Patent ID: 6014143
Filing Date: 2000-01-11
Classification: G06T

Abstract:
A ray transform method for a fast perspective view volume rendering of a volume data set for rendering said volume data set on a 2D graphics display of a computer system, said method comprising the steps of:(a) expressing at least one destination voxel of a ray as a homogeneous coordinate having an x value, a y value, a z value, and a w value;(b) determining a distance value for a projection plane for a desired perspective view;(c) generating a ray transform matrix associated with a pixel location, said pixel location having an X component and a Y component, and said x value and said y value of said at least one destination voxel of said ray expressed as said homogeneous coordinate, said ray transform matrix further comprising a z-vector wherein said z-vector has an iR component and a jR component;(d) initializing all values for said ray transform matrix except for said iR component and said jR component;(e) initializing said iR component and said jR component of said z-vector of said ray transform matrix by dividing said X component of said pixel location by said distance value for said iR component and dividing said Y component of said pixel value by said distance value for said jR component;(f) generating an inverse orthographic model-view matrix, said inverse orthographic model-view matrix having homogeneous coordinates;(g) multiplying said inverse orthographic model-view matrix by said ray transform matrix yielding a combined inverse matrix;(h) multiplying said at least one destination voxel expressed as said homogeneous coordinate by said combined inverse matrix, yielding an inverse transformed sample point, said inverse transformed sample point having an x' coordinate value, a y' coordinate value, and a z' coordinate value;(i) adding 0.5 to each of said x' coordinate value, said y' coordinate value, and said z' coordinate value of said inverse transformed sample point;(j) determining a beginning neighborhood point;(k) determining a neighborhood of eight source voxels surrounding said beginning neighborhood point;(l) determining a nearest neighborhood source voxel from said neighborhood of eight source voxels in relation to said beginning neighborhood point, said nearest neighborhood source voxel having a source value; and(m) assigning said source value of said nearest neighbor source voxel to said inverse transformed sample point, wherein said source value is used in the further rendering process for said inverse transformed sample point.