The Basic Elements of AutoCAD 2 (Part 1): Basic Geometry

Previously, we deep-dived into the toolbar applications of Autodesk's engineering drawing application, AutoCAD. In this article, we take a step ahead and explore how to make lines and polylines using these toolbar options. 


Why Learn Geometric Commands in AutoCAD?

The fundamental purpose of using AutoCAD is to create lines, arcs, circles, and other geometric shapes that are necessary for the phase of producing clean drawings that are free from errors.  

Even if you are modeling in three dimensions for computer-aided design with AutoCAD, you would need to create accurate two-dimensional shapes. You can only convert your designs to 3D objects by extruding, lofting, and more if the 2D models are correctly made. 

In essence, the basic geometry commands will help you in creating the shapes that would form the skeleton of our drawing. As such, students must learn about and become proficient in these AutoCAD functions. 

With that, let's get into drawing lines in AutoCAD.


The first tool that we will explore is the LINE tool in the AutoCAD desktop application.   

The LINE tool creates straight line segments. With LINE, you can make a series of lines that are parallel, collinear, intersecting, and more. Every line segment you create using this tool can later be edited separately.  


How to Draw a Line

In the application, navigate to the HOME tab in the AutoCAD toolbar. Here, you will notice that the first icon represents the LINE tool.

When you click on the LINE icon, you will be prompted by AutoCAD to specify the first point. You can either specify the point by typing the coordinates or by clicking anywhere in the model space. Similarly, the second point can be specified.  

You can even create line segments at any angle by manipulating the numbers in the boxes that appear by pressing TAB on the keyboard.  


Important Features in AutoCAD

  • Object Snap: Once you have created a line segment and attempt to create another one, you can see that when you bring the cursor close to the first line segment's endpoint, it automatically snaps to the endpoint of that line. This feature of AutoCAD is known as the object snap feature.


  • Polar Tracking: When you get closer to the multiples of 45 degrees in the model space while drawing the line segment, you can see that the line is snapped at that angle, and green dotted lines appear. This feature is known as polar tracking in the application.


Feature Controls

To control the polar tracking and object snap features in the AutoCAD application, head over to the customization tab by clicking on the icon with three parallel lines on the bottom right-hand side corner of the screen.  

Additionally, you can even toggle these from the bottom customization toolbar directly. The icon will be represented by a square and highlighted in blue if the feature is on. 


Customizing Object Snap

By clicking the customization icon, you can specify a particular instance where you want the object to snap. If you want to snap to the mid-point of a line segment, for instance, you can toggle that option on. 

You can even choose to snap to these parts of a line: 

  • Endpoint
  • Centre
  • Geometric Centre
  • Node
  • Quadrant
  • Intersection
  • Extension
  • Insertion
  • Perpendicular
  • Tangent
  • Nearest
  • Apparent Intersection
  • Parallel


Customizing Polar Tracking

Similar to object snapping customization, you can even customize the polar tracking feature. If you do not want AutoCAD to snap at multiples of 45, you can click on the customization toolbar at the bottom of the screen (represented by a circle with an angle symbol). 

Clicking on the button will provide you with a host of options like: 

  • 90d0'0"
  • 45d0'0"
  • 30d0'0"
  • 22d0'0"
  • 18d0'0"
  • 15d0'0"
  • 10d0'0"
  • 5d0'0"

For example, if you choose the 30d0'0" option, then you will be able to snap at angles that are multiples of 30 degrees, like 30 degrees, 60 degrees, 90 degrees, and so on.  

But if you want a quick way to snap at multiples of 90, then you can turn on the orthogonal mode in AutoCAD. You can toggle this by clicking on the button to the left of the polar tracking icon in the customization toolbar. 

This feature is useful when you are creating floor plans, walls, and other such perpendicular elements in the model space. 



A polyline is a chain of line segments for a single planar object. By using this tool, you can create straight-line segments, arcs, segments of arcs, and more.  


How to Draw a Polyline

When you select the tool, you will be prompted to select a starting point, just like in the LINE tool. After selecting the starting point, you can create a line segment and continue extending it in various directions, thus creating a polyline.

Plus, it need not necessarily be only a series of line segments. You can choose an arc from the top application toolbar at any point in time. This icon allows you to continue drawing in the model space without any loss in continuity.  

Another way to switch between the various shapes while using the POLYLINE tool is by right-clicking anywhere on the screen to open up a new menu. This menu contains the following options: 

  • Enter
  • Cancel
  • Recent Input
  • Arc
  • Close
  • Half Width
  • Length
  • Undo
  • Width
  • Snap Overrides
  • Pan
  • Zoom
  • Steering Wheels
  • Quick Calculator


The LINE tool allows you to select each individual line segment after drawing. However, the POLYLINE tool lets you select the entire two-dimensional profile in the model space. 


These were some important points about the LINE and POLYLINE tools that help engineers create geometric computer-aided designs using AutoCAD. We will look at circles and arcs in the next chapter.

AutoCAD is a widely used application that enables error-free drawings and 3D modeling. If you are a mechanical, automobile, or aerospace engineer, learning about this software is essential for a promising and successful career.

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