemes. 3-D depth-shaded perspective images of height grids for specified viewing angles are generated using transformed height columns. These methods avoid the processing associated with intermediate contour and polygonal representations. Co-registered continuous tone (gray scale) image data is mapped onto the 3-D views.Advantages of this new recursive algorithm include the ability to interpolate and label whole families of points simultaneously and the basing of interpolated values on surrounding contour morphology. In addition, the methodology for decomposition and labeling of contour intervals is directly amenable to parallel implementation.
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