三点，与锚点

Synopsis

obj = GCONIC/point1,point2,point3,ANCHOR,point4

Description

Creates a general conic by specifying three previously defined points containing the conic and a fourth point which serves as an anchor. The first and the third points are the beginning and end of the conic, respectively.

Parameters

Parameter

Description

point1,point2,point3

Three previously defined points which are on the curve. All of the points must be coplanar, however, points 1,2 and 3 may not be collinear. The points must be specified individually if an array is used.

ANCHOR

Minor word that indicates that a known anchor point is to be specified.

point4

A previously defined point which is called the anchor point. Imaginary lines from this point to the first and third points forms angles which represent the tangents of the conic at the beginning and end respectively.

Example

This example demonstrates the creation of a general conic through three points and controlled by a fourth, anchor point.

Declaration

ENTITY/P(4),GC1

Geometry Definition

P(1)=POINT/-1.5,-.5
P(2)=POINT/0,0
P(3)=POINT/1,-.5
P(4)=POINT/0,-1

Conic Definition

GC1 = GCONIC/P(1),P(2),P(3),ANCHOR,P(4)

General Conic Created Using Three Points and an Anchor

Parameter	Description
point1,point2,point3	Three previously defined points which are on the curve. All of the points must be coplanar, however, points 1,2 and 3 may not be collinear. The points must be specified individually if an array is used.
ANCHOR	Minor word that indicates that a known anchor point is to be specified.
point4	A previously defined point which is called the anchor point. Imaginary lines from this point to the first and third points forms angles which represent the tangents of the conic at the beginning and end respectively.