AutoCAD is the engineer’s and architect’s best friend. It is a Computer Aided Design (CAD) program created by Autodesk, and first released way back in 1982, and is currently in its 18th generation (if you happen to have an older version, we have one course that will familiarize you with AutoCAD 2010 and another that will help you with the 2013 version). It started out using simple lines and circles, along with text overlays, to help design buildings, public spaces, and products, and has evolved to include advanced 3D tools which allow the user to more fully explore their creation, with high-quality, fast-moving rendering. We have many courses in AutoCAD: including this one, that teaches you the basics of drawing, and this course, which tells you all about modeling and rendering.
The most basic building blocks of AutoCAD are called “entities”, and they are created within the program with the purpose of being manipulated and changed to meet the needs of the user and to help them create the designs they see in their head. These entities are manipulated through the use of commands, which we will be discussing today. Some commands can be used at any time, others, only at specific junctures in the creation process. If you’re brand new to AutoCAD or need to brush up, this article discusses the basics of AutoCAD in four simple steps.
Commands for Setting the Drawing Environment
These commands may be used at any time, but are mainly called upon more during the beginning of the drawing process.
- Units: Specifies the display format and precision. This command dictates whether the units are displayed as decimals or as a fraction, as well as how many decimal places the number will go. Also specifies how angles will be represented, either as decimal degrees, radians, etc., as well as how angles will be measured, i.e. clockwise vs. counterclockwise.
- Limits: Sets limits to the boundary and size of the current drawing. The user must specify the lower left-hand corner and the upper right-hand corner. This setting may be turned on or off – when on, points may not be specified outside the currently set limits.
- Qtext: Quick text – may be turned on or off, like the Limits command. When switched on, text is displayed in rectangles, showing the extent of the text. When off, just the text is displayed, without the rectangle.
- Viewres: Performs two functions: first, it lets the user disable fast zoom, which makes sense when conforming a more modern version of AutoCAD to an earlier one that lacks the fast zoom capability. Second, Viewres allows the user to control the smoothness and speed of circles and arcs drawn in the display. The user does this by choosing the number of sides circles will have. It is recommended this value be set at 2000.
- Blipmode: Blips are small crosses used to mark screen positions that the user has pointed to. They can be useful reference points, but too many of them can crowd the screen, making it difficult for the user to see. Engaging Blipmode allows the small crosses to stay up in the wake of the pointer, and turning it off makes them disappear. Blips are not part of the final drawing and are removed when the drawing is complete.
- Fill: When this command is engaged, solids, traces, wide polylines, and donuts that are drawn are then filled in with color, as opposed to just being outlines. This command does not affect the drawing’s plotted output, and, when using this command, there is a trade-off between regeneration time and the image’s quality.
- Status: This command simply lists, on the Text Screen, the current drawing environment, the modes, and statuses that are engaged for this drawing.
Commands for Drawing Entities
Once the drawing environment has been set, these commands are used to actually draw the entities.
- Line: Allows for the sequential drawing of one or more straight lines. Once engaged, this command elicits a prompt of “From point:”, at which point the user specifies a starting point for a line, or they may press RETURN, which starts the line at the end of the previous line or arc that was drawn. Next, the prompt “To point:” is displayed, allowing the user to specify a sequence of points to which the line will extend. They may also type the letter C to close the polygon, or the letter U to undo the previous line segment, or they may simply press RETURN to complete the command.
- Point: Draws a single marker/point, which is, by default, a single dot, but may be changed to something else if desired.
- Circle: Draws a circle by letting the user specify the center point, then dictating the circle’s size by entering a value for either the circle’s radius or its diameter. Another option to creating a circle with this command is to specify three points on the circle’s circumference, two end-points of its diameter, or its radius along with two other lines or circles to which the new circle will be tangential.
- Arc: This command draws arcs, and, like circles, may be dictated in one of several ways. The various methods for constructing arcs with this command are as follows: (1) specify three different points, (2) starting point, center, and end point, (3) starting point, center, and included angle, (4) starting point, center, and length of chord, (5) starting point, ending point, and radius, (5) starting point, ending point, and included angle, (6) starting point, ending point, and starting direction, and finally, (7) starting point and direction of previous line or arc, plus ending point.
- Ellipse: Ellipses are constructed by specifying the two end points of one of the major or minor axes, followed by a distance value defining half the length of the other axis.
- Pline: Draws 2D polylines, which are continuous sequences of straight lines and/or arc segments with varying line length, dictated by the user. You are able to close a polyline to form a polygon. This course on AutoCAD 2D fundamentals will help you navigate the Pline command and others. It also may be helpful to know that polylines may be exploded into separate line and arc entities if necessary.
- Polygon: Draws regular polygons by entering the number of edges, then specifying the shape’s center and radius, or by locating the endpoints of any of its edges. Once created, polygons are to be treated as closed polylines.
- Hatch: Within one or many closed boundaries, a cross-hatch pattern may be created with the Hatch command. The boundaries must be well-defined, otherwise, the cross-hatch may leak out unexpectedly. The user may select pre-determined patterns supplied by AutoCAD, or they may enter their own and add them to the set that’s already there.
- Bhatch: A newer command in the AutoCAD quiver, it helps the user to better use the previously discussed Hatch command. It supports boundary hatching, allowing the user to pick a point that is adjacent to the boundary they wanted, and this new command lets AutoCAD search for the nearest entity, then constructs a closed boundary by tracing in a counterclockwise fashion to look for intersection points as well as connecting lines or arcs. Bhatch is convenient in that it allows the user to preview adjustments without having to start over each time.
- Dtext: Allows you to draw text dynamically, changing text height and rotation, allowing it to be moved, centered, stretched between two points, aligned, overscored, underscored, have symbols added, fonts changed, etc.
These are some basic and useful commands that may be used more than other more specific commands.
- Redraw: Refreshes the program and re-displays the graphics on the screen, but without extraneous graphics, such as blips, that may have been left behind from earlier operations.
- Save: Saves all current changes and drawings to be saved to the disk. As with any important project done on a computer, it’s best to get into the habit of saving regularly, especially during long drawing sessions, to prevent any work from being lost.
- End: Finishes the current session, saves the work, and takes you back to AutoCAD’s main menu.
- Quit: Finishes the current session, but does NOT save the changes that were made to the current drawing, then returns you to the main menu.
Drawing and Manipulation Commands
These commands alter your drawings, allowing you to enlarge and reduce views, maintain graphic accuracy, and manipulate space and viewports, among other things. These commands, taken in conjunction with this course on the editing essentials of AutoCAD, will make you an expert ASAP.
Moving Around the Drawing Area
- Zoom Scale: Allows the user to enter a magnification or reduction factor. Numbers less than 1 will reduce the drawing, those greater than 1 will expand it. The Zoom Scale amount is applied to the entire drawing, and doesn’t change the actual size of the entities, simply the magnification.
- Zoom Extents: Commands AutoCAD to display all of the current drawing’s graphics, using the largest possible image, not necessarily extending it to the user-defined limits.
- Zoom All: Displays the drawing to the drawing limits.
- Zoom Window: Prompts the user to define which part of the drawing is to be magnified, by defining the lower left-hand and upper right-hand corners of the box to be zoomed in on.
- Zoom Center: The user enters a point, which the program uses as the center of an area to be magnified, then they enter a value to be applied to the new, magnified image’s height.
- Zoom Left Corner: Like Zoom Center, the specified point is the lower left-hand corner of the new display.
- Zoom Previous: Commands the program to revert back to the prior view displayed. Up to five views may be stacked up for comparison.
- Zoom Dynamic: The most powerful of the Zoom options, it allows for quick movement around the drawing.
- Pan: Permits panning across the current drawing without changing the scale.
- Vpoint: Establishes a viewpoint from anywhere in space, which may be entered as a 3D point, a spherical point, or dynamic (simply press RETURN instead of entering a specific point). This course will show you how to master AutoCAD’s 3D capabilities in four hours.
- Dview: Provides a dynamic tool for viewing an object in 3D as either a parallel projection or a perspective. Using a camera along with target concept, AutoCAD is able to manipulate the viewing position, direction of view, focal length, and viewing distance.
- Plan: Puts the user back in plan view when done working in 3D.
Model Space, Paper Space, Viewports
- Tilemode: Switching Tilemode to off (setting the value to 0), turns AutoCAD to paper space. Setting the value to 1, AutoCAD switches to model space.
- Vports: Only available when Tilemode is on, it allows the user to establish up to 16 viewports on the screen, so that each one holds a different view of the drawing. You are able to work in only one viewport at a time, but may easily move among the different ones.
- View: Saves the current view under a name the user specifies, or restores a previously saved view, and may be used in model or paper space,
- Mview: Used when Tilemode is off, Mview creates and defines various viewports’ characteristics while in paper space. They may be turned on and off and linked with views that have been previously saved with the previous View command.
- Mspace: Also used when Tilemode is off, this command allows the user to switch to model space, then edit their drawing inside a paper space viewport.
- Pspace: With Tilemode off and model space active, the user may switch back to paper space and edit graphics.
- UCS: The User Coordinate System (UCS) is set up to be positioned and oriented anywhere in 3D space. After the UCS is implemented, the previous 2D drawing is now done in the X-Y plane of the new UCS. The user is now able to easily draw anywhere in space, and also aids when drawing in 2D.
- Snap: Sets up a grid that is both invisible and orthogonal, square or rectangular, which all points entered with the mouse may be locked onto.
- Grid: This command sets up a visible grid of white dots that is used for referencing purposes.
- Axis: Similar to the Grid command, except the white dots are replaced with two intersecting axes with tick marks.
- Ortho: When turned on, Ortho mode makes all lines drawn with the mouse parallel to the axes.
- Osnap: (Object Snap) In Osnap’s “Running Mode”, it allows points to be precisely located on reference points of existing objects. They may be overridden by selecting different object snap modes for a specific entry.
- Aperture: Sets the size of the Osnap target box, where values ranging from 1-50 screen units are valid.
Only two commands are in this group, used to delete objects and entities.
- Erase: This removes a selected group of entities, which may be entered before or after the command itself is entered.
- Oops: Restores the most recently deleted object group from using the previous Erase command. This command may not be repeated, as it only restores one group of deleted objects.
The following group of commands allows the user to select a group of objects that need to be transformed in one way or another.
- Move: The user may dictate the direction and length of a move of specified objects by indicating two points which define a vector between the objects.
- Copy: Similar to the Move command, Copy does not affect the original group of objects, with the copied objects being completely independent of the original objects.
- Rotate: Providing a specific base point and angle, the user may rotate an object of their choosing with this command. Negative angles will provide a clockwise rotation, while a positive angle gives a counterclockwise rotation.
- Scale: Enlarge or shrink a selected group of objects by selecting a base point for the scaling as well as applying a factor for which to scale.
- Mirror: This command produces a mirror copy of a selected object group by specifying the two ends of the mirror line. Then, the mirrored objects may be deleted or kept, depending upon the user’s preference.
- Stretch: Allows the user to move a portion of a drawing while retaining its connections to other parts of the drawing, thus stretching it out. Blocks, Hatch patterns, and Text entities may NOT be stretched.
- Array: Produces multiple copies of selected objects that are arranged in a rectangular or circular pattern.
- Offset: Constructs a new entity parallel to an existing one. This could be a single line, polyline, arc, circle, or curve.
Error Recovery Commands
These commands bring back errors made during the editing process.
- U: The U command undoes the most recent drawing or editing and may be used repeatedly, all the way back to the beginning of the session.
- Redo: This command is used immediately after an error to redo what was undone.
- Undo: This is like the U command but a bit more complicated. It is able to undo several commands at once, allows the user to set mark points and later undo back to those points, and to group operations together and undo them simultaneously.
Commands that Change Existing Entities
These commands allow different editing changes to be made to existing entities.
- Change: This command covers a lot of ground, with two basic main capabilities: first, use this command to change properties that all entities possess, for example, layer name, color, line type. Second, change the geometry and attributes of specific types of entities.
- Pedit: This is the command used to make changes to polylines, such as width, taper, closing an opening, breaking one into two, moving, adding, and deleting vertices, etc.
- Break: This command splits an already existing line, arc, circle, or polyline into two separate parts, producing an erased portion in between them.
- Trim: This command trims parts of certain objects in a drawing in order to finish them precisely at some cutting edge (or edges) that are established by one or more other objects. One or several lines, arcs, circles or polylines must first be identified to serve as cutting edges, which may be selected by any of the methods available. Next, pointing is used to select the parts of the objects that are to be trimmed. Many objects may be selected in this way for trimming, including ones that had been specified as cutting edges.
- Extend: Complementing the Trim command, Extend operates similarly, but the selected lines are extended to end exactly at the specified boundary edges.
- Fillet: This command connects two existing lines, circles, or arcs by adding an arc with a specific radius (a fillet), and allows the user to change the current default radius prior to filleting.
- Chamfer: Like the Fillet command, this one chamfers, or cuts away, as in carpentry, corners with a straight edge.
- Divide: Divides an object into a specified number equal parts, from 2 to 32,767 parts.
- Measure: This measures an object, from one end to the other.
This final group of AutoCAD commands are used to obtain information a drawing’s object’s position and nature.
- List: Lists stored information about any selected entities found within the current drawing.
- Dist: Calculates and displays the distance and angle between two points in a drawing.
- Area: Calculates and displays any region’s area and perimeter, as long as it is defined by a sequence of specified points on the drawing, as long as they form a closed polygon.
A lot of information? Absolutely! But then again, AutoCAD is a lot of program, and these commands are essential in getting the most out of it. If you’d like to bolster your new found command of these AutoCAD commands, we have a course that will help you fill in the missing pieces of your AutoCAD education, and if you’re short on time, this AutoCAD crash course will get you operational in no time flat. The AutoCAD website also provides an overview of this expansive program which may help to answer any questions you may have after taking in all this information.