| 摘要 |
PURPOSE:To remarkably improve approximation accuracy by approximating the respective small sections of a curved surface displayed by a B-spline curved surface information by a protruding polyhedron formed by control points of Bejier curved surface. CONSTITUTION:The B-spline curved surface information maintaining section 2 delivers the B-spline curved surface information (BS information) relating to small sections of the curved surfaces (a), (b) corresponding to patch numbers designated from a control section 1 to a Bejier converting section 3. The converting section 3 respectively Bejier converts the BS informations of the small sections of the curved surfaces (a), (b) received from the BS information maintaining section 2 to calculate two sets of protruding polyhedrons having vertexes of control points of the respective Bejier curved surfaces and delivers to a two vertex selecting section 4 and a three vertex selecting section 5. A cross judging section 6 judges the existence of the cross of a segment including the two vertexes received from the selecting section 4 and a triangle including the three vertexes received from the selecting section 5 and informs this judging result to the control section 1. Thus, the approximation accuracy is remarkably enhanced and the cross of the segment and the triangle shape is judged, so that the time required for the judgement is shortened and the high speed can be realized.
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