2. Drawing Geometric Objects
Lecture Two
Creating 2D Objects 1
Modifying Objects 2
Work with Layers 3 4
Create a Drawing Template File
Drawing Geometric Objects 5
Control Screen Display 6

3. 1.Creating 2D Objects
You can create a range of 2D objects, from simple lines and circles to spline curves, and ellipses. In general, you draw objects by specifying points with the pointing device , by entering coordinate values on the command line or by Draw tool bar.

4. 1.1 Drawing Linear Objects
Draw Lines In a simple line with connected segments, each segment is a separate line object.
Draw Polylines A polyline is a connected sequence of line segments created as a single object. You can create straight line segments, arc segments, or a combination of the two.
Draw Rectangles and Polygons You can create rectangles and regular polygons quickly. Creating polygons is a simple way to draw equilateral triangles, squares, pentagons, hexagons, and so on.
Draw Multiple-Line Objects Multilines are composed of 1 to 16 parallel lines, called elements.

5. Drawing Polylines
A polyline is a connected sequence of line segments created as a single object. You can create straight line segments, arc segments, or a combination of the two.
Multisegmented lines provide editing capabilities unavailable for single lines. For example, you can adjust their width and curvature. After you've created a polyline, you can edit it with PEDIT or use EXPLODE to convert it to individual line and arc segments.

6. 1.1.2 Drawing Rectangles Rectangle modes:
Use RECTANG to create closed polylines in a rectangular shape. You can specify the length, width, area, and rotation parameters. You can also control the type of corners on the rectangle—fillet, chamfer, or square.
Rectangle modes:
Chamfer=5 x Fillet= Chamfer=0 Fillet= Width=5
Rtation= Area=1000 Length=50 Dimensions: Length=100 Width=40

7. Drawing Polygons
Use POLYGON to create closed polylines with between 3 and 1,024
equal-length sides. The following illustrations show polygons created
using three methods. In each case, two points are specified.
Enter number of sides <current>: Enter a value between 3 and 1024 or press ENTER
Specify center of polygon or [Edge]: Specify a point (1) or enter e

8. 1.2 Draw Curved Objects
Curved objects are arcs, circles, polyline arcs, donuts, ellipses, and splines.
Draw Arcs To create an arc, you can specify various combinations of center, endpoint, start point, radius, angle, chord length, and direction values.
Draw Circles To create circles, you can specify various combinations of center, radius, diameter, points on the circumference, and points on other objects.
Draw Donuts Donuts are filled rings or solid-filled circles that actually are closed polylines with width.
Draw Ellipses The shape of an ellipse is determined by two axes that define its length and width. The longer axis is called the major axis, and the shorter one is the minor axis.
1.2.5 Draw Splines A spline is a smooth curve that passes through or near a given set of points. You can control how closely the curve fits the points.

9. 1.2.1 Drawing Arcs (1) Draw Arcs by Specifying Three Points
You can create arcs in several ways.
(1) Draw Arcs by Specifying Three Points
Start, Center, End
(2) Draw Arcs by Specifying Start, Center, Angle
When you have a start point and a center point and the included angle, use the Start, Center, Angle or the Center, Start, Angle option.

10. 1.2.1 Drawing Arcs (3) Draw Arcs by Specifying Start, Center, Length
When you have a start point and a center point you can snap to; when you know the chord length, use the Start, Center, Length or the Center, Start, Length option. The length of the chord of the arc determines the included angle.   
(4) Draw Arcs by Specifying Start, End, Direction/Radius

11. 1.2.1 Drawing Arcs (5) Draw Contiguous Arcs and Lines
Immediately after you complete an arc, you can start a line tangent to the arc at an endpoint by starting the LINE command and pressing ENTER at the Specify First Point prompt. You need to specify only the line length.

12. Drawing Circles
You can create circles in several ways. The default method is to specify
the center and the radius. Three other ways to draw a circle are shown
in the illustration.

13. 1.2.2 Drawing Circles Draw a Circle Tangent to Other Objects
To create a circle that is tangent to other objects, select the objects and then specify the radius of the circle. In the illustrations below, the bold circle is the one being drawn, and points 1 and 2 select the objects to which it is tangent.

14. 1.2.3 Drawing Donuts
Donuts are filled rings or solid-filled circles that actually are closed polylines with width.
To create a donut, you specify its inside and outside diameters and its center. You can continue creating multiple copies with the same diameter by specifying different center points. To create solid-filled circles, specify an inside diameter of 0.
Fill On Fill Off

15. Drawing Ellipses
The shape of an ellipse is determined by two axes that define its length and width.
The longer axis is called the major axis, and the shorter one is the minor axis.
The illustrations below show two different ellipses created by specifying axis and distance. The third point specifies only a distance and does not necessarily designate the axis endpoint.

16. Drawing Splines
A spline is a smooth curve that passes through or near a given set of points. You can control how closely the curve fits the points.
The SPLINE command creates a particular type of spline known as a nonuniform rational B-spline (NURBS) curve. A NURBS curve produces a smooth curve between control points.
You create splines by specifying points. You can close the spline so that the start and endpoints are coincident and tangent.

17. Drawing Points
Point objects are useful as nodes or reference geometry for object snaps and relative offsets.
You can set the style of the points and their size relative to the screen or in absolute units. Changing the style of points

18. 2. Modify Objects
If you want to modify some objects, you must select them in order to be processed . There are many ways to select objects shown in bellow:
When you select some objects, there are many ways to modify the objects shown in bellow:
Erase, Copy, Mirror, Offset, Array, Move, Rotate, Scale, Stretch,
Trim, Extend, Break at Point, Break, Join, Chamfer, Fillet, Explode

19. 3. Work with Layers Layers are like transparent overlays.
Layers are used to group information in a drawing by
function and to enforce linetype, color, and other standards.
Layers are the primary organizational tool used in rawing.

20. Creating and Naming Layers
The Layer Properties Manager is displayed.
If you enter -layer at the Command prompt, LAYER displays prompts on the command line.
[?/Make/Set/New/ON/OFF/Color/Ltype/LWeight/Plot/PStyle/Freeze/Thaw/LOck/Unloc]:

21. 4. Create a Drawing Template File
When you need to create several drawings that use the same conventions
and default settings, you can save time by creating or customizing a
template file instead of specifying the conventions and default settings
each time you start. Conventions and settings commonly stored in
template files include
Unit type and precision
Title blocks, borders
Layer names, Linetypes, Color, Linewide
Snap, Grid, and Ortho settings
Grid limits
Dimension styles
Text styles
By default, drawing template files are stored in the template folder, where
they are easily accessible.

23. 5. Draw Geometric Objects

24. 5. Steps of Drawing Geometric Objects

27. 6.Control Screen Display

28. Exercises After Class Using AutoCAD
Practice One: Making your A3 template file including layers
Practice Two
Practice Three

29. Practice Four Practice Five

30. Consider One Consider Two