Basic drawing tools

Point

Creates a symbol on the drawing that is tied to a specific point. It is defined by

coordinates (x,y,z). It is not necessary to create points when you want to draw

other geometric entities.

Line

Like it says. The user defines two points and AutoCAD constructs a line between

them. Shortcut "l" ....

Construction line tools

Ray = A line with a defined starting point with infinte length at a specified slope.

Xline = An infinite line with no start or end point at a specified slope. Base point

can be snapped with middle point snap mode. Shortcut "xl"

Polyline

Polylines are the main business of most drawings. A polyline is made of

numerous lines/arcs/or both segmented together into one selectable object.

Polylines are quite versatile and the PEDIT(Polyline Edit) command can be used

to access & edit many of the features associated with them. Shortcut "pe"

Polygon

Polygons are regular, multisided shapes such as pentagons, hexagons etc.

When this tool is employed, AutoCAD requests the number of sides desired and

then asks whether the shape is to be defined as sitting on a circle of specified

radius, or by the length of a side. The objects created from this command

become "Closed Polylines" and can be edited using PEDIT.

Rectangle

This is basically a quick way of drawing a four-segment polyline with four right

angles. Shortcut "rec"

Arc

An arc is a circle segment. When using this tool the user can define the arc by

selecting three points through which AutoCAD will generate an arc, or

alternatively the user can define a center point, a radius and a range of degrees

to fill.

Circle

The only variables here are radius and centre point. Shortcut "c"

Spline

Splines are a particular form of curve generated by specific mathematical

equations. The user can select as many vertices as they wish, and AutoCAD will

generate a spline curve that incorporates all these points. Splines are generally

used for cosmetic purposes, as their mathematical complexity makes them hard

to define from a technical design perspective. Shortcut "spl"

Ellipse

Basically an oval. Similar to a circle, except ellipses require a radius to be

defined for both their vertical and horizontal components. Shortcut "el"

Hatch

Hatches are area fills. They can be made up of a solid colour, a gradient (in later

versions of AutoCAD) or more usually a specific pattern. Hatches can be applied

to a particular object such as a looped polyline, or any enclosed area. They can

be (and usually should be) defined as being "associative" which means that if the

area in which they are contained is adjusted, the hatching will update

automatically.

Text

Inserts a text string into the drawing. AutoCAD uses two forms of text entry,

single line and multiline. These are known respectively as DTEXT and MTEXT.

DTEXT is very much a leftover from AutoCAD's early years and there is no real

justification for using it's very basic system when the MTEXT option has features

similar to a conventional text editor.you may also select command TEXT for

undefined area.

Basic Modifying Tools

Erase

Erases the selected object from the drawing. Can also be activated by pressing

the delete key on the keyboard. Shortcut "e" (not very helpful because there is

delete key)

we also erases the objects by selected objects for example. select the objects

which you want to erase and then select the erase tool and press key enter

Copy

Copies the selected object from one point on the drawing to one or more

locations. The user defines two points and the object is copied using these two

positions as base points. For example, the user could select 100,100 as the first

point and 100,200 as the second point. This would place the copy 100 drawing

units above the first. Points can either be entered using the keyboard or by

clicking anywhere in the drawing. Shortcut "cp"/"co"

Mirror

Creates a mirror image of the selected object. The user defines two points, along

which autocad generates a "line of reflection" and the reflected object is

generated across this line with all components reversed. The user is then asked

if they want to keep or delete the original. One problem with the mirror command

is that if any text is included in the mirroring operation, it too is reversed making it

unreadable and ridiculous. To fix this, type "MIRRTEXT" at the command line

and change the value to 0. Shortcut "mi"

Offset

An offset is like a copy but is more precise and must be used for certain

situations as the result is likely to be slightly bigger or smaller than the original.

For example, consider a line that represents the edge of a road. This line

contains several curved segments, and you would like to make a copy of this line

to represent the opposite side of the road. A direct copy won't work, because the

radius of the inside of a curve is much tighter than on the outside. The offset

command allows you to simply define how far away and on which side you would

like the copy to be made, and AutoCAD will take it from there. Shortcut "o"

Array

An array is a quick way of doing a lot of copying, as long as all the copies are

arranged in a simplistic way. There are two types of array; polar and grid. For a

polar array, Autocad asks the user how many copies they want to make, and

requests a centre point and a number of degrees to fill. Autocad then sweeps

round this centre point making copies of the selected object in a circular pattern.

For a grid array, the user selectes how many rows and columns they require, as

well as the spacings between them and Autocad instantly duplicates the selected

object(s) as many times as necessary. Shortcut "ar"

Move

Works exactly the same as the copy command except the original is deleted.

Shortcut "m"

Rotate

The user selects the object(s) to be rotated, a centre point, and defines the

number of degrees to revolve through. The original is deleted, so if a copy is

desired the polar array tool should be used. (Though, since AutoCAD 2006, a

"Copy" option is included in this command, making it possible to retain the

original objects) Shortcut "ro"

Scale

The object(s) are selected, and a base point and scaling factor are defined. An

easy way of changing a drawing from metres to milimetres is to scale everything

up by a factor of 1000.

Drafting

Starting a drawing

Upon running the program, the user will likely be prompted with an option to open

an existing drawing or start afresh using a template. Templates are saved using

a DWT extension and provide a quick way to get started. Having selected a

template or having chosen to start from scratch, the user finds themselves at an

empty drawing and is free to input information. The main area of the program

window is taken up by the drawing area. This is surrounded by toolbars, a menu

bar and a command line. The toolbars and the menu bar work the same way as

other Windows programs, but the command line is a little more primitive. It is a

throwback to the earlier versions of AutoCAD which existed in a time prior to

Graphical User Interfaces and all editing had to be done by typing in commands

and specifying coordinates. Even something like zooming into an area required

the user to input the coordinates defining the window around the area to zoom

into. Naturally enough, none of this functionality has been removed, with the

result that AutoCAD now has both a modern graphical interface and a less pretty

but far more flexible command line system. The advantages of using the

command line to control the program will become clear later.

OSNAP Modes

Using object snap modes is crucial for accurate drawing. Drawing without them

will result in misaligned entities and inaccurate lengths and positioning.

They can be accessed while using a command that asks the user to input a

specific point, either directly at the command line, the OSNAP toolbox or by right

clicking while holding the shift key.

Layout Space/Model Space

Layout Space is typically used as an area for drawing entities that are not real-

world objects, but rather entities that are informational in nature (annotations,

border and title block, notes, etc.) and therefore can always be drawn at the

same size they will be printed at. It has been long-debated about the usefulness

of Layout(Paper) Space, especially since AutoCAD introduced xRefs and the

ability to clip them. Many users find working solely in Model Space an efficient

method of working in CAD (ala Microstation), however both methods of working

in AutoCAD have their pros and cons, and what method a user may choose will

largely depend on personal preference and/or the preferred method of the

company one works for.

Model Space

Model space is basically "the real world". Everything is drawn at a scale of one to

one (where meters, millimeters or inches are the preferred drawing units) and all

drawing components are positioned at the correct distances from each other,

regardless of what sheet of paper they may end up being printed on. The

drawings may also be positioned on a specific coordinate system, such as a

national mapping grid, in order to integrate accurately with other drawings.

Layout (Paper) Space

A typical Layout Space layout will consist of a standardized title block containing

information about the drawing; drawing number, date completed etc. This title

block will be drawn to accurately fit on a standardized sheet of paper. For

example, a sheet of ISO A1 measures 841mm by 594mm. Thus, a title block for

printing on such a sheet may measure 820 drawing units by 570. It can then be

printed out at a scale of 1 to 1, and will fit on the page nicely.

Viewports

All this is of course well and good, but how do we get the actual drawing

information from model space into this titleblock? To do this, we utilize an item

known as a viewport. A viewport is a shape (usually a rectangle but can be any

shape) that is drawn into paper space. Think of them as a TV screen. Inserting a

viewport into paper spaces "places a camera" into model space. You can change

the angle of view, the scale factor and many other variables in the viewport

settings. These changes only effect this one viewport. This lets you have, for

example, one large viewport of a building site at a scale of 1:100, and right

beside it another showing a detailed area at a scale of 1:10. It's the same

building site, and it exists only once in model space, but it is represented twice in

two different ways in the final drawing. The obvious advantage of this is any

changes made in model space will instantly update in every viewport, keeping all

your printable drawings up to date.