抛物线

Synopsis

obj = PARABO/point,focal length,dymin,dymax[,ATANGL,angle]

Description

Creates a parabola by specifying a previously defined point which represents the vertex, a focal length, and an X and Y value which limit the length of the curve.

Parameters

Parameter

Description

point

A previously defined point which establishes the vertex.

focal length

The desired distance from the vertex to the focus.

dymin

The minimum "Y" distance, in the coordinate system of the parabola, which controls the sweep of the curve below the axes of symmetry.

dymax

The maximum "Y" distance, in the coordinate system of the parabola, which controls the sweep of the curve above the axes of symmetry.

NOTE: If the value entered for the minimum Y distance is greater than the value entered for the maximum Y distance, the system automatically reverses the two values.

ATANGL

The optional minor word ATANGL indicates that the parabola is to be rotated about the vertex.

angle

The angle at which the parabola rotates about the vertex. The angle is measured in degrees from the positive X axis of the work coordinate system to the axis of symmetry. A positive angle rotates the parabola counterclockwise and a negative angle rotates the parabola clockwise. If not specified the axis of symmetry, as a default, is parallel to the X axis of the work coordinate system.

Example

Creating a parabola by specifying a vertex point, a focal length, limiting X and Y values, and a rotation angle.

Declaration

ENTITY/PT1,PARA1

Geometry Definition

PT1 =POINT/0,0

Parabola Definition

PARA1=PARABO/PT1,.25,-.5,1,ATANGL,30
TERM:HALT

A Parabola Rotated

Parameter	Description
point	A previously defined point which establishes the vertex.
focal length	The desired distance from the vertex to the focus.
dymin	The minimum "Y" distance, in the coordinate system of the parabola, which controls the sweep of the curve below the axes of symmetry.
dymax	The maximum "Y" distance, in the coordinate system of the parabola, which controls the sweep of the curve above the axes of symmetry. NOTE: If the value entered for the minimum Y distance is greater than the value entered for the maximum Y distance, the system automatically reverses the two values.
ATANGL	The optional minor word ATANGL indicates that the parabola is to be rotated about the vertex.
angle	The angle at which the parabola rotates about the vertex. The angle is measured in degrees from the positive X axis of the work coordinate system to the axis of symmetry. A positive angle rotates the parabola counterclockwise and a negative angle rotates the parabola clockwise. If not specified the axis of symmetry, as a default, is parallel to the X axis of the work coordinate system.