AutoCAD Drawing and model space
All AutoCAD drawings are composed of lines, which can either be straight or curved (arcs).
AutoCAD has 4 main types of straight lines:
At first glance, using the Line tool and the Polyline tool might seem to yield the same results. There is an important difference between the two however: the line tool creates separate objects (line) between each point, opposed to the Polyline tool which creates one object consisting of multiple points (and segments). Even though this might seem like a small difference, it's important to use Polylines where possible in your drawing, as it helps you to keep a clear overview of your drawing (no confusing individual lines) and makes it easier to export you drawing to other programs.
You can try each line tool by clicking the point in the model space. A little further down, we'll see how you can draw lines accurately using coordinates and snap options.
There are 3 main types of Curved lines:
You can use these tools in the same way as you would the straight lines. The difference being, that these tools might prompt you to select a center point instead of a starting point.
Drawing using coordinates
To quickly draw a line, select the Polyline tool and click on the desired start and end points of the line.
The PolyLine tool will stay active, so when you click on a third point, AutoCAD will draw another line between the second and third point.
You can close the Polyline tool, just like any other tool in AutoCAD, with [enter] or [space].
However, this way of constructing your drawing is rather inaccurate. And it's therefore recommend that you either use the snap tools or coordinates to create your drawing.
When using coordinates, you can either specify absolute or relative coordinates. Absolute coordinates relate to the origin, in this case being (0,0). Relative coordinates relate to another point, for instance, the endpoint for a line can be given relatively to its starting point.
To create a line with a length of 2000 mm (units), you start by specifying a starting point. Next, enter ' 0,2000 ' and finish by pressing [enter] or [space]. When not using dynamic input, put an @-sign in front of the numbers, to indicates your using relative coordinates.
When using absolute coordinates, you can specify both start- and endpoint. Select the line tool and enter the coordinates, e.g. '200,5000'. The staring point of the line will be 200 right and 5000 units above the origin.
You can also use rotation angles to accurately draw lines. After selecting a start point for the Polyline, AutoCAD will show information about the size and angle of the line:
After you've set the length of the line (for instance 250) press [Tab] and AutoCAD will instantly jump to the angle input:
Now input the desired angle (0 to 360) and finish with [space] or [enter]
If we want to create a circle with a diameter of 750, we first need to select a center point. After we've selected the center point, the command bar will look like this:
As we can see in the command bar, AutoCAD is asking if we want to input a diameter or a radius (Right now the input is set to radius) In our case we want to change the input from radius to diameter, because we want a circle with a diameter of 750.
To achieve this, we need to pres [d] (the first letter of Diameter)
Now all we need to do is type 750 and press [enter] or [space]
The Arc tool works a little differently from the other curved line tools; instead of using a center point, it uses three separate points to determine its shape.
If you look in the command bar, after selecting the start point of the arc, you can see that AutoCAD gives you 3 options:
You can either specify the second point in the view screen, or you can use the option 'Center' or 'End' by typing there respective first letter.
For instance, if you want to specify the center point instead of the second point, type 'c' in the command bar.
Now you'll be able to specify the center point:
Using OSNAP (object snap)
Making an accurate AutoCAD drawing by coordinates is possible, but it's very time consuming. In most cases it's therefore recommended to use AutoCAD's snap options.
You can turn the snap options on by pressing the OSNAP button in the status bar:
This makes certain points on a line 'magnetic'. As a default, these points are the start and end point of a line.
With OSNAP on, the crosshair automatically jumps to such a point as soon as you get near to it. This makes accurately connecting different lines to each other much easier.
Whilst making your drawing, you may want to connect a line to a different point other than the end or start point. To be able to do this, you'll need to adjust the OSNAP settings by right clicking on OSNAP > Settings.
The following screen will appear:
Endpoint and Center are checked by default, but some other useful snap options are Midpoint (to snap to a midpoint of a line), Perpendicular and Intersection.
If we want to make use of the perpendicular snap option, we first need to check the checkbox:
Now if we want connect a line to another line at an angle of 90 degrees, we first select the start point and then drag the second point toward the line until the orange perpendicular icon appears:
Now we only have to make a left mouse click and we've got a perfect perpendicular connection of 2 lines.
Using the snap options makes accurately connecting lines very fast and simple, this however, still necessitates us to use coordinates to accurately position lines relative to each other.
Fortunately AutoCAD has a powerful feature to aid us with positioning lines, called OTRACK (Object Snap Tracking). To enable this function press the OTRACK button in the status bar:
When drawing with OTRACK enabled, AutoCAD will relate to existing line's in your drawing.
We want a line to start at the following location:
Without OTRACK we would need to calculate and manually input the coordinates. But with the use of OTRACK we can do this much faster.
First, select the polyline tool and move over the existing endpoint:
An orange square appears, indicating that it's possible to snap to that endpoint.
As we move the cursor upward, the square changes into a square with a cross (+) and an alignment path (the dotted line) appears:
Now we just need to select the second tracking point by moving the mouse over the upper left corner of the rectangle:
A second cross (+) appears on the rectangle and, as we move the mouse to the left, an intersection of 2 alignment path appears (represented by an 'x').
Confirm the start point of the polyline by pressing the left mouse button.
OTRACK works in conjunction with OSNAP, be sure to turn them both on!
POLAR is a very handy option in AutoCAD that helps you to quickly draw orthographic lines. Opposed to ORTHO which only allows you to draw orthographic lines, POLAR still gives you the freedom of drawing at all angles, but also gives the possibility to quickly draw orthographic lines with the help of an alignment path.
Let's first turn POLAR on in the status bar:
If we now use the polyline tool to draw a line, we can freely position the line, but there also appears an alignment path when we try to draw an orthographic line:
We could now input the length of the line, for instance 300 and execute by pressing [enter] or [space]
In essence, polar uses it’s own start point as a tracking point
POLAR also works really well with OTRACK and OSNAP, so make sure you have all those options enabled.
if we look at where we left of in the OTRACK example, we can see that we've selected a starting point for our line, but we still have to position the end point:
Now if we would want to draw an orthographic line, we could use one of the existing lines as a reference point. It's easier however to enable POLAR in the status bar. Now we're able to directly draw an orthographic line:
Because we've got OTRACK and OSNAP enabled we can use the uppermost line as reference:
Now just click the left mouse button, and we're all done:
While working with AutoCAD you probably noticed that your cursor continually gives you information, for instance the length and angle of a line:
If you don't want to have al this information in your view screen, it's possible to turn dynamic input off by clicking on the DYN button:
Our cursor now looks like this:
Even though this might give you a 'clean' workspace, working without dynamic input as some distinct disadvantages.
Besides the lack off information, AutoCAD does not automatically recognize when to use relative coordinates or absolute coordinates.
So if we want to input relative coordinates, we need to type an '@' symbol in front of the coordinates: @1000,500
When using absolute coordinates, we do not need to use the '@' symbol and we can directly type the coordinates: 4000,800
If we want to draw a line at an angle we first need to type the length of the line, an '<' symbol followed by the desired angle: @1000<45
You can turn dynamic input on again by pressing the DYN button.
When you're using Dynamic Input, all coordinates are assumed to be relative coordinates.
If you want to specify an absolute coordinate (such as 0,0), enter #0,0.When you want to specify a point at a relative distance and a specific angle, such as 200 units at 30 degrees, enter: <30,200