MODIFYING OBJECTS IN AUTOCAD

When creating technical drawings, once certain geometry is created it can be reused to build other related geometry. The modify tools will then be used to adjust this geometry to suit its purpose.

Offset

Use the Offset tool to copy lines, arcs and circles parallel to an original object.

The Offset tool can be accessed from the Ribbon Home tab > Modify panel.

Command line: To start the Offset tool from the command line, type “O” and press [Enter].

Clicking the Offset tool will prompt you with: Specify offset distance or [Through/Erase/Layer] <10.00>:

A distance can be entered in the command line or two points can be clicked on the screen to identify the distance. Once a distance has been specified, an object can be selected to offset and the side you wish to offset too.

Additional options are shown on the command line in the square brackets ‘[ ]’ and can be invoked by typing the capital letter.

Through is used to offset an object to align with other geometry in the file. The example below shows a line being offset and aligned with the endpoint of other geometry.

Erase will erase the source object on completion of the Offset command.

Layer allows the offset geometry to be created on a specific layer

Once a distance has been entered and the object has been selected, additional options are shown on the command line in the square brackets ‘[ ]’ and can be invoked by typing the capital letter.

Specify point on side to offset or [Exit/Multiple/Undo] <Exit>:

Exit will exit the command

Multiple allows offsetting the same object multiple times using the same offset distance. Each click will create a new offset.

Undo will undo the last offset.

Trim

The Trim command is a tool which removes parts of an object intersecting with other geometry.

Access the Trim tool from the Ribbon Home tab > Modify panel.

Command line: To start the Trim tool from the command line, type “TR” and press [Enter].

Clicking the Trim tool will prompt you with:

Select cutting edges... Select objects or <select all>:

You can now select the objects you wish to trim too also referred to as the cutting edges. As an alternative to selecting the objects, pressing [Enter] on the keyboard will select all objects in the file.

Once the cutting edges have been selected, additional options are shown on the command line in the square brackets ‘[ ]’ and can be invoked by typing the capital letter.

Select object to trim or shift-select to extend or [Fence/Crossing/Project/Edge/eRase/Undo]:

Fence uses drawn a line through the geometry that you wish to trim to the selected cutting edge. Any objects that the line intersects will be trimmed.

Crossing forces the selection window to be Crossing type on both sides of the cursor. (For more information on Crossing Window see module 04-Manipulating Objects)

Edge can be set to Extend or No extend. It allows you to specify whether the geometry will be trimmed back to the nearest intersecting edge or to an implied edge that would intersect the geometry if it were extended. If the Edge option is chosen, you will be prompted with:

Enter an implied edge extension mode [Extend/No extend] <Extend>:

Extend will trim to the nearest implied edge. Where the geometry doesn’t intersect, AutoCAD will trim to the point where, if extended, the geometry would intersect

The No extend option will trim to the nearest intersecting edge.

eRase will delete geometry without exiting the command.

Undo will Undo the last trim action.

Note: Holding the [shift] key whilst trimming reverses the functionality and extends a line or arc to the next object in its path instead of trimming.

Extend

The extend tool functions in a similar way to the trim command. The tool extends a line or arc to meet other objects.

To extend an object, from the Ribbon Modify tab > Modify panel, expand the Trim button and click the Extend tool

Command line: To start the Extend tool from the command line, type “EX” and press [Enter].

Clicking the Extend tool will prompt you with:

Select boundary edges... Select objects or <select all>:

You can now select the objects you wish to extend too. As an alternative to selecting the objects, pressing [Enter] on the keyboard will select all objects in the file.

You will then be prompted on the command line with:

Select object to extend or shift-select to trim or [Fence/Crossing/Project/Edge /Undo]:

The object to extend can now be selected. When an object can extend in multiple directions, clicking on the relevant side will extend that side of the object.

Note: Holding the [shift] key whilst extending reverses the functionality and trims a line or arc to the next object in its path instead of extending.

Explode

The Explode tool is used to break joined geometry such as Polylines and Blocks into individual objects.

A Polyline can be identified by selecting a shape, if connected lines also select, the shape is a Polyline. A polyline may need to be changed into individual segments when using tools such as offset where just a single segment is required.

The Explode tool can be accessed from the Ribbon Home tab > Modify panel.

Command line: To start the Explode tool from the command line, type “X” and press [Enter].

Clicking on the Explode tool will prompt you with:

Select objects:

The objects you wish to Explode can now be selected. Once completed, the shape will be individual entities.

Note: Exploding geometry can be useful but caution should be used. Joined geometry is easier to work with and more efficient in AutoCAD files.

Polyline Edit

A Polyline is a multi-segment line. A Polyline can be identified by selecting a shape, if connected lines also select, the shape is a Polyline

Lines can be converted to Polylines using the Pedit tool. Polylines keep geometry tidy by joining lines and arcs and they simplify geometry in the drawing. This makes editing easier because a change can be made to the whole Polyline without having to select multiple objects.

The Pedit tool can be accessed from the Ribbon Home tab > Modify panel by clicking on the Modify panels title to show the expanded Modify tools.

Command line: To start the Polyline Edit tool from the command line, type “PE” and press [Enter].

Clicking the edit tool will prompt you with:

Select first Polyline:

An existing Polyline, Line or Arc can be selected.

If you select a line or arc, you will be prompted: Do you want to turn it into one? You must convert to Polylines in order to apply the Pedit tools. At the command prompt, type “Y” for yes and “N” for no and press [Enter] to turn the object into a polyline.

Once an initial Polyline has been selected, the Polyline options are shown on the command line in the square brackets ‘[ ]’ and can be invoked by typing the capital letter.

Enter an option [Close/Join/Width/Edit vertex/Fit/Spline/Decurve/Ltype gen/Reverse/Undo]:

Close will join the ends of a Polyline to create a closed shape. If the ends don’t meet, a new segment is created to join them. If the Close option is used on a single segment, the resulting geometry will be two lines over each other.

Join is used to add existing line and arc segments to a Polyline. Each segment that you wish to join must touch the end of the previous segment. Where two segments of line touch the end of another segment, AutoCAD will join the segment that was created first. You cannot join more than a single segment to another segment.

Width modifies the thickness of a Polyline. The thickness shouldn’t be confused with lineweight. A lineweight is the thickness printed, a Polyline Width is a physical thickness, Width is useful for filling walls with a solid colour such as partition layouts.

Edit vertex allows the addition and removal of vertices from an existing polyline. Using the Edit vertex tool gives additional options for inserting and removing vertices.

Fit changes a Polyline from straight segments to a spline which passes through the points of the original Polyline using the smoothest curve possible.

                         

Spline changes a Polyline from straight segments to a spline whose control points are on the vertices of the original Polyline.

                      

Decurve will change a Polyline that has had the Fit or Spline features applied, back into straight segments.

Ltype gen controls whether Linetypes are applied to individual segments of a Polyline or to the polyline as a whole. This can be useful to obtain a uniform Linetype across a single Polyline.

Reverse reverses the start and end points of a line. This can be useful when a linetype has letters in order to get the letters to display backwards or inverted.

Undo undoes the last Polyline action.