Working in 3D in AutoCAD is the result of coordination between Axis System, Coordinate System, and Viewpoint. Users need to understand these three basics in order to operate correctly. Axes and Perspective Shift have been mentioned in previous chapters.

Now here comes the matter of the Coordinate System (Coordinate System). The word Coordinate means to tell the position, or any point caused by the intersection of the axes in AutoCAD, represented by x,y (2 dimensions) and x,y values. ,z (3 dimensions) or called Cartesian coordinates the program will start drawing a line or shape from starting coordinates Continue to the next coordinate until it is finished.

Specifying the length or line distance Continue from the beginning, called the offset world (@), for example, starting at point 0,0 (x=0, y=0), continue to draw a horizontal line 10 units long, which is 10,0 (x=10, y =0) because the horizontal axis is the X axis, then enter at the end of the command will get a horizontal line of length 10 units.

In addition to AutoCAD, it uses the Polar coordinate system. It helps to create jobs as well. This coordinate system, in simple terms, uses angles as an assistant to determine direction. The degree angle will increase in the counterclockwise direction as shown in the FIGURE 1.

For example, specifying coordinates like this. For example, starting at point 0,0 (x=0, y=0), continue to draw a line horizontally 10 units long, which is 10<0 (x=10,0 degrees) because the horizontal axis is at 0 degrees, then enter. End. The command will get a horizontal line of length 10 units.

If we want to create a 10 x 20-unit square with straight lines, how do we do it?

Starting at point 0,0 (x=0,y=0), continue to draw a line horizontally, length 10 units, that is, @10<0 (x=10,0 degrees). vertically, length 20 units, @20<270 (y=20,270 degrees), a vertical line of length 20 units.

Then draw a line horizontally, length 10 units, @10<180 (x=10,180 degrees), a horizontal line of length 10 units to the left. And continue to draw a line vertically, length 20 units, that is, @20<90 (y=20,90 degrees) get a vertical line, length 20 units, will get a closed rectangle, size 10 x 20 units.