AUTOCAD MANIPULATION

Introduction
This church has been selected because it is very symmetrical. Whenever you are drawing anything, look carefully for symmetry and repetition, because CAD systems excel at those things.	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 20 at the end of the tutorial. 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...
Please note that the dimensions used in this tutorial are neither accurate nor correct! I don't have access to an accurately dimensioned drawing of the building so I've guessed the dimensions...	This tutorial introduces a number of AutoCAD construction commands: offset, 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! If these seem like particularly perverse drawing limits, it's because they ARE! I'm making sure that you are aware that the limits do not need to start at 0,0. Type:
The coordinates used make the centre of the drawing 0,0 which makes it easy to copy the church "bay" around.	limits -25000,-25000 25000,25000
	Like in the previous tutorial, we need to get rid of the 4 decimal points: select Format - Units, AutoCAD will display the "Drawing Units" dialog. Make sure Decimal is selected in the Units section and Decimal Degrees in the Angles section, then in Unit's Precision, click on the down arrow beside "0.0000" and select "0", and finally select "OK". Alternatively, type UNITS and then follow the prompts.
Zoom All	To reset the drawing view to the whole of the drawing, select zoom-all from the standard toolbar (or type: Z [space] A [space])
Don't forget to do this . . .	Now that you've "zoomed out", draw a rectangle using the coordinates from the drawing limits (this will provide a border for the drawing)!
	If the Axis label (which is called the "UCS icon") is distracting - I certainly find it so - you can hide it by selecting View - Display - UCS Icon - On.
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....
	Figure 1 The Layer status area (Object Properties toolbar).
	When using AutoCAD, the graphics appears on the current layer, so be careful that the current layer is correct. Look near the top-left of the screen: the current layer and it's colour is displayed there (see figure 1).
Layers icon The current layer is the layer to which new graphics is added. The properties command (which was introduced in the previous tutorial) cann be used to change a graphics object's layer (or linetype or colour).	Select the Layers icon or select Format - Layers..., AutoCAD will display the "Layer Properties Manager" dialog. Click on the "New" button and then type CONST (to change the default "layer1" name to something more meaningful), then click on the "Current" button to make this the current layer.
	Change the colour and then "OK" the dialog box.

Draw "Construction" Lines
Line icon	Draw a line from the centre of the building: select then line icon (or type L), and then type:
	0,0 0,-17500 @3000,0 terminate the command
Zoom Window	Before continuing, you should "zoom in" to the lines, select zoom-window (or type Z W), enclose the lines in the selection rectangle.
Offset	Select offset from the Modify toolbar (or type [the letter 'o'] O), and then type:
The offset command makes it easy to set up a series of grid line or (drawing) construction lines.	250 the offset distance select the short horizontal line pick a spot anywhere above the line select the new line pick a spot anywhere above it terminate the command
	This should produce one vertical and three horizontal lines.
Revisiting Polar Array
	Now you will use polar array to copy and rotate some lines.
Array (under the offset icon)	Select array from the modify toolbar (or type AR), then select the lines just drawn by picking a spot below and to the right of the "corner" and then another spot above and to the left or the "corner" - make sure the selection rectangle crosses the three horizontal lines (and the vertical line). Press to end the selection process, type P (to specify a polar array), type 0,0 (for the centre of the rotation), 2 (number of items), 22.5 (angle), Y (rotate the objects). Figure 2 The lines after using Array.
Editing
Fillet icon (be careful because it looks like chamfer). The Fillet command is exceptionally useful. It basically extends two lines until they meet, and optionally, inserts a curve where the lines join.	The lines at the bottom represent the outside of the building. To connect these lines select the fillet icon (or type F), look at the command line area - if the current fillet radius is NOT 0 (zero) - then type R 0 (that's a zero).
	If you had to change the radius, press type to restart the command. Select the outer of the three sloping lines, and then select the bottom horizontal line. AutoCAD will extend the two lines until they connect to each other. Figure 3 Fillet.
	Next, you will trim the sloping line back to the line from the centre.
	The trim command is another command that you use very often. The first point you specify selects the "cutting edge", that is, the line to which you are trimming back to. While succeeding selections identify lines to be trimmed.
Trim icon When picking lines to be trimmed, the part of the line that you select is important. In the example in figure 3, if you pick to the left of the first line selected (rather than to the right of it), then the line will be trimmed from the fillet point to the boundary line. In other words, you'll undo the fillet you just did!	Select the trim icon from the Modify toolbar (or type TR), for the "cutting edge" select a spot near "first point" on Figure 4, press (to end the selection process), select the line to be trimmed ("second point"); and press (to end the command). Figure 4 Points to be selected for the Trim
	Repeat the fillet and trim process for the other two inner lines!

Draw the Floor Pattern
Layers	Before you draw the floor pattern, you'll create a new layer, select the layers icon (or type LA ), create a new layer called FLOOR, and make it the current layer.
This line uses absolute & relative coords. (Figure 6 shows the finished floor pattern.)	To draw the horizontal lines of the floor pattern, select line (or type L ), and type 0,-6500 @5000,0 and press again (to end the command). This line will be trimmed later....
Offset icon	Select offset (or type OFFSET or just o ), type 625 (the offset distance), select the line just drawn, click below the line to indicate the direction of offset, and press again. Press (to start another offset), type 1375 (offset distance), select the last line created by the offset, click below the line to offset down, and press again to end the command.
Remember that you can restart the last command by pressing This is basically trying to teach you to watch (and interract with) the prompts that AutoCAD displays in the command area.	Offset this line 625 down! If that worked, you should have two pairs of lines. These lines will form the octagonal pattern 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 16 which shows the completed bay.
Trim icon I'm introducing the "fence" option because it makes it very easy to trim a whole series of lines by simply drawing a line that crosses them. The fence line works like the "crossing window" selection in that the objects that the line crosses are selected.	Firstly, offset the vertical (centre) line 2000 to the right, and then select : trim (or type TR ), pick the vertical line just created press (end the selection process), type F (this tells AutoCAD that you will draw a fence line - see figure 5), draw a fence line like that shown in the figure (it must cross the four lines shown), after you pick the second point of the fence line, press twice (firstly to end the fence line and secondly to end the command)! Figure 5 Trim fence line.
Alternatively, display the Object Snap Toolbar. Select View - Toolbars... check Object Snap (the toolbar will be displayed) and then click on close.	The following section uses a number of snap modes. The easiest way to work with snaps is to pre-set them and then let AutoCAD dynamically show which snap it can use...
	Right-click on "OSNAP" (in the status area at the bottom of AutoCAD's window) and select "Settings...", then turn "Endpoint" and "Midpoint" ON (by clicking on them). It would probably be a good idea to turn OFF any of the other snaps that are ON. Finally, make sure the "OSNAP" button is IN.
Erase icon Save icon	Select erase from the Modify toolbar (or type E ), select the vertical line used as the "trim guide", press (end the command). Now is a good time to save the drawing, select save (or press Ctrl-S), enter a drawing name if prompted (and don't forget to change the drive & directory if necessary).
Line icon Endpoint snap mode icon	Now you will draw the line and arc for the floor pattern, select line (or type L ) then, using the Endpoint snap mode (which should automatically be set by moving the cross-hair near the endpoint), select the right edge of the "bottom" trimmed line and (again using the Endpoint snap mode) select the right edge of the line above it, then press (end the command).
Midpoint snap mode icon The arc should start and end just "inside" the ends of the vertical line.	Select Draw - Arc - Center-Start-End (do NOT pick the arc icon) then, using the Midpoint snap mode select the middle of the line just drawn, then type @0,-1800 @0,3600. That should have drawn an arc to the right of the vertical line.
Break icon Break is an extremely useful command that is used often in editing operations. An alternative way to choose a snap mode is to hold the Ctrl key and click the right mouse button(!) - AutoCAD will display a pop-up menu with the snap modes. While we're talking about the mouse ;-), right-clicking in AutoCAD generally causes a context sensitive popup menu to be displayed (showing a selection of the options available "at the moment").	Now you will use "break" to remove the part of the line between the arc's endpoints. Select break (or type BR ), select the vertical line, type F (to specify that the next point will be the "first" point of the break), 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. Figure 6 Lines trimmed and broken! Now draw a line (using the Endpoint snap) joining the two other trimmed lines (see figure 6). Then trim the remaining four horizontal lines towards the top of the bay, back to the right-hand edge.
Zoom Window icon	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. Select zoom-window (or type Z W ), enter the selection window (so you can see at least the area shown in Firgure 7).
Polyine icon Intersect snap mode icon	Select polyline (or type PL), and then type 0,-600 @1000,0), then using the Endpoint snap mode, pick the right-hand end of the top horizontal line below, finally press to end the command. Figure 7 Grip editing positions. Now you will use a technique in AutoCAD called "grip-editing". Click on the lines just drawn (they'll become "dashed"), then click on the "joint" point of the lines ("First Pick" in Figure 7), select then Intersect snap mode, click on the position where the horizontal line crosses the bay's right-hand edge line ("Second Pick" in Figure 7). AutoCAD should move the selected vertex to the intersection point! Press the Escape key (ESC) twice to de-select the lines.
Zoom Dynamic
If you don't like the dynamic zoom command, there's always the scroll bars...	One of the most powerful of the zoom options is zoom-dynamic, it allows for zooming and panning at the same time. Type Z D or select the command from the zoom flyout (flydown?) shown in figure 8. Figure 8 Zoom Dynamic AutoCAD should draw the whole drawing, a green (or 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).
"REGEN" can be abbreviated to "RE"...	Move the zoom window (the cursor!) over the lower half of the "bay" and press . If the arc has turned into a series of straight lines then type REGEN to re-generate the view.
Draw the Walls
	Before drawing the walls, create a new layer called "WALLS", and set the layer's colour to be something other than white, and make it the current layer.
Don't forget to offset the line at the "top" of the arc (see figure 9)	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. Figure 9 Change properties selections. Select the lines and arc just created as well as the lines at the bottom (see figure 9) - do this by click first at about the bottom-right of the selection rectangle in figure 9 and then the top-left point.
	This should select everything except the line at the top, pick it now. Having selected the objects, now they'll be changed to the new layer. Go to the layers drop-down list and select "WALLS" (the layer you just created). All the selected objects will change to that layer! Press "Esc" (escape) twice to de-select the objects.
Fillet icon In selecting both these points, it's important where you click on the line! The first point should be in the bottom-half of the line, while the second point should be to the left of the (projected) first line.	Now you will join up the sections of the wall line. Select fillet (or type F), select the bottom of the short vertical line and then select the horizontal line to the left of the vertical line (see figure 10). Figure 10 Fillet points.
	Now, use fillet on the lines shown in figure 11. Note that the extact position that you pick is not important, but, it is important that you pick to the right (1st point) and below (2nd point) the intersection, the part you pick (at this stage of the fillet command) is the part that AutoCAD will not remove! Figure 11 Second Fillet.
Save icon	That completes the bottom end of the bay. Have you saved your drawing recently?
	Now use the scroll bars to move the view so that you can see more of the lines at the "top" - you need to be able to see the top of the arc you drew earlier (see figure 12).
Offset icon	Select offset (or type o [the letter 'o']), and then type 250, 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, press to end then command.
Fillet icon	Now you will use fillet to clean up the rest of the wall lines. Select fillet (or type F ), pick the short vertical line (see figure 12), and then pick the right-hand end of the line just created. Figure 12 Third Fillet. Restart the fillet command, pick the outer arc to the right of the vertical, and pick the vertical (at a point above the arc).
	Change the horizontal line ("2nd pick" in figure 12) into the WALLS layer.
Extend icon It's necessary to pick to the right of the middle of the line because AutoCAD extends the nearest endpoint to the "boundary edge".	Lastly, you will extend the horizontal line to the right edge-line. Select extend (or type EX), pick the right edge-line (this is the line you will extend to), press (end the selection process), pick to the right of the middle on the horizontal line, and finally press .

Draw the Passage Between the Bays
	Use the scroll bars to bring the bottom into view. To draw the passage-way we will firstly draw its centre line, and then use offset to get the location of the walls.
Line icon Center snap mode icon	Select line (or type L), select the Center snap mode, pick one of the arcs, type @3000,0 (to show the direction of the line), press (to end the command).
Offset icon	Offset this line 500 above and below the line - so that you end up with 3 lines, with the original in the middle.
Intersection snap mode icon Perpendicular snap mode icon	Extend the bottom line the the right edge-line! Figure 13 Bay Bottom! Select line (or type L), 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 (see Figure 13).
Trim the bottom line to remove the section to the left of the arc.	Erase the top two horizontal lines, and trim the bottom line back to the outer arc.
Break icon	Finally, use Break, to remove the arc between the remaing two lines.
Finishing the Walls!
	Before hatching the wall areas(!) you will need to close off the walls. Firstly, you'll turn off the CONST layer. Figure 14 Layers Drop-down list
These lines are needed because you must close off areas before hatching them.	Click on the layer status area, AutoCAD will display a list of the layers and their status. The first icon controls whether the layer is "on" or "off". Click on this icon beside CONST, the 'light' will go out! Then click on WALLS to close the drop-list. Figure 15 Lines to close of hatch areas. Now draw the lines identified in Figure 15, you may need to use zoom or the scroll bars to get all the lines in the view.
Hatching
Save icon	Before hatching it's often a good idea to save your drawing (select save or press Ctrl-S).
Hatch icon	Create a new layer, called hatch, and make it current, and then select hatch from the Draw toolbar, make sure the pattern type is "Predefined", and set the patern to AR-SAND, set the scale to 2, select "Pick Points", pick inside the two areas, press to end the selection process, pick "OK". AutoCAD should draw lots of dots, almost filling-in the wall area.
Note that the hatch style we are using may appear solid, but it is not! Zooming in will show that hatch is a "sand" pattern. To have the hatch "solid" simply select the SOLID style instead of "AR-SAND"...	Finally, you need to erase the three lines you added to close the wall areas so you could hatch them (see figure 15). Use the Layer Controls to turn the "HATCH" layer OFF first. If you accidentally pick the wrong thing, type: R (remove) to remove selections, and then type: A to restart adding selections. Once you've erased the three lines, turn the "HATCH" layer back ON.
If your mouse has a scroll wheel roll it and see what happens...	That completes the basic half bay! Use zoom dynamic to view the whole of the bay and then save your drawing!
Mirror the Half Bay.
Mirror icon	To mirror the section completed, select mirror from the modify toolbar (or type MI), enclose all the graphics inside the selection rectangle, press (to end the selection process), type 0,0 (the centre of the building will be the start of the mirror line), type @0,-1 (this creates a vertical line as the mirror line, this causes the graphics to be mirrored to the left), type N (don't delete the old objects). Figure 16 Completed Bay.
Duplicate the Bay
Zoom All icon Array icon AutoCAD will copy the single bay through 360 degrees, giving 8 bays!	Before continuing, select zoom-all (or type Z A), so you can see the whole drawing. Then select array (or type AR), use a selection rectangle to select the whole bay, press (end selection process), type P (polar array), type 0,0 (rotation centre), 8 (we want 8 bays!), (go all the way), Y (rotate as you go).
Last Gasps....
Save the drawing	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 - this will give you some experience erasing hatching...
Remember that there is one hatch object for each half bay...	Zoom in on the "eastern" bay (see figure 17). If AutoCAD didn't draw the hatching type REGEN (regenerate is similar to redraw, except that it forces AutoCAD to carefully recalculate the screen view, this means that curves which might to drawn "roughly" after a zoom are redrawn as smooth curves). Erase the 4 hatching objects! Figure 17 Zoom Window.
Line icon	You will now draw the centreline of the doorway, select line (or type L), select the Endpoint snap mode and pick the middle of the inner vertical wall line, then select the Perpendicular snap mode and pick the outer vertical line of the wall (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.
Trim icon	You will now use trim to take the vertical 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". Figure 18 Lines to be trimmed. Select trim (or type TR), pick the doorway lines, press (end selections), pick the vertical lines (see figure 18); and press (end the command).
It may be necessary to zoom out (or pan) before the hatching becomes visible.	Draw the lines back(!), but as two lines, instead of the four. We could draw the door, but let's not bother! Figure 19 Lines to join. Now you need to draw two lines to close off the two hatch regions. If the hatching is not visible type REGEN. Draw lines (using the Endpoint snap mode) to close off the two hatch sections (figure 19 shows one pair of line ends).
Remember to change the current layer to "HATCH"...	Now hatch the four areas!
	Figure 20 the completed drawing.
	The entry has number of stairs and there is another entry on the "western" side but we'll leave that off!
Zoom All icon Save icon	Select Zoom-all (or type Z A), so you can see the whole drawing (see figure 20). Save your drawing (select Save or press Ctrl-S). Exit AutoCAD and logoff!