learning objectives - los rios community college...

Splines

Learning Objectives

After completing this chapter, you will be able todo thefollowing:/ Use the MLINE command to draw multilines.

/ Create your own multiline styles with the MLSTYLE command./ Edit multiline intersections, corners, and vertices./ Draw and edit spline curves.

This chapter explores drawing and editing AutoCAD multilines and splines.Multilines are combinations of parallel lines consisting of up to 16 individual linescalled elements. You can offset the elements as needed to create a pattern for any fieldof drafting, such as architectural, schematic, or mechanical. Multilines are drawn usingthe MLINE command and its options and are modified using the MLEDIT command.

A spline is a special type of nonuniform curved line. The SPLINE command isused to create true splines. Splines can be edited using the SPLINEDIT command.

C Drawing Multilines j>The MLINE command is used to draw multilines. To access the MLINE command,

pick Draw > Multiline or type ML or MLINE. The prompts and options for the MLINEcommand are similar to those for the LINE command. You can use the Close option atthe last prompt to close a polygon. Enter Uduring the command sequence to undo thepreviously drawn multiline segment.

A multiline configuration, or style, can be set using the MLSTYLE command. Thedefault AutoCAD multiline style has two elements and is called STANDARD and consistsof two parallel lines. If you pick on one line to display grips, you can see that the enteredcoordinates correspond to both lines. Multiline styles are described later in this chapter.

Multiline JustificationMultiline justification determines how the line elements are offset from the defi

nition points provided. Definition points are the points you pick or coordinates youenter when drawing multilines. The justification is based on counterclockwise movement and can be specified only once during a single MLINE command sequence. TheJustification options are Top (default), Zero, and Bottom.

multiline: A singleobject consisting ofup to 16 parallel lineelements.

elements: The

individual lines that

make up a multiline.

spline: A specialtype of nonuniformcurved line.

definition points:The points you pickor coordinates youenter to specifymultilines.

497

498

To change the justification, type J at the first prompt displayed after entering theMLINE command. Enter the first letter of the desired justification format (T, Z, or B).The results of the three different Justification options using identical point entriesare shown in Figure 15-1. Observe each orientation as you go through the followingcommand sequence:

Command: ML or MLINEJ

Current settings: Justification = current, Scale = current, Style = currentSpecify start point or [Justification/Scale/STyle]: J JEnter justification type [Top/Zero/Bottom] <current>: (type T, Z, or B, and press [Enter])Current settings: Justification = specified value, Scale = current, Style = currentSpecify start point or [Justification/Scale/STyle]: 2,2JSpecify next point: 6,2JSpecify next point or [Undo]: 6,6JSpecify next point or [Close/Undo]: 2,6JSpecify next point or [Close/Undo]: CJCommand:

The current multiline justification setting is stored in the CMLJUST system variable.You can change the setting by entering 0 for the Top option, 1 for the Zero option, or 2for the Bottom option.

j

As shown in Figure 15-1, the multiline Justification options controlthe direction of the offsets for elements of the current style. The multiline segments in these examples are drawn in a counterclockwisedirection. Unexpected results can sometimes occur when you use theMLINE command, depending on the justification and drawing direction.

Exercise 15-1Complete the exercise on the Student CD.

Adjusting the Multiline ScaleThe Scale option of the MLINE command is a multiplier applied to the offset

distance specified in the multiline style. The multiplier is stored in the CMLSCALEsystem variable. The example in the previous section used a default scale setting of1. With this setting, the distance between multiline elements is equal to 1 times the

Figure 15-1.Multilines drawn using each of the three justification options. The definition points(represented by plus symbols) are picked in a counterclockwise rotation.

Top Justification Zero Justification Bottom Justification

AutoCAD and Its Applications—Basics

offset distance. For example, if the offset distance is .5, the distance between multilineelements is .5 when the multiline scale is 1. If the multiline scale is specified as 2,however, the distance between multiline elements is 1 (.5 x 2). Multilines drawn withdifferent scale settings are shown in Figure 15-2.

Exercise 15-2

C Complete the exercise on the Student CD.

Creating Multiline StylesMultiline styles are defined using the Multiline Style dialog box. The current style is

stored in the CMLSTYLEsystem variable. The Multiline Style dialog box can be accessed bypicking Format > Multiline Style... from the pull-down menu or by typing MLSTYLE.

The Multiline Style dialog box allows you to define, edit, and save multiline styles.See Figure 15-3. You can save styles to an external file so they can be used in otherdrawings. The Preview of: area in the lower part of the Multiline Style dialog boxdisplays a representation of the selected multiline style.

Figure 15-2.Multiline scale

settings.

Figure 15-3.The Multiline Styledialog box is usedto define, edit, andsave multiline styles.

Scale =.25

List of available

styles

Description ofselected style

Preview of

selected style

Chapter 15 Multilines and Splines

Scale = .5 Scale = 1

IMultiline Style

CurrentMultiline Style:STANDARD

Styles:

'mmniSTANDARD

Description:

Pieview of: R0AD1

Scale = 2

Set Current

New.. 3fModify.. Zf

Delete ^

Load.. iSave.

Help

Sets the

selected stylecurrent

Creates a

new style

Modifies the

'selected style

Renames the

selected style

„. Deletes theselected style

|\ Allows you toimport a style

from an

external file

\ Saves theselected style toan external file

499

Icaps: Short linesconnecting thestart points andendpoints ofmultiline elements.

500

Picking the New... button in the Multiline Style dialog box displays the Create NewMultiline Style dialog box shown in Figure 15-4.In the New Style Name: text box,entera name for the new multiline style. The properties from an existing style can be usedfor the new style by selecting it from the Start With: drop-down list.

After a name has been entered, the Continue button becomes active. Picking thisbutton opens the New Multiline Style dialog box. The options in this dialog box definethe appearance of the multiline. See Figure 15-5.The Description: field is optional, butit can be used to enter a brief description of the multiline style.

Using the caps, fill, and joints settings

The settings in the Caps area control the placement of caps on multilines. Capsare lines connecting the corresponding vertices of the start points or endpoints of themultiline elements. Using the checkboxes, you can set caps at the start points, endpoints,or both. Several examplesof differentcap options are shown in Figure 15-6.

Figure 15-4.Tocreate a new multiline style, specify a name and existing multiline style settings in theCreate New Multiline Style dialog box.

ICreate New Multiline StyleType in a name

for the new style

Select an existing|\ style to use its

properties forthe new style

New Style Name:

Stait With R0AD1

Cancel Help

Figure 15-5.The options in the New Multiline Style dialog box control all the settings for a multiline.

Caps areacontrols

multiline""capping

Determines the

fill setting forthe multiline""

style

Option for —displaying joints

SJNew Multiline Style: WALLS

Description:

Caps

Line:

Outer arc:

Inner arcs:

Start

•

•

•

End

•

•

•Angle: 90.00 130.00

Fill color: 'fj None V

.Display joints: fj

Figure 15-6.Various cap options used with multilines.

Caps Off Line Caps On

Description ofthe style

Offset Color Linetype

10.5 BYLAYER ByLayer 1•0.5 BYLAYER ByLayer

Add

Offset:

Color:

Linetype:

Delete

,0.500

| ByLayer

Linetype..

Outer Arcs On

v

Help

Elements area

sets the lines

and their

properties

Inner Arcs On

90° AngleCaps Off

45° AngleCaps Off

45° AngleLine Caps On


The caps can be drawn as straight lines or arcs.Arcscan be set to connect the ends ofthe outermost elements only,pairs of inner elements, or both the outer and inner elements.The multiline style must contain at least two multiline elements for outer arcs to be drawn.Arcs are drawn tangent to the elements they connect. You can also change the angle of thecaps relative to the direction of the multiline elements.Todo this, enter values in the Angle:text boxes. There is a text box for the start points and another for the endpoints.

The Fill color: setting in the Fill area allows you to create a solid multiline. Whenthe Fill color: setting is set to None, there is no fill. To specify the fill color, select a colorfrom the Fill color: drop-down list. Multilines drawn with and without fills are shownin Figure 15-7.

When Display joints: is checked, joints are displayed on the multiline. Joints arelines connecting the vertices of adjacent multiline elements. They are also referred toas miters. Multilines drawn with and without joints are shown in Figure 15-8.

Setting the element propertiesThe Elements area allows you to add or delete more elements (lines) from the

multiline style and specify the properties of each element. The options in this areachange properties including linetype, color, and offset. After you have set the properties, pick OK to apply them to the new multiline style. The new style is then added tothe Multiline Style dialog box.

Changing the Multiline StyleYou can specify the current multiline style by using the STyle option of the MLINE

command. To use a saved multiline style, enter ST to access the STyle option, and thenenter the style name. Before you can access a new multiline style, however, you mustcreate and save it using the Multiline Style dialog box.

If you forget the name of the desired multiline style, you can enter ? at the Entermline style name or [?]: prompt. The text window opens, listing the currently loadedmultiline styles. See Figure 15-9. Type the name of the style you want to use.

If you try to specify a multiline style that is not loaded, the Load multiline style fromfile dialogbox is displayed. You can look for the desired multiline style in the acad.min filelibrary,or you can pick the Tools button and then Find... to open the Find: dialog box.

Exercise 15-3

C Complete the exercise on the Student CD.

Figure 15-7.The multiline

Fill color: settingallows you to drawmultilines with a

solid fill pattern.

Figure 15-8.Multilines can be

drawn with or

without displayedjoints.


FillSetting On FillSetting Off

Joints Enabled Joints Disabled

joints (miters):Lines connectingthe vertices ofadjacent multilineelements.

501

background: Thefirst multiline youselect to create

a closed cross

intersection.

foreground: Thesecond multiline

you select to createa closed cross

intersection.

502

Figure 15-9.A list of loaded

multiline styles canbe displayed in thetext window.

c

n AutoCAD Text Window • Drawing5.dwg

Edit

Command: HL

HLINE

Current settings: Justification = Top, Scale - 1.00, Style = P.OAD1

Specify start point or [Justification/Scale/STyle]: ST

Enter mline style name or [?]: ?

Loaded mline styles:

Name Description

R0AD1 TU0-LANE ROAD UITH CENTERLINE

STANDARD

Enter mline style name or [?]: |

Editing Multilines

•

)The MLEDIT command permits limited editing operations for multiline objects.

Todisplay the Multilines Edit Tools dialog box, pick Modify >Object > Multiline... fromthe pull-down menu or type MLEDIT. See Figure 15-10. This dialog box contains fourcolumns. Each column contains three buttons of related command options. The imageon each button gives you an example of what to expect when using the editing option.

When you pick a button, the dialog boxclosesand AutoCAD prompts you to continuewith the command. The command options are described in the following sections.

Editing IntersectionsThe first (left) column in the Multilines Edit Tools dialog box displays three

different types of multiline intersections. Picking a button allows you to create thetype of intersection shown. The effects of the buttons in the first column are shown inFigure 15-11 and described below.

• Closed Cross. When you use this option, the first multiline you select is calledthe background, and the second multiline is called the foreground. A closedcross intersection is created by trimming the background, while the foregroundremains unchanged. The trimming is apparent, not actual. The line visibility ofthe background multiline is changed, but it is still a single multiline.

Figure 15-10.The Multilines Edit

Tools dialog boxhas twelve different

options for editingmultilines. Cross _

options

'Multilines Edit Tools

To use a tool, click on the icon. Objecl selection must be performed afterthe tool has been selected

MO r,.,-.EctTec::

Closed Doss

•JZJOpen Cross

bidMerged Cross

Closed Tee Coiner Joint

~\r

Open Tee

nPMerged Tee Delete Vertex

Cutting andweldingoptions

Corner jointand vertex

options


Figure 15-11.Creating closedcross, open cross,and merged crossintersections

with the MLEDIT

command.

[Original CrossingMultilines

Closed Cross Open Cross Merged Cross

First

pick^^[ ]

+

/Second pick J

Open Cross. Select the Open Cross button to trim all the elements of the firstmultiline and only the outer elements of the second multiline. The commandsequence is the same as that used for the Closed Cross option.Merged Cross. The Merged Cross button allows you to trim the outer elementsof both multilines. The inner elements are not changed.


Editing TeesThe buttons in the second column of the Multilines Edit Tools dialog box are used to

edit multiline tees. The results of using the tee options are illustrated in Figure 15-12.Thethree options are:

• Closed Tee. Trims or extends the first selected multiline to its intersection with

the second multiline.

• Open Tee. Trims the elements where a trimmed or extended multiline intersectswith another multiline. The first pick specifies the multiline to trim or extend,and the second pick specifies the intersecting multiline. The intersecting multiline is trimmed and left open where the two multilines join.

• Merged Tee. Trims the intersecting multiline after the first multiline is trimmedor extended. The inner elements, however, are joined. This creates an openappearance with the outer elements, while merging the inner elements.

Figure 15-12.Using the teeoptions of theMLEDIT command to

edit multiline tees.

[ OriginalMultilines

Closed Tee Open Tee Merged Tee

First pick

rh>^or JIL

\^_Second pick

J

Chapter 15 Multilines and Splines 503

504


Editing Corner Joints and Multiline VerticesThe buttons in the third column of the Multilines Edit Tools dialog box provide

options for creating corner joints and editing multiline vertices. The three options are:• Corner Joint. Creates a corner joint between two multilines. The first multiline

is trimmed or extended to its intersection with the second multiline, as shownin Figure 15-13.

• Add Vertex. Adds a vertex to an existing multiline at the location you pick.See Figure 15-14. The command sequence differs slightly from the sequencesused with the other MLEDIT options. After you select the Add Vertex option,AutoCAD prompts you to pick a location for the vertex.

• Delete Vertex. Removes a vertex from an existing multiline. The vertex closestto the location you pick is deleted. See Figure 15-14. The command sequence isthe same as for the Add Vertex option.


Figure 15-13.A corner joint can be created between two multilines using the Corner Joint option of theMLEDIT command.

CrossingMultilines

Pick the second multiline

Pick the first multiline

Multilines after Usingthe Corner Joint Option

Figure 15-14.The Add Vertexand Delete Vertex options of the MLEDIT command are used to edit multiline vertices.

Vertex is added Vertex closest to pickat picklocation location is deleted

Multiline before

Vertex Is Added

Multiline after

Vertex Is Added

Multiline before

Vertex Is Deleted

Multiline after

Vertex Is Deleted


Figure 15-15.The MLEDIT cuttingoptions allow you tocut single multilineelements or entiremultilines between

two specified points.

f OriginalMultiline

Cut Single Cut All ^\

Pick

points

—Q E3—

)V

Cutting and Welding MultilinesThe fourth column of buttons in the Multilines Edit Tools dialog box is used for

cutting a portion out of a single multiline element or the entire multiline. The spacesbetweenmultilineelementscan also be connected. AutoCAD refers to the connectingoperation as welding. The MLEDIT cutting and welding options are:

• Cut Single. Cuts a single multiline element between two specified points, asshown in Figure 15-15. Cutting affects only the visibility of elements and doesnot separate a multiline object. The multiline is still a single object. After youselect the Cut Single option, AutoCAD prompts you to pick the cutting points.

• Cut All. Cutsallelements ofa multiline between specified points. See Figure15-15.The multiline is still a single object, even though it appears to be separated.

• Weld All. Repairs all cuts in a multiline. Select the Weld All button and select apoint on each side of the cut multiline. The multiline is restored to its precutcondition.

cMultilineobjects can be converted to individual line segments withthe EXPLODE command. This command is explained in Chapters14 and 23.


c Drawing Splines

The SPLINE command is used to createa special type ofcurve called a nonuniformrational B-spline (NURBS) curve. A NURBS curve is considered to be a true spline.A spline created by fitting a spline curve to a polylineis merelya linear approximationof a true spline and is not as accurate. An additional advantageof spline objects oversmoothed polylines is that splines use less disk space. Toaccess the SPLINE command,pick the Spline button on the 2D Draw control panel of the Dashboard or the Drawtoolbar, pick Draw >Spline, or type SPL or SPLINE. A spline is created by specifyingthe control points using any standard coordinate entry method.


cutting: Theprocess deleting aportion of a multilineelement or an entire

multiline.

welding: Theprocess ofconnecting thespaces betweenmultiline elements.

nonuniform

rational B-spline(NURBS) curve: Atrue (mathematicallycorrect) spline.

limi

SPLINE

SPL

2D Draw

> Spline

H

Draw

Spline

Draw

> Spline

LU

Z

_1

Q.

CO

505

506

Command: SPL or SPLINEJ

Specify first point or [Object]: 2,2JSpecify next point: 4,4JSpecify next point or [Close/Fit tolerance] <start tangent>: 6,2JSpecify next point or [Close/Fit tolerance] <start tangentx JSpecify start tangent: JSpecify end tangent: JCommand:

After you have specified all the necessary points along the spline, press [Enter] toend the point specification process and to allow the start tangency and end tangencyto be entered. Specifying the tangents changes the direction in which the spline curvebegins and ends. Pressing [Enter] at these prompts accepts the default direction, ascalculated by AutoCAD, for the specified curve. The results of the previous commandsequence are shown in Figure 15-16.

If you specify only two points for a spline curve and accept AutoCAD's default start and end tangents, an object that looks like a lineis created, but the object is a spline.

Drawing Closed SplinesThe Close option of the SPLINE command enables you to draw closed splines. See

Figure 15-17. After closing a spline, you are prompted to specify a tangent directionfor the start point or endpoint of the spline. Pressing [Enter] accepts the default calculated by AutoCAD.

Figure 15-16.A spline drawnwith the SPLINE

command.

AutoCAD's default

start and end

tangents were usedfor this spline.

Figure 15-17.Using the Closeoption of the SPLINEcommand with

AutoCAD default

tangents to drawa closed spline.Compare this splineto the object shownin Figure 15-16.


Altering the Fit Tolerance SpecificationsWhen drawing splines, you can achieve different results by altering the speci

fications used with the Fit tolerance option. The outcomes of different settings varydepending on the configuration of the individual spline object. Thesetting specifies atolerance within which the spline curve falls as it passes through the controlpoints.

Specifying the Start and End TangentsThe previous SPLINE command examples used AutoCAD's default start and

end tangents. You can set start and end tangent directions by entering values at theprompts that appear after you pick the points of the spline. The tangency is based onthe tangent direction of the selected point. The results of using the horizontal andvertical tangent directions using Ortho mode are shown in Figure 15-18.

Converting a Spline-Fitted Polyline to a SplineA spline-fitted polyline objectcan be converted to a spline objectusing the Object

option of the SPLINE command.This option works forboth 2Dand 3Dpolylines.


Figure 15-18.These splines weredrawn through thesame points, butthey have differentstart and end

tangent directions.The arrows

indicate the tangentdirections.

C

Vertical Tangents

Editing Splines

Horizontal Tangents

3The SPLINEDIT command allows you toedit spline objects. Severalediting options

areavailable. You canadd,move, or deletecontrol pointstoalter theshape ofan existingcurve. You can also open or close a spline and change the start and end tangents.

To access the SPLINEDIT command, pick the Edit Spline button on the Modify IItoolbar, pick Modify >Object > Spline, or type SPEor SPLINEDIT. You are prompted toselect the spline to be edited. When you pick a spline, the control points are identified

fit points: Splinecontrol points.

by grips, as shown in Figure 15-19. You must then select one of the six SPLINEDIT EBB—Modify

> Object> Spline

options. These are described in the following sections.

Editing Fit DataThe Fit data option of the SPLINEDIT command allows spline control points to

be edited. Spline control points are called fit points. The Fit data option has severalsuboptions:


Open

Move vertex

Refine

rEverse

Undo

507

508

Figure 15-19.The control pointsfor a spline aredisplayed as grips.

•

Command: SPE or SPLINEDITJ

Select spline: (pick a spline)Enter an option [Fit data/Close/Move vertex/Refine/rEverse/Undo]: FJEnter a fit data option[Add/Close/Delete/Move/Purge/Tangents/toLerance/eXit] <eXit>:

Each of the Fit data suboptions is explained next. See Figure 15-20 for examples ofusing these options.

• Add. This suboption adds new fit points to a spline definition. A new fit pointcan be located by picking a point or entering coordinates. Fit points appear asunselected grips. When a fit point is selected, it becomes highlighted along withthe next fit point on the spline. You can then add a fit point between the twohighlighted points. If the endpoint of the spline is selected, only the endpoint

Figure 15-20.Examples of usingthe Fit data optionsof the SPLINEDIT

command to edit

a spline. Comparethe original splineto each of the edited

objects.Original Spline

Moving a Fit Point

Originallocation

New

location

Using the Close Option

D-

Adding aFit Point

Deleted

point

Deleting a Fit Point

Start and

end tangents

Editing the Tangents

-D


becomes highlighted. If the start point of the spline is selected, you are askedwhether you want the new fit point inserted before or after the existing one.Respond by entering Aor Baccordingly. When a fit point is added, the splinecurve is refit through the added point.

TheAdd suboptionfunctions ina runningmode. Thismeansyoucancontinueto add points as needed. By pressing [Enter] at a Specify new point <exit>: prompt,youcanselect otherexisting fit pointstoadd pointsanywhere on the spline.

• Close/Open. If the selected spline is open, the Close suboption is displayed. Ifthe spline is closed, the Open suboption is displayed. These options allow youto open a closed spline or close an open spline.

• Delete. The Delete suboption deletes fit points as needed. At least two fitpoints, however, must remain. Like the Add suboption, the Delete suboptionoperates in a running mode, allowing as many deletions as needed. The splineis recurved through the remaining fit points.

• Move. This suboption allows fit points to be moved as necessary. When youenter the Move suboption, the start point of the spline is highlighted. You canspecify a different location by pickinga new point. You can also specify otherfit points to move. The options are explained as follows:• Specify new location. Allows you to move the currently highlighted point to

a specified location.• Next. Highlights the next fit point. Thisoption is activated by pressing [Enter].• Previous. Highlights the previous fit point.• Select point. Allows you to pick a different fit point to move.• eXit. Returns you to the Fit data option prompt.

• Purge. This suboption lets you remove fit point data from a spline. After usingthis option, the resulting spline is not as easy to edit. In very large drawingsin which many complex splines have been created, such as GeographicalInformationSystems (GIS) drawings, purging fit point data reduces the file sizeby simplifying the spline definitions. Aftera spline is purged, the Fit data optionis no longerdisplayed by the SPLINEDIT command for the purged spline.

• Tangents. This suboption allows you to edit the start and end tangents for anopen spline and the start tangent for a closed spline. The tangency is based onthe direction of the selected point. You can also use the System default optionto set the tangency values to the AutoCAD defaults.

• toLerance. Fit tolerance values can be adjusted using this suboption. The resultsare immediate, so the fit tolerance can be adjusted as necessary to producedifferent results.

• eXit. Entering this suboption returns you to the SPLINEDIT command optionprompt.

Opening or Closing a SplineThe Openand Close options of the SPLINEDIT command are alternately displayed,

depending on the current status of the spline objectbeing edited. If the spline is open,the Close option is displayed. The Open option is displayed if the spline is closed.

Moving a VertexThe Move vertex option of the SPLINEDIT command allows you to move the fit pointsof a spline. When you access this option,you can specifya new location for a selectedfit point.The options displayed are identical to thoseused with the Move suboption ofthe Fit data option.You can picka new location forthe highlighted fit point, or you canenter a suboption. The Move vertex suboptions are explained below:

• Specify new location. Moves the currently highlighted point to a specified location.• Next. Highlights the next fit point.


Iorder: In a spline,the degree of thespline polynomial+ 1.

510

Previous. Highlights the previous fit point.Select point. Picks a different fit point to move, rather than cycling throughpoints with the Next or Previous suboptions.eXit. Returns to the SPLINEDIT prompt.

Exercise 15-9Completethe exercise on the Student CD.

Smoothing or Reshaping a Section of the SplineThe Refine option of the SPLINEDIT command allows fine-tuning of the spline

curve. Fitpointscanbe added to help smooth or reshape a section of the spline. Whenyouuse thisoption, thefit pointdataisremoved from thespline. Thefollowing refiningoptions are available:

• Add control point.Specifies new fit points on a spline as needed.• Elevate order. Causes more control points to appear on the curve for greater

control. The order ofa spline is the degree of the spline polynomial +1. In simpleterms, it is the degree of refinement of the spline. For example, a cubic splinehas an order of 4. In Figure 15-21, the order of the spline is elevated from 4 to 6.The order setting can be from 4 to 26, but it cannot be adjusted downward. Forexample, if the order is set to 24, the only remaining settings are 25 and 26.

• Weight. Changes the weight of a control point. When all control points havethe same weight, they exert the same amount of pull on the spline. When aweight value is reduced for a control point, the spline is not pulled as closeto the point as before. Likewise, when a weight value is increased, the controlpoint exerts more pull on the spline. See Figure 15-21. The default setting of1.0000 can be adjusted to a higher or lower value. The weight setting must bepositive. The control point selection suboptions of the Weight option are thesame as those used with the Move vertex option of the SPLINEDIT command.You can specify a new weight for the highlighted control point using the Enternew weight option.

Figure 15-21.The effects of

elevating theorder of a splineand increasingthe weight of anindividual control

point.

OriginalSpline

•

Control

point

Increasing the Weightof One Control Point

Elevating the Orderfrom 4 to 6

Increasing the weight ofthis control point to 6 pullsthe spline away from the

other control points


Reversing the Order of Spline Control PointsThe rEverse option of the SPLINEDIT command allows you to reverse the listed

order ofthespline control points. This makes theprevious startpointthenewendpointand the previous endpoint the new start point. Using this option affects the variouscontrol point selection options.

Undoing Splinedit ChangesThe Undo option of the SPLINEDIT command undoes the previous change made

to the spline. You can use this option to undo changes back to the beginning of thecurrent SPLINEDIT command sequence.


Chapter TestAnswer the following questions. Write your answers on a separate sheet ofpaperorcomplete the electronic chapter test on the Student CD.

1. Give the command and entries needed to draw a multilinewith zero justificationand the saved style ROAD1.A. Command:

B. Current settings: Justification = current, Scale = current, Style = currentSpecify start point or [Justification/Scale/STyle]:

C. Enter mline style name or [?]:D. Current settings: Justification = current, Scale = current, Style = ROAD1

Specify start point or [Justification/Scale/STyle]:E. Enter justification type [Top/Zero/Bottom] <current>:F. Current settings: Justification = Zero, Scale = current, Style = ROAD1

Specify start point or [Justification/Scale/STyle]:G. Specify next point:H. Specify next point or [Undo]:

2. Name the MLINE command option that establishes how the resulting lines areoffset based on the definition points provided.

3. Name the system variable that controls the multiplier value for the offset distances specified with the MLINE command.

4. How do you access the Multiline Style dialog box?5. Define caps.6. Define joints.7. What is displayed when you enter the MLEDIT command?8. How do you accessone of the MLEDIT options?9. List the three options used for editing multiline intersections with the MLEDIT

command.

10. Name the MLEDIT option in which the intersecting multiline is trimmed and leftopen after the first multiline is trimmed or extended to its intersection with theintersecting multiline.

11. Name the MLEDIT option that allows you to remove a vertex from an existingmultiline.

12. Name the MLEDIT option that lets you removea portion from an individual multiline element.

Cliapter 15 Multilines and Splines 511

512

13. Name the MLEDIT option that removes all the elements of a multiline betweentwo specified points.

14. Name the MLEDIT option that repairs allcutsin a multilinebetweentwoselectedpoints.

15. Name the command that can be used to create a true spline.16. How do you accept the AutoCAD defaults for the start and end tangents of a

spline?17. Name the SPLINE command option that allows you to turn a spline-fitted poly

line into a true spline.18. Name the command that allows you to edit splines.19. What is the purpose of the Addsuboptionof the Fit data option of the SPLINEDIT

command?

20. What is the minimum number of fit points for a spline?21. Name the SPLINEDIT option that allows you to move the fit points in a spline.22. What is the purpose of the Refine option of the SPLINEDIT command?23. Identify the Refine suboptionof the SPLINEDIT command that lets you increase,

but not decrease, the number of control points appearing on a spline curve.24. Name the Refine suboption of the SPLINEDIT command that controls the pull

exerted by a control point on a spline.25. How many operations can you undo inside the SPLINEDIT command with the

Undo option?

Drawing ProblemsStart a new drawing for each of the following problems. Specify your own units, limits, andother settings to suit each problem.

1. Draw the objects shown using the MLINE command. Usethe justification optionsindicated with each illustration. Set the limits to 11,8.5; grid spacing to .50; snapspacing to .25; and the offset for themultiline elements to .125. Donot add textordimensions. Save the drawing as P15-1.

2.50

1.50

Zero

JustificationBottom

Justification

2.50

1.50

TopJustification


2. Draw the partial floor plan using the multiline commands. Carefully observehow the dimensions correlate with the multiline elements to determine your justification settings. Also, use the appropriate cap and multiline editing options.Use architectural units. Set the limits to 88",68"; grid spacing to 24"; and snapspacing to 12". Make all walls 6" thick. Do not add dimensions. Save the drawingas P15-2.

48-0"

24-0" 24-0'

,^_L 3'-0"

3' S'-6'

4-0" 6'-0' 6'-0" 4'-0" 8'-0"

3. Draw the proposed subdivision map using the multiline commands. The roadsare 30' wide. Use a centerline linetype for the center of each road. Adjust the line-type scale as needed. Do not include dimensions. Save the drawing as P15-3.

Cliapter 15 Multilines and Splines 513

514

4. Draw the partial floor plan using multilines for the walls. Do not dimension thefloor plan. Save the drawing as P15-4.

5. Draw the proposed electrical circuit using the multiline commands. Establish aline offset proportional to the given layout. Use a phantom linetype for the centerof each run. Do not draw the grid, which is provided as a drawing aid. Save thedrawing as P15-5.


6. Use SPLINE and other commands, such as ELLIPSE, MIRROR, and OFFSET, todesign an architectural door knocker similar to the one shown. Use an appropriate text command and font to place your initials in the center. Save the drawingas P15-6.

7. Use the SPLINE command to draw the curve for the cam displacement diagrambelow. Use the following guidelines and the given drawing to complete thisproblem:A. The total rise equals 2.000.B. The total displacement can be any length.C. Divide the total displacement into 30° increments.D. Draw a half circle divided into 6 equal parts on one end.

Draw a horizontal line from each division of the half circle to the other end

of the diagram.Draw the displacement curve with the SPLINE command by picking pointswhere the horizontal and vertical lines cross.

G. Label the displacement increments along the horizontal scale as shown. Savethe drawing as P15-7.

E.

F.

T0TA

RISE

. C ISF'LACE MENT -

FALL

s J-

2.

4/ \

M DO

*v \1^— X

0* 60' 120* 180' 240' 300" 360"

30" 90" 150* 210" 270' 330'


n

516

l Draw a spline similar to the original spline shown below. Copy the spline seventimes to create a layout similar to the one given. Perform the SPLINEDIT operations identified under each of the seven copies. Save the drawing as P15-8.

Original Spline Close Move a Control Point Elevate the Order to 10

Add Two Control Points Delete a Control Point Edit the Tangents Increase the Weight ofa Control Point to 4


learning objectives - los rios community college...

Documents