| 摘要 |
PURPOSE:To calculate the starting point and the end point of a straight line at a high speed when a circular arc appears to be the straight line by making a circular arc itself into a center and considering the position relation of the starting point and the end point in a plane including the circular arc. CONSTITUTION:By the relation of the position of a starting point C1 and ane an end point C2 of a circular arc and a radius (r) of the circular arc in a plane perpendicular to a normal vector NV of the three-dimensional circular arc, namely, the plane specified by a (z) axis and a (u) axis, a starting angle sang [angle formed by a (x)-(y) plane and the vector from a central point to the starting point C1 of the circular arc] and an end angle eang [angle formed by a (x)-(y) plane and the vector from the central point to a starting point C2 of a circular arc] of the circular arc in the plane are calculated at a first processing process P1. At a second processing process P2, it is determined by the relation of the starting angle sang and the end angle eang of the circular arc which of the starting point C1 and end point C2 of the three-dimensional circular arc or two edge points T1 and T2 composed of the intersection of the circle and the projection surface including the circular arc a starting point A and an end point B of the line segment to be obtained while the circular arc is projected are. Thus, when the circular arc appears to be the straight line, the starting line and the end line of the straight line can be calculated at a high speed. |
