AutoCAD R12 Tutorial 3


	FBE AutoCAD Page

Stephen Peter, S.Peter@unsw.edu.au

Introduction

In this tutorial you will draw a plan of Brunelleschi's Church of San Maria Degli Angeli (Florence, Italy, 1434-1436), from Clark and Pause's, "Precedents in Architecture", page 28; have a look at figure 13 at the end of the handout. You will note that the church has eight "bays" and that each bay is itself symmetrical. You will draw half of one bay and then mirror that half to create a whole bay and then copy that to complete the plan...

This tutorial introduces a number of AutoCAD construction commands:

offset,
array, and
mirror,

and a number of AutoCAD editing commands:

fillet,
trim,
break, and
extend.

In case all that isn't enough for you, you will also learn about "layers", hatching and grip editing.

Setting Limits and Units

You will draw the building in a 50x50m space, but this time, the limits will centre on 0,0!

    limits [return]
    -25000,-25000 [return]
    25000,25000 [return]

    units [return]
    [return]                 accept default = 2 = Decimal
    0 [return]               no decimal points

accept all the remaining defaults!

    rectang [return]
    -25000,-25000 [return]
    25000,25000 [return]

    z [space] a [space]      zoom all - to see the whole drawing.

Layers

Most CAD systems have some kind of overlay concept. AutoCAD uses layers. Layers are used to separate and structure drawings; layers can be turned on and off (for example to vary the amount of detail in a drawing), and can have linetypes associated with them....

When you draw in AutoCAD the graphics appears on the current layer, so once you start using layers, you need to be careful that the current layer is correct. Look near the top-left of the screen: the current layer and it's colour is listed there.

select:

    /Settings . Layer Control/

type:

    const

click on "New",
click on layer "CONST" in the list of layers,
click on "Set Color",
select a colour by clicking on it,
click on "OK" to dismiss the set-color dialog box,
click on Current to make this the drawing layer, and finally,
click on OK to dismiss the layer-control dialog box.

Draw "Construction" Lines

Draw a line from the centre of the building:

    line [return]            LINE command
    0,0 [return]
    0,-17500 [return]
    @3000,0 [return]
    [return]                 end the command.

Before continuing, you should "zoom in" to the lines, type:

    z [space] w [space]

enclose the lines in the selection rectangle, leave a fair amount of space to the left and right of the lines.

If the lines are near the left of the screen and being obscured by the axis display, type:

    p [return]               pan the view!

pick a position in the middle of the lines;
pick another position in the middle of the screen.

Select

    /Construct . Offset/
    250 [return]

select the short horizontal line;
pick a point anywhere above the line;
select the new line
pick a point anywhere above it.

    [return]                 end the command

This should produce one vertical and three horizontal lines.

Now use array to copy lines, select:

    /Construct . Array/
    w [return]               to specify a selection window

enclose the lines just drawn in the selection rectangle

    [return]                 end the selection process
    p [return]               polar "array"
    0,0 [return]             the centre of the rotation
    2 [return]               items (originals plus the copy)
    22.5                     angle
    y [return]               need to rotate objects!

This same technique could have been used in last week's tutorial, except that I wanted to introduce "blocks".

The lines at the bottom represent the outside of the building. Connect these lines by typing:

    fillet [return]

select the right-hand end of the bottom horizontal line;
select the outer of the three sloping lines

Fillet will extend the two lines until they connect to each other.

Figure 1 Points to be selected for the Trim

Now you will trim the sloping line back to the line from the, select:

    /Modify . Trim/

select the right-hand line coming from the centre (see figure 1);

    [return]                 end the selection process

select the line to be trimmed;

    [return]                 to end the command.

Repeat the fillet and trim process for the two inner lines!

Draw the Floor Pattern

Before you draw the floor pattern, you'll create a new layer (without using the dialogue box), type:

    layer [return]
    new [return]             choose to create a new layer
    floor [return]           name the new layer
    set [return]             set the current layer
    floor [return]           make the new layer the current layer.
    [return]                 end the command.

Now we will start to draw the horizontal lines of the floor pattern, type:

    line [return]            LINE command, can also use L [return].
    0,-6500 [return]
    @5000,0 [return]         we will trim this line later.
    [return]                 end the command.

Select:

    /Construct . Offset/
    625 [return]             offset distance.

select the line just drawn;
click below the line to indicate the direction of offset.

    [return]                 end the command.

    [return]                 start another offset
    1375 [return]            offset distance

select the last line created by the offset;
click below the line to offset down.

    [return]                 end the command.

Offset this line 625 down.

If that worked, you should have two pairs of lines. These lines will form the pentagon patterns in the centre of the building.

Continue offsetting the "last" line, using the following offsets: 500, 750, 500, 4625, 500. That's most of the horizontal lines in the plan.

Next, you will now draw the rest of the floor pattern. Have a look at figure 9 which shows the completed bay.

Firstly, offset the vertical (centre) line 2000 to the right, and then type:

    trim [return]

select the vertical line just created;

    [return]                 end the selection process.
    f [return]               choose to pick the lines via a "fence" line!

draw a fence line like that shown in figure 2.

    [return]                 end the fence line
    [return]                 end the command.

Figure 2 Trim "fence" line

    e [return]               erase!

select the vertical line used as the "trim guide".

    [return]                 end the command.


    r [return]               redraw the drawing - clean up the "blips".

    qsave [return]           save the drawing.
    tut3 [return]            enter a drawing name if prompted.

Now you will draw the line and arc floor pattern, select:

    /Draw . Line/            or type: line [return]
    end [return]             endpoint snap mode

select the right edge of the "bottom" trimmed line.

    end [return]             endpoint snap mode

select the right edge of the line above it.

    [return]                 end the command.

Select:

    /Draw . Arc . Cen,Start,End/

select the midpoint snap mode;
select the middle of the line just drawn; type:

    @0,-1800 [return]
    @0,3600 [return]

That should have drawn an arc to the right of the line.

Now you will use "break" to remove the part of the line between the arc's endpoints. Break is an extremely useful command, that is used often in editing operations. Select:

    /Modify . Break . Select Object, Two Points/

select the vertical line that you drew a minute ago, then using the endpoint snap mode, select the bottom end of the arc, and finally using the endpoint snap mode again, select the top end of the arc.

Now draw a line joining the two other trimmed lines. HINT: use the endpoint snap mode!

Trim the four horizontal lines towards the centre of the bay, back to the right-hand edge of the "bay".

Figure 3 Zoom Window

The last floor pattern is at the top of the "bay". You will need to enlarge the view of the centre to be able to see it clearly. Type:

    z [space] w [space]

enter the selection window shown in figure 3

    line [return]            LINE command
    0,-600 [return]
    @1000,0 [return]

select the endpoint snap mode and pick the right-hand end of the top horizontal line below.

    [return]                 end the command.

Now you will use a new technique in AutoCAD called "grip-editing".

Click on the two lines just drawn, they should turn purple;
Click on the intersection point of the lines; type:

    int [return]             intersection snap mode.

click on the position where the horizontal line crosses the right-hand edge line. AutoCAD should move the selected vertex to the intersection point!

Zoom Dynamic

One of the most powerful of the zoom options is zoom-dynamic, it allows for zooming and panning at the same time. Type:

    z [space] d [space]

AutoCAD should draw the whole drawing, a purple rectangle showing the current view and the cursor will turn into a rectangle with a X cross at the centre. If you click with the left mouse button you can resize the zoom window's size (click again to fix the new size).

Move the zoom window (the cursor!) over the lower half of the "bay" and press [return]. If the arc has turned into a series of straight lines then type: regen [return] to re-generate the view.

Draw the Walls

Before drawing the walls, create a new layer called "walls", and set the layers colour to be something other than white, and make it the current layer .

Figure 4 Change properties selections

The wall is 700 outside the arc floor pattern, so we will offset that pattern. Offset the arc and the vertical lines on either end (to the right) by 700. Notice that the new lines are in the floor layer, you will need to change the lines into the walls layer. Type:

    chprop [return]          change properties.
    c [return]               specify a "crossing" selection rectangle

enclose the arc and the lines below it in the rectangle (see figure 4);
then select the line that was offset from the line at the top of the arc.

    [return]                 end the selection process.
    la [return]              selects "change layer"
    walls [return]           the new layer.
    [return]                 end the command.

Figure 5 Fillet points

Now you will join up the sections of the wall line outside the arc. Type:

    fillet [return]

select the bottom of the short vertical line and then select the horizontal line to the left of the vertical line (see figure 5).

    [return]                 restart the fillet command.

select the two points shown in figure 6.

Figure 6 Second Fillet points

That completes the bottom end of the bay.


    p [return]               pan the view.

pick a point near the top of the AutoCAD window, and then
pick a point about three-quarters of the way down the screen.

Select:

    /Construct . Offset/
    250 [return]

pick the bottom of the four lines that extend to the right edge-line;
pick a position below the line to indicate the offset direction.

    [return]                 end the command.

Figure 7 Third Fillet points

Now you will use fillet to clean up the rest of the wall lines: Type:

    fillet [return]

pick the short vertical line (see figure 7), and then
pick the right-hand end of the line just created.

    [return]                 to restart the fillet command.

pick the outer arc to the right of the vertical; pick the vertical above the arc.

Change the horizontal line into the walls layer (use the "chprop" command).

Lastly, you will extend the horizontal line to the right edge-line. Type:

    extend [return]

pick the right edge-line;

    [return]                 end the selection process.

pick to the right of the middle on the horizontal line.

    [return]                 end the command.

Draw the Passage Between the Bays

    z [space] p [space]      zoom to the "previous" view.

To draw the passage way we will firstly draw it's centre line, and then use offset to get the walls.

    line [return]            start the line command.
    cen [return]             to select the center snap mode

pick one of the arcs

    @3000,0 [return]         to show the direction of the line.
    [return]                 end the command.

    offset [return]
    500 [return]

pick the centre-line;
pick below the line;
pick the centre-line again;
pick above the line

    [return]                 end the command.

Extend the bottom line to the right edge-line (use "extend").

    line [return]            draw a line!

select the "intersection" snap mode;
pick the intersection of the outer arc and the top-most of the 3 lines;
select the "perpendicular" snap mode;
pick the right edge-line.

Erase the top two lines, and trim the bottom line back to the outer arc.

Finally, use /Modify . Break . Select Object, Two Points/ to remove the section of arc between the walls of the passage. Type r [return] to redraw the view.

Before mirroring the bay, you will hatch the wall areas! Firstly, turn off the "const" layer. Select:

    /Settings . Layer Control/

select "CONST", then "OFF" and then "OK".

AutoCAD should redraw the drawing without the specified layer!

Next you will draw lines to close off the wall sections, but before doing that, because we want all the lines to snap to the endpoints of existing lines we will tell AutoCAD to automatically use the endpoint snap mode! Type:

    osnap [return]
    end [return]

Now draw those lines, you may need to use zoom or pan to get all the lines in the view, see figure 8.

Figure 8 Third Fillet points

Once you've drawn the lines, turn the auto-snapping off by typing:

    osnap [return]
    off [return]

Hatching

The last thing to do is to hatch the wall areas! Before hatching it's often a good idea to save your drawing (use qsave)!

Create a new layer, called hatch, and make it current, and then select:

    /Draw . Hatch.../

pick "Hatch Options..."
pick "Pattern..."
pick "Next"
pick "AR-SAND"
enter a scale of 50
pick "OK"
pick "Select Objects"
select the lines that make up the two closed walls.

    [return]                 end the selection process.

pick "Apply".

AutoCAD should draw lots of dots, almost filling-in the wall area. If you have trouble call the tutor!

Finally, you need to erase the three lines you added to close the wall areas so you could hatch them (see figure 8). Use /Settings . Layer Control/ to turn the "hatch" layer OFF first. If you accidentally pick the wrong thing, type: r [return] to remove selections, and then a [return] to restart adding selections.

Once you've erased the three lines, turn the "hatch" layer back ON.

That completes the basic half bay!

Use zoom dynamic to view the whole of the bay. Then type:

    qsave [return]           save the drawing.

Figure 9 Completed Bay

Mirror the Half Bay

Now to mirror the section completed, select:

    /Construct . Mirror/
    w [return]

enclose all the graphics inside the selection rectangle.

    [return]                 end the selection process.

    0,0 [return]             the centre of the building will be the
                             start of the mirror line.

    @0,-1000 [return]        this creates a vertical line as the
                             mirror line, this causes the graphics
                             to be mirrored to the left.

    n [return]               don't delete the old objects.

Duplicate the Bay

Before continuing, do a zoom-all, so you can see the whole drawing. Then type:

    array [return]
    w [return]

select the whole bay.

    [return]                 end the selection process
    p [return]               select a polar array
    0,0 [return]             the centre of the building
    8 [return]               we want 8 bays!
    360 [return]             go all the way.
    y [return]               rotate as you go.

AutoCAD should copy the single bay through 360 degrees, giving 8 bays!

Save the drawing!

Last Gasps....

That's basically it, except for the doors! There are a few other details (such as a spiral stair) that we won't draw, but we will draw the entry.

Zoom in on the "eastern" bay (see figure 10), then erase the 4 hatching objects! Then redraw the screen.

Figure 10 Zoom in to locate Entry

You will now draw the centreline of the doorway, type:

    line [return]            start the line command

select the endpoint snap mode and pick the middle of the inner vertical wall line and then select the "perpendicular" snap mode end pick the outer vertical line (the line to the right of the one just picked).

Next offset the line 1250 "up" and "down" to make a 2500 wide doorway; and erase the centre-line.

Then you will use "trim" to take the inner two lines back to the doorway line. This is done because we want to hatch the wall area again, so can't have any lines "sticking out". Type:

    trim [return]

pick the (horizontal) doorway lines;

    [return]                 end the selection process.

pick the vertical lines (see figure 11).

Figure 11 Zoom in to locate Entry

Now draw the lines back(!), but as two lines, instead of the four. We could draw the door, but let's not bother!

Use zoom dynamic, to zoom out until you can see all the lines that make up the boundary of the area we now want to hatch. Draw lines (using the endpoint snap mode) to close off the two hatch sections (figure 12 shows one pair of line ends).

Figure 12 Lines to join

Before re-hatching, turn the HATCH layer OFF. Then hatch the four areas! You might find it easier if you zoom in on the top two areas, hatch them, then zoom in on the bottom two areas and hatch them. If you miss any of the wall edges the hatching will "leak out", if this happens, type: u [return] to undo the command and then hatch it again!

When you've done the hatching, use "chprop" to change the hatching to the HATCH layer and then turn the HATCH layer back ON.

Figure 13 Completed drawing

The entry has number of stairs (and some other details) and there is another entry on the opposite side but we'll leave that off!

    z [space] a [space]      zoom out to see the whole drawing (see
                             figure 13).

    end [return]             save the drawing!

FBE AutoCAD Page

2D-R12 Tutorial 4


Last Update : 8 April 2000 Major Revision : 29 October 1997 SEARCH . FBE SITEMAP		Disclaimer . Webmasters Page Contact : Stephen Peter Email : s.peter@unsw.edu.au