Chapter 5: Fundamentals IV

Advanced Drawing commands Advanced Object Selection Object Selection Methods Advanced Modify commands After completing this Chapter, you will be able to use the following features:

AutoCAD provides various drawing commands that make it possible to create geometric figures more easily and accurately. Donut Solid Point Sketch Advanced Drawing Commands

Donut The DOUGHNUT (or DONUT ) command draws solid-filled circles and rings by specifying outer and inner diameters of the filled area. The fill display depends on the setting of the FILLMODE system variable.

Solid The SOLID command creates a solid-filled straight-sided area whose outline is determined by points specified on the screen. Invoke the solid command by selecting 2D Solid from the Draw menu (Modeling submenu). Two important factors should be considered when using the SOLID command: (1) the points must be selected in a specified order or else the four corners generate a bowtie instead of a rectangle; and (2) the polygon generated has straight sides.

Point The POINT command draws points on the drawing, and these points are drawn on the plotted drawing sheet with a single “pen down.” You can enter such points to be used as reference points for object snapping (Node) when necessary. Points are entered by specifying coordinates or with the pointing device. Invoke the POINT command from the Draw toolbar.

When you draw the point, it appears on the display as a blip (+) if the BLIPMODE system variable is set to ON (default is ON). After a REDRAW command, it appears as a dot (.). You can make the point appear as a +, x, 0, or | by changing the mode from Point Style icon menu, invoked from Format menu.

Sketch The SKETCH command creates a series of freehand line segments. It is useful for free-hand drawings, contour mapping, and signatures. The sketched lines are not added to the drawing until they are recorded. The available options include: Sketch Pen eXit Quit Record Erase Connect

Various options available to control the appearance of objects during selection preview. You can make the changes to the appearance of the selection preview from the Visual Effect Settings dialog box (opened from the Selection tab of the Options dialog box). Advanced Object Selection

The group of objects selected for the modification is called the selection set. In addition to the basic selection methods (window, crossing, previous and last), following are the advanced object selection options available: Wpolygon selection similar to the Window selection, but it defined as a polygon-shaped window rather than a rectangular area. The polygon is formed as you select the points. The polygon can be of any shape but may not intersect itself. To select the WPolygon option, enter WP and press ENTER at the “Select Objects:” prompt.

CPolygon selection similar to the WPolygon selection, but it selects all objects within or crossing the polygon boundary. If there is an object that is partially inside the polygon area, then the whole object is included in the selection set. To select the CPolygon option, enter CP and press ENTER at the “Select Objects” prompt. Fence selection similar to the CPolygon option, except that the last vector of the polygon shape is not closed. The selection fence selects only those objects it crosses or intersects. Unlike the WPolygons and CPolygon, the fence can cross over and intersect itself. To select the Fence option enter F and press ENTER at the Select Objects: prompt.

Remove selection lets you remove objects from the selection set. The Select Objects: prompt always starts in the Add mode. The Remove mode is a switch from the Add mode, not a standard option. Once invoked, the objects selected by whatever and however many options you use will be removed from the selection set. It will be in effect until reversed by the Add option. Add selection lets you switch back from the Remove mode in order to continue adding objects to the selection set by however many options you wish to use. Single selection causes the object selection to terminate and the command in progress to proceed after you use only one object selection option.

Undo selection allows to remove the last item(s) selected from the selection set without aborting the Select Objects: prompt and then to continue adding to the selection set. It should be noted that if the last option to the selection process includes more than one object, the Undo selection will remove all the objects from the selection set that were selected by that last option. All selection selects all the objects in the drawing, including objects on frozen or locked layers. After selecting all the objects, you may use the REMOVE (R ) option to remove some of the objects from the selection set. The All option must be spelled out (All) and cannot be used as an abbreviation as you may do with the other options.

AutoCAD provides six selection modes that will enhance object selection. By having the appropriate selection mode set to ON, AutoCAD provides more flexibility and greater ease of use in the selection of the objects. Object Selection Methods

NOUN/VERB selection feature allows the traditional verb- noun command syntax to be reversed for most modifying commands. When the Noun/Verb selection is set to ON, objects are selected first at the Command: prompt and then invoke the appropriate modifying command to modify the selection set. To clear the current selection set, press ESC key at the Command: prompt. This clears the selection set, so any subsequent editing command will once again prompt for object selection. Use Shift to Add feature controls how objects are added to an existing selection set. When Use Shift to Add to selection is set to ON (default OFF), it activates an additive selection mode in which SHIFT must be held down while adding more objects to the selection set.

Press and Drag feature controls the manner by which the selection window is drawn with pointing device. When Press and drag is set to ON, selection window is drawn by holding down the pick button and dragging the cursor diagonally while the window is created. When it is set to OFF (default), need to provide two separate picks to create the selection window. Implied Windowing feature allows to create a selection window automatically when the “Select objects:” prompt appears. When Implied Windowing is set to ON (de-fault), the picks from left to right creates a window and right to left creates a crossing. If Implied Windowing is set to OFF, you can create a selection window by using the Window or Crossing selection set methods.

Object Grouping feature controls the automatic group selection. If Object Grouping is set to ON, then selecting an object that is a member of a group selects the whole group. Associative Hatch feature controls which objects will be selected when an associative hatch is selected. If Associative Hatch is set to ON, then selecting an associative hatch also selects the boundary objects.

AutoCAD not only allows to draw objects easily, but also allows you to modify objects. This section discusses seven important commands that will make your job easier: Lengthen Stretch Rotate Scale Pedit Join Match Properties Advanced Modify commands

Lengthen The LENGTHEN command is used to increase or decrease the length of line objects or the included angle of an arc.

D elta selection changes the length or, where applicable, the included angle from the endpoint of the selected object closest to the pick point. A positive value results in an increase in extension; a negative value results in a trim. Percent selection sets the length of an object by a specified percentage of its total length. It will increase the length/angle for values greater than 100 and decrease them for values less than 100. Total selection changes the length/angle of an object to the value specified. Dynamic selection changes the length/angle of an object in response to the cursor’s final location, relative to the endpoint nearest to where the object is selected. Available options include:

Stretch The STRETCH command stretchs the shape of an object without affecting other crucial parts that remain unchanged. The STRETCH command moves the endpoints that lie inside the window, leaving those outside the window unchanged.

Rotate The ROTATE command changes the orientation of existing objects by rotating them about a specified point, labeled as the base point. By default, a positive angle rotates the object in the counterclockwise direction, and a negative angle rotates in the clockwise direction.

Scale The SCALE command lets you change the size of selected objects or the complete drawing. Scale factor is applied to the X, Y, and Z directions. To enlarge an object, specify a scale factor greater than 1. To reduce the size of an object, use a scale factor between 0 and 1.

Modifying Polylines The PEDIT command modifies polylines. It has special editing features for dealing with the unique properties of polylines and is perhaps the most complex AutoCAD command, with several multioption submenus totaling some 70 command options.

When AutoCAD prompts to select an object and if you select a line or an arc instead of a polyline, you are prompted as follows: Object selected is not a polyline. Do you want it to turn into one? Responding Y turns the selected line or arc into a single-segment polyline that can then be edited. Normally this is done in order to use the Join option to add other connected segments that, if not polylines, will also be transformed into polylines. The second prompt does not appear if the first segment selected is already a polyline.

After the object selection process, AutoCAD returns to the multi option prompt as follows: Enter an option: (select one of the available options from the shortcut menu) Close selection performs in a manner similar to the Close option of the LINE command. Open selection deletes the segment that was drawn with the Close option. Join selection takes selected lines, arcs, or polylines and combines them with a previously selected polyline into a single polyline if all segments are connected at sequential and coincidental endpoints.

Width selection permits uniform or varying widths to be specified for polyline segments. Edit Vertex selection modify vertices of polylines in several ways – Break, Insert, Move, Straighten, Tangent and changing width of selected segment. Fit Curve selection draws a smooth curve through the vertices, using any specified tangents. Spline Curve selection provides several ways to draw a curve based on the polyline being edited. These include Quadratic B- spline and Cubic B-spline curves. Decurve selection returns the polyline to the original status. Undo selection reverses the latest PEDIT operation. Exit selection exits the PEDIT command.

Joining Similar Objects The JOIN command allows you to create one line, arc, elliptical arc, polyline, or spline from multiple like objects.

Match Properties The MATCHPROP command allows to copy selected properties from one object to one or more other objects located in the current drawing or any other drawing currently open. Properties that can be copied include color, layer, linetype, linetype scale, lineweight, thickness, plot style, and in some cases, dimension, text, table, and hatch. Invoke the MATCHPROP command by selecting Match Properties from the Standard toolbar.

Properties settings dialog box