| 摘要 |
PURPOSE: To find out a point outside an area independently of the sort of a face on which the area is mounted. CONSTITUTION: The middle point P0 of a prescribed ridge line E0 forming the boundary of a three-dimensional area S is calculated. A cutting plane passing the point P0 is determined and an intersecting line C by the cutting plane is obtained. The normal vector n0 of a face S on the middle point P0 is calculated and the tangent vectors TE1, TE2 of the ridge line on the point PO are calculated. A vector having the same direction as the turning direction of the ridge line E0 out of the vectors TE1, TE2 is set up as TE. The tangent vectors TC1, TC2 of the intersecting line C at the point P0 are calculated, the vector products of the vectors TC1, TC2 and the TE are respectively calculated and the vector TCi (i=1 or 2) having a smaller angle is set up as TC, a perpendicular is drawn from the end point of the vector TC started from the point P0 to the face mounting the area S and an intersecting point between the perpendicular and the area S is extracted as a point outside the area.
|
