Patent ID: 6567087
Filing Date: 2003-05-20
Classification: G06F,G06T

Abstract:
A method to create a large-area, relatively-high-resolution simulated terrain having realistic topography for use with a real-time dynamic vehicle model virtually traversing the simulated terrain and reacting thereto in conjunction with human driver inputs, the method of creating the simulated terrain database comprising:choosing a fractal dimension for the simulated terrain; choosing a desired magnitude for the simulated terrain in terms of a root-mean-square value; choosing a maximum and a minimum frequency to be used in generating the simulated terrain; accessing a relatively lower-resolution simulated terrain database wherein a three-dimensional terrain is represented by a multiplicity of joined polygons having the same size and shape; generating an array of points in a spectral domain by using the fractal dimension, the desired magnitude and the maximum and minimum frequencies, the array in the spectral domain representing a spectral fractal Brownian surface; wherein each point of the spectral array is defined in term of amplitude and phase, the amplitude is a random gaussian number and the phase is a random number between 0 and 2&pgr;; wherein the amplitude is multiplied by a scaling factor of {square root over (1/(u2+v2)H+1)}, where the array of points in the spectral domain has a u-axis and a v-axis, the particular values for u and v at any given point are used for the scaling factor of that point, and H is a Hurst exponent; performing low-pass filtering on the array in the spectral domain to eliminate frequencies above the maximum frequency; performing high-pass filtering on the array in the spectral domain to eliminate frequencies below the minimum frequency; after the high pass filtering and the low-pass filtering, transforming the array in the spectral domain into an array of points in a spatial domain, the array in the spatial domain representing a surface patch lying over an area having a same size and shape as one of the polygons of the lower-resolution terrain database performing a further filtering on the array in the spatial domain such that sides of the surface patch have a same spatial position and orientation as corresponding sides of the one polygon; after the further filtering, designating points of the array in the spatial domain as NURBS control points; for remaining polygons in the relatively lower-resolution simulated terrain database, repeating the steps of generating an array of points in the spectral domain, performing low-pass filtering, performing high-pass filtering, transforming, performing the further filtering, and designating the points of the array in the spatial domain as NURBS control points; adjusting the NURBS control points in non-edge rows and columns of the spatial arrays that are adjacent to rows and columns on edges of the spatial arrays to achieve G1 geometric continuity among the spatial arrays; storing the spatial arrays in a memory; using a computer to generate a relatively-high-resolution terrain from the spatial arrays in a zone of the simulated terrain where a vehicle represented by the dynamic model is located.