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3D modeling in AutoCad - tutorial (ang)


3D Modelling in AutoCAD - tutorial exercise
The screen
The graphics area

This is the part of the screen in which the drawing will be created.

The command prompt area This area at the bottom of the screen gives you clues about your next action:Command: means that AutoCAD is expecting a new command e.g. line, arc, erase The status line Located at the very bottom of the screen, indicating current information about your drawing. The function keys can toggle between the settings. Screen Menu

This can be made to run down the right hand side of the screen, echoing the commands or options of commands chosen from the icons. It also provides the entire range of commands available. Highly recommended for beginners. An example of a parked toolbar. Snaps help you to find exact points on the drawing.

Function keys
F1 F2 F3 F7 F8 F9 F10 F11

Object Snaps

Properties Menu All elements of the drawing have properties which may be edited at any time from this menu

The Keyboard

To Cancel Press ESCAPE Escape will also remove the GRIPS (the blue squares which appear for simple editing)

Help Text screen Object snap on and off Grid on and off Ortho on and off Snap to grid on and off Polar snaps on and off Object Snap tracking on and off

To Undo Press U followed by the Return (or Enter ¿ ) key or Space The Enter key ¿ is used to:
finish off commands (e.g. Line) accept “selection sets” for Editing commands or <contents> in <> repeat the last command


Draw real sizes - scale will matter when putting your model onto paper. Think in metres or millimetres depending on what sort of object you are designing. AutoCAD measures angles (and draws arcs) anticlockwise.

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Step by Step Exercise
Setting up the drawing: Drawing Limits, Zoom All How big is your site or object? Always consider the real sizes in metres (or mm or whatever) of the overall site, in plan, measuring width then height. (x,y dimensions). This house is small, we will be thinking in metres, so it should fit into an area of 15mx12m Pick: Format, Drawing Limits Accept the lower-left limit <0.0000, 0.0000> (Press Enter ¿ ) then type in 15,12¿ to define a new upper-right limit Pick: View, Zoom, All to stretch to the new limits this has provided you with a drawing area suitable to your project, but it will not stop you extending beyond this area later Check your status line. POLAR and OSNAP should be active Pick: Line then a point near the lower left part of the screen Move the mouse to the right direction Type 6¿ 6 is the distance in metres 4¿ 4¿ From the drop-down menus Pick: Draw, Arc, Start-End-Angle Pick: point to the endpoint of the line to begin the arc. Type @4<90 ¿ (4 units straight up) Move the mouse until a full semicircle is displayed, then click again. Pick: Line and snap to the Endpoint of the arc. Complete the figure. Offset the eaves (also useful for the leaves of a cavity wall) Pick: Offset Type .3 ¿ Point at a line, then point outside the figure. Repeat for each line and arc round the figure.

Fillet the corners Pick: Fillet Type: R ¿ 0 ¿ to set fillet to a sharp point (R=radius) Pick: Fillet again Point at two lines to make them meet neatly Press Enter to repeat the Fillet command, and neaten the next pair. Repeat all round Offset the Roof ridge Pick: Offset Type: 3.3 ¿ Point at the left, vertical line, then towards the right Pick: Offset Type: 2.3 ¿ Point at top, horizontal line, then below it. Pick: Fillet Point at the two lines to make them meet at a point. (Hint - point at the parts you want to keep) Fillet and Offset are two of the most useful commands. The offset distance can be any size - across a whole site, the depth of the wall cavity.

View in 3D

Pick: View, 3D Orbit Pull the model about using the orbit cursor Right click with the mouse to see the 3DOrbit menu

Alternatively get the View toolbar: Pick: View, Toolbars,View This can be useful for returning to plan (top view) easily

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Extrude the plan

If the properties dialogue box is not yet available as illustrated on page 1, pick Properties Push the box to the side to park it

Hide the wire-frame Type hide Repeat this whenever needed Pick View, Shade, 2DWireframe to return to the wire-frame

Pick the inner, wall lines and arc so that all the blue GRIPS light up Point into the Thickness box and type 3.5¿ Press Escape twice to release the GRIPS Pick the roof ridge lines Point into Thickness box and type 5 To Erase mistakes (if or when you make some) Pick: Erase Point at the object(s) or window them (two clicks to frame them, right to left, picks up everything touched or framed) Press Enter ¿ to accept the selection

3D Faces for the roof Note that a 3D Face can only be either a quadrilateral or a triangle, nothing else. The command Region can be used for irregular shapes. Draw , Surfaces, 3D Face from the drop down menu OR: View, Toolbars, Surfaces, 3D Face Point at the four corners of one plane of the roof . Note that you do not return to the first point in order to complete the face; the third and fourth points of one face can become the first and second point of its adjacent face. Pick three points and then press Enter twice ¿¿ to form a triangle. The curved roof Find a 3D view which shows the curved end clearly Pick: Draw, Surfaces, 3DSurfaces, or pick the icon Pick: Snap to Centre Point at the arc raised for the eaves point of the cone‘s base. Pick: Snap to Endpoint Point at the arc again to give the radius of the base Press Enter ¿ Pick: Snap to Endpoint Snap to the apex of the roof Type 32 ¿ Cone to give the centre Pick:

Move the eaves up There are two good ways to use MOVE to do this: Pick Move Point at and pick all the lines outside the walls Press Enter ¿ Then either: Point at the endpoint of base of the wall (take care) Point at the endpoint at the top of the wall This is using an object on the screen to reference the distance upwards Or: having picked the lines etc, pick any point on the model, then Type: @0,0,3.5 This uses relative co-ordinates - the same X, the same Y, new Z (the distance upwards)

to accept 0 as the radius of the top to show the height of the cone to increase the number of segments

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Return to plan to erase half of the cone Pick: View, 3D Views, Plan View, World Pick: Explode Point at a line on the cone, press Enter this turns the single cone into 32 faces Pick: Erase this operation may erase extra objects, take care! See Diagram; the dotted line boxes show where to pick moving right to left. Point between segments just to the left of the vertical which should remain, but above the line of the roof ridge, and then across to the left Point between segments just to the left of the vertical which should remain, below the roof ridge, and then across to the left Press Enter ¿ Half of the cone should be gone. View in 3D again Pick: View, 3D Views, SE Isometric Erase the ridge lines Pick: Erase Point at the two lines Press Enter ¿ Define a User Co-ordinate System (UCS) We want to draw onto a surface of the model, and so we must change the orientation of the drawing co-ordinates Decide which face you wish to put a door on Make sure you have Object 2D wireframe Snaps active Pick: Tools, New UCS, 3Point Point at:3D wireframe the lower-left point of the face, (the new Origin), the lower-right point of the face (new X-direction), and then the top-left corner of the face (new Y-direction) If the UCS Icon is not attached to the face Check the properties box for UCS icon at origin

If the UCS Icon is still not attached to the face redefine it (UCS, 3point) Draw the Door Put Ortho On (either press F8 or click the status line button) Pick: Line Pick: Snap to Nearest Pick a point on the baseline to start the door Draw up and across freehand but pick Snap to Perpendicular to return accurately to the bottom line For fun, draw a circle on the face and Thicken it (Properties Box) Type hide Pick Note that you cannot see through the doorway View, Shade, 2DWireframe to return to the wireframe

Find a view which shows the face with the door Put Ortho off Pick: Erase Point at the face at its lower edge of the wall Press Enter ¿ Pick: Polyline Draw round the shape shown Type C¿ to close Pick: Region Point at the polyline. Check with Hide to see the surface

Note that the views from SE Isometric have been only projections, not true Isometric nor Perspective. 3DOrbit will produce a Perspective with Right Click mouse, Projection, Perspective.

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Return again to the usual (World) drawing plane Pick: Tools, New UCS, World Setting up a Layout for 3D modelling It is often useful to see more than one view of your model while you are creating it. The minimum would be the views: Plan, Section and 3D view. Point to Layout1 Choose a Plot Device and paper size. Erase the frame containing your model. Yes, really! You are only erasing a viewport Create more useful viewports. Pick View, Viewports, 3Viewports Press Enter twice; the 3 views appear. Double click on any viewport to activate it. This is called Modelspace. Any drawing or editing will appear in all three viewports. Indeed you can start a line in one, and finish it in another. To show an Elevation/section:Pick View, 3DViews, Viewpoint Presets Set the figure on the right to zero the pointer on the left should be set to the side you want to view. Layouts need not be regular. Single Viewports can be placed as required. Polygonal shaped Viewports can be created. Note the triangular Paperspace icon.

Saving files Save regularly (every hour or so): Pick: File, Save (or Save As if you wish to change the name or drive e.g. H: ) Point at the little arrow and scroll up or down to find the drive, then pick a folder to save you drawing in. Change the name in the File name box if you wish. There is an automatic save which may rescue you from emergencies. Ask for help before panicking Leaving the programme Pick: File, Exit if you have not SAVEd recently it will ask if you wish to save the changes to the drawing

Shut down the machine before leaving the room - it is vital that you shut down elegantly - the Network works better for us all if everyone logs out neatly.

In this exercise you have used the following commands:Drawing Line Arc Circle 3dFace 3Dsurfaces - a cone Polyline Viewing Zoom Viewports 3Dviews 3dOrbit Hide Shade Editing Erase Explode Move Offset Fillet Region You have also made Viewports, and switched between Modelspace and Paperspace. You have used the Properties box to edit the Thickness of lines, arcs and circles. Most importantly, you have learned to change UCS so that you can draw in several planes. You should be able to model almost anything!

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AutoCAD provides some ways of making interesting surfaces.

Keyboard Shortcuts
Command Keyboard Menu (drop-down unless otherwise indicated) Draw, Arc, various options Modify, Array, rectangular or polar Draw, Circle, various options Modify, Copy Format, Drawing limits Modify, Erase, Select Files, Exit Modify, Extend Modify, Fillet Tools, Drafting settings, grid Draw, Line Modify, Mirror Modify, Move Modify, Offset Files, Open View, Pan Draw, Polyline View, Redraw Files, Save As Files, Save Tools, Drafting settings, snap Modify, Stretch Modify, Trim View, 3Dview Format, Drawing limits View, Zoom Dynamic Previous Extents Window All


They all require 2D or 3D Polylines. Draw the plines, then get the Surfaces Toolbar, or find them in the Draw, Surfaces drop down menu. They are limited by two variables; Surftab1, and Surftab2 which control the number of 3D Faces generated. If the surface you get is wrong, erase it, change the Surftabs and try again.
Revsurf, or Surface of Revolution

requires one Polyline profile, and an axis round which to rotated the profile. Surftab1 and Surftab2 will affect the number of faces created.(Type Surftab1(or 2) at the Command prompt to give it a new number)


Tabsurf or Tabulated Surface

extrudes a polyline along the path of a straight line. Surftab1 will be used.
Edgesurf or Edge Surface

will construct a mesh between 4 3Dpolylines which must meet exactly. Surftab1 and Surftab2 can have a crucial effect Surftab1 affects the first polyine chosen.


Rulesurf or Ruled Surface

draws a series of 3dfaces between two polylines. Take care in selecting two lines, the surfaces can get twisted. Surftab1 should be set suitably In all cases a more flexible surface is constructed if the polylines have been smoothed first. Often it works best if the polylines and lines are on a different layer from the mesh.

Arc a Array array Circle c Copy cp Drawing limits limits Erase e Exit Extend extend Fillet fillet Grid F7 Line l Mirror mirror Move m Offset offset Open Pan p Polyline pl Redraw r Save As Save save Snap F9 Stretch stretch Trim trim Viewpoint (3D view) vpoint Limits limits Zoom z d p e w a


Alison Murison June 2000

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