Rotating the card shell-define the pair point)

Tangent to Vertex

Returns a convex polygon.P, TangentLIsPIntersection andPInternalL.

This concept is similar to orthogonal tangent.

Pair of vertex points

If two verticesPAndQ(BelongP) In the two parallel tangent lines, they form a pair of attention points.

Two different parallel tangent always determine at least one pair of vertex pairs. There are three situations based on the intersection of the line and the polygon:

1. "Point-to-point"
2. "Point-edge" pair of vertex points
3. Edge-edge pair

Case 1 occurs when the tangent pair and the polygon have only two intersections. The black spots on the way constitute a pair of hidden points.

Case 2 occurs when the intersection of a tangent and a polygon is an edge and the tangent of the other is unique to the tangent of the polygon. Note that the existence of this tangent must include the existence of two different vertex-vertex pairs.

Case 3 occurs when the tangent and polygon are parallel edges. In this case, the tangent also determines four different vertex-vertex pairs.

 

Original article address:Http://cgm.cs.mcgill.ca /~ Orm/app.html

 

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