< II> ObjectARX development: create and edit basic graphic objects

   I'm learning ObjectARX When , Once tried to learn the operation of database directly 、 Concepts such as geometric classes , result
Not ideal . After a period of groping , I will create and edit basic graphic objects as a breakthrough , Step by step , stay
A strong sense of achievement in the learning process .

One 、 Include content

Basic primitive creation functions include ：
// Create a line
// Create circles // Two point method to create a circle // Three point method to create a circle
// Create an arc // Three point method to create an arc // The starting point 、 center of a circle 、 Create an arc at the end point // The starting point 、 center of a circle 、 Arc angle creates an arc
// Create optimized polylines // Create a 3D polyline // Create regular polygons // Create a rectangle // Create a circular polyline // Create a polyline of an arc
// Create regions
// Create a spline
// Create ellipse // Create an ellipse from the circumscribed rectangle
// Create a fill
// Create a single line of text // Create multiline text
// Align labels // Corner dimensions // Radius marking // Diameter marking // Angle labeling // Coordinate notation

Two 、 Content explanation

Now let's explain how to create a straight line AutoCAD The basic structure of the database .
Create a line , You need to specify the start point and end point .
Before proceeding , We must introduce some basic terms of database ：
 surface ： Tables are the constituent units of databases , A database contains at least one table .
 Record ： Records are the constituent units of tables , A table may contain multiple records , It may not contain any records .
The following figure is used to describe AutoCAD The basic structure of the database is the best . From the picture , Entities are contained in block notation
Recording , So create a graphic object , The following basic steps need to be followed ：
（1） Determine the drawing database of the object to be created ;
（2ÿ