Basic Creation Method

An ARC can be defined in three ways:

• by defining the positions of the end-points and a ‘through’ point (from which the values of Radius (RADI) and Angle Subtended (ASUB) can be derived if required).

• by defining the position of the centre point, ‘from’ point and Angle Subtended (from which the position of the ‘to’ points and the value of RADI can be derived if required).

• by defining the position of the centre point and two end points.

The method:

NEW ARC

DEF @

results in three points being prompted for (the ‘start’, ‘end’ and ‘through’ points). A line is drawn through the points and TCOD is set to ENDPOINT. A second method is available. Refer to Position (absolute) (of an arc point)) for further information. If used with an existing ARC any existing values of RADI and ASUB are altered accordingly.

Defining or redefining an Arc with a centre- and two endpoints is achieved using the command:

ADEFine <dfnpt> <dfnpt> <dfnpt>

where <dfnpt> defines a position (2D, 3D, p-point).

The first two points are the centre - (CPT) and ‘from’ point (FPT) of the Arc. These two points define the radius. The third point defines the angle subtended by the arc. The TO-point (TPT) lies in this direction from the Centre (CPT) at the same distance as the FPT from the CPT. The TCOD attribute is set to CENTRE.

The command can also be used with the cursor:

ADEFine @

A prompt requests three 2D points to be input for CPT, FPT and angle subtended. 3D points can also be input using the cursor:

ADEFine ID@ ID@ ID@

DEFine IDP@ IDP@ IDP@