| 摘要 |
An image (MI) is defined, in correspondence with a predetermined polyhedral meshing of a portion of space, by a digital value for each vertex of the meshing. A polygon processing (30; 1450; 1650) receives a representation of a plane polygon (F) with p vertices, p respective values for these p vertices, and a threshold (S); it supplies, in correspondence with the polygon F, a list of oriented segments linking points of the edges of the polygon which are interpolated as equal to the threshold, with a predetermined direction convention. A polyhedron processing (20; 1445; 1645) receives a representation of a polyhedron (POLYED) with the values at its vertices and a threshold; then it invokes the polygon processing means (30) for all the faces of the polyhedron, which supplies a list of oriented segments; then it associates with a polyhedron a list of closed and oriented cycles, constituted by segments of the said list of segments. Main processing means (10; 1440; 1640) sequentially present a plurality of polyhedrons of the said meshing to the polyhedron processing means, with the values associated with their vertices and a threshold. The cycles thus obtained belong to an iso-surface of the image for the said threshold value. <IMAGE> |
