3d Modelling Using Autocad-chapter 9a

8/17/2019 3d Modelling Using Autocad-chapter 9a

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AUTOCAD3D: MODELLINGCHE 414 Engineering Drawing


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The Age of Computers


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3D Drawing• 3D Coordinate

• Basic Solid Models

• (Box, Sphere, Cylinder, Cone, Wedge, Torus)

• Basic Techniques for 3D Modeling• (Revolve, Extrude, Union, Subtract, Intersect)

• Editing Tools

• (Chamfer, Fillet, Align)


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Types of 3D models

Wireframes

Solid Models

Surface models


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Wireframe Models

• 3D model createdwith ordinary lines,

circles, arcs, etc., to

represent edges

• Only vertex and edge

data is stored

• No shading, hidden

line removal


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Surface Models

• Model with surface objects• Meshes frequently used to

represent surfaces

• Surface, edge, & vertexinformation stored

• Shading, hidden line

removal

• Useful for modeling shapes

with complex curvature

(e.g., hull forms, airfoils,

automobiles)

(10,100,100)

(0,0,0)

X

Z

Surface Model

- 6 meshed surfaces


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Solid Models

• Model with solid objects(e.g., primitives, sweeps)

• Database containsinformation about vertices,

edges, surfaces, and thespace enclosed by thesurfaces• Mass and material

properties• Interference checking

• Shading and hidden lineremoval

(100,100,100)

(0,0,0)

X

Z

Solid Model

- 1 primitive


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3D Display

• Wireframe

• Hidden line / hidden surface

• Shaded

• Rendered

NOTE: Display refers to the way that 3D objects

appear on the display device (i.e., thecomputer monitor)


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Wireframe Display

• Model edges and contours are visible

(Model may be wireframe, surface, solid or

parametric)

• Simpler and faster than shaded display

• Trade-off between complexity and speed


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Hidden Line/Surface Display

Hidden line/surface removal - class of algorithmsused to determine model edges, surfaces, or volumes

that are visible or invisible from a particular viewpoint

Without hidden lines removed With hidden lines removed

wireframe wireframe

surface surface

solid solid


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Shaded Display

Display technique that hideshidden lines and applies flat

colors to visible surfaces


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Rendered Display

Single, shaded view of a3D model to which

colors, materials,

textures and lighting

have been added


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3D TOOLBARS

• The toolbars in AutoCAD 2007 are calledModeling, Solids Editing, and Render . Inthis session, we will discover the methods of

using Modeling and Solids Editing toolbars.• Rendering will be discussed in more detailedin the next session.

• If you are using any one of the earlier

versions of AutoCAD, there are no Modelingtoolbar. The tools are put in two differenttoolbars called the Solids and Surfaces toolbars.

CHE414 ENGINEERING DRAWING 13


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3D ISOMETRIC VIEWS• From View dropdown menu, click on 3D Views to select the

different isometric views, OR click on appropriate icons on Viewtoolbar.

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The HIDE Tool

• Command: hide or hi

• Or from View dropdown menu,

• Or from Render toolbar.



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Exercise 1

• Command: 3dface

• Specify first point or [Invisible]: 60,230• Specify second point or [Invisible]: 60,110

• Specify third point or [Invisible] :190,110,150

• Specify fourth point or [Invisible] : 190,230,150

• Specify third point or [Invisible] : ENTER

• Command: mirror

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All you see now is this. Pretty disappointing isn’t it?

Mirror the object at mirror

line 190,110 and 190,230

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• Now, view SW Isometric.

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60,110

60,230

190,230,150

190,110,150

Before hide After hide



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Viewed in 3D Modelling




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Exercise 2




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Viewed in 3D Modelling




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3D Primitive Solids




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ISOLINES• The isolines system variable will affect the

appearance of the solid model. The higher the settingthe smoother the object will appear.

• The higher the value, the longer AutoCAD takes tocalculate and regenerate the model, and this will slow

down your computer.• Tip: keep the isolines setting low while working on themodel. When you’re done, you can set the numberhigher.

• In older versions of AutoCAD, the function is calledSURFTAB1 and SURFTAB2.



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SURFTABCommand: surftab1Enter new value for surftab1: 16

Command:

Command: surftab2

Enter new value for surftab2:

Command: regen



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ISOLINES 4 ISOLINES 16


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Revolved Surface

• Construct the outline

using Polyline. Add

the horizontal line

using Line.• Use Revolved Surface

tool.

•See instructions inhandouts.



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REGION TOOL• Construct this outline.

• Before attempting to construct 3D

models, lines must be converted

into polylines or into regions.


Command: regionSelect object: window the drawing

Select object: ENTER. Region is created



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EXTRUDE TOOL

• We will use the previous outline.

• 3D View the object.

• Hide.


Command: extrude

Current wire frame density: ISOLINES=4

Select objects to extrude: 1 foundSelect objects to extrude:

Specify height of extrusion or

[Direction/Path/Taper angle] : 50


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POLYSOLID• This is a new command for AutoCAD 2007. A

polysolid allows you to draw a solid object whiledefining the height and the width.

• This command is probably aimed at thearchitects, who will enjoy the ability to quicklydraw solid walls.



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Pyramid Example

• Command: _ai_pyramid

Specify first corner point for base of pyramid :

340,230

Specify second corner point for base of pyramid :

430,230

Specify third corner point for base of pyramid :

430,310

Specify fourth corner point for base of pyramid :340,310 Specify apex point of pyramid or

[ridge/top]: 385,270,260



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• Draw some primitive solids using the dimensions shown

above or make up your own. Try to create a building out

primitive solids.




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THE SOLIDS EDITING

TOOLS

AUTOCAD 2007The Boolean Operations

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To explain the funny name : "It was named after

George Boole, who first defined an algebraic system of

logic in the mid 19th century."



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COMMAND INPUT ICON DESCRIPTION

UNION

(Boolean)UNI

Joins two or more solids into creating one

based on the total geometry of all.

SUBTRACT

(Boolean)SU

Subtracts one or more solids fromanother creating a solid based on the

remaining geometry.

INTERSECT

(Boolean)IN

Creates a single solid from one more

solids based on the intersected geometry.

EXTRUDE FACE SOLID EDITAllows you to increase the size of a solid

by extruding out one of its faces.

SLICE SLICE Slices a solid along a cutting plane.

3D ALIGN 3DALIGN Aligns 2 3D Objects in 3D space.

• AutoCAD has some

commands that make this

easy for you.

• These are the boolean

operations as well as someother helpful commands for

solids editing.:

Working in 3D usually involves the use of solid objects. At

times you need to combine multiple parts into one, or remove

sections from a solid.



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UNION• Below left, there is a box and a cylinder. These are two

separate objects. If you want to combine them into one object,

you have to use the union command.

Command: UNION

Select objects: 1 found

Select objects: 1 foundSelect objects:

NOTE: The object that you select first will determine the properties of the

united object when it is created.

The UNION command

combines one or more solid

objects into one object.



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SUBTRACT

• The subtract command is used to cut away/remove the

volume of one object from another. Here is an example:

*Remember that AutoCAD always asks for the object that you are

subtracting FROM first, then it asks for the objects to subtract.

Command: SUBTRACT

Select solids and regions to subtract from...


Select objects: Select solids and regions to subtract...Select objects: 1 found

Select objects:

The SUBTRACT command

removes the volume of one or

more solid objects from an

object.



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INTERSECT

• This command creates a new solid from the intersecting

volume of two or more solids or regions. AutoCAD will findwhere the two objects have an volume of interference and

retain that area and discard the rest. Here is an example

of this command shown below:

Command: INTERSECT



Select objects:

The INTERSECT command

combines the volume of one or

more solid objects at the areas of

interference to create one solid

object.



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SLICE

• This command does exactly what the name

implies. You can slice a 3D solid just like youwere using a knife.

Command: SLICESelect objects: 1 found

Select objects: Specify first point on slicing plane by

[Object/Zaxis/View/XY/YZ/ZX/3points] : PICK POINT 1

Specify second point on plane: PICK POINT 2

Specify third point on plane: PICK POINT 3

Specify a point on desired side of the plane or [keep Both sides]:

This is a very useful command - think of it as a trim in 3D. Make sure you have

your Osnaps on for this command and that you pick the correct points. In a

complex 3D drawing, this can be tough to see.



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3D ALIGN• Sometimes, you may find it faster or easier to draw

something separately and then move and align it intoplace. The command to use this in 3D is 3DALIGN.

The goal will be to align the cylinder on the front face of

the box where the dotted line is.

The finished 'alignment job'

should look like this after using

the hide command.



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EXTRUDE FACE

• Works just like EXTEND in 2D drawing, this is just likestretching a 3D object.

• The command is quite easy to use, but you need to be

careful on which face you select.

• Not to be confused with Extrude Objects.



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NOW LET’S TRY SOME

EXAMPLE EXERCISES!END OF SLIDE



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Getting started with 3D

• When you start AutoCAD, by default you see aWorkspaces dialog box that asks whether you

want to work in the old 2D environment (AutoCAD

Classic) or in 3D (3D Modeling).



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Changing the viewpoint to view the 3D models

• Previously, in 2D drawing, entities are drawn in

the Plan view. Objects are viewed from the

direction of the positive Z-axis• To view 3D models, viewpoint needs to be

change so that the object is displayed in the

space with all three axes

• 3 methods available: DDVPOINT command,VPOINT command and View toolbar


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Plan view – 2D view

3D view


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Using the DDVPOINT command

Select: Menu > View > 3D Views > Viewpoint PresetsOr Command: DDVPOINT

this command sets the viewpoint to view the 3D models

• Viewpoint is set with respect to the angle in the XY

plane and the angle from the XY plane.

+Z+Y

+X

View direction

Angle from

XY plane

Angle in the

XY plane


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When DDVPOINT is invoked,

the Viewpoint Presets dialog boxappears

Absolute to WCS: to set

viewpoint with respect to the

world coordinate system

Relative to UCS: set the

viewpoint with respect to the

current user coordinate system

WCS = world coordinate system: default set by AUTOCAD, x,y,z are

measured with reference to the fixed origin (0,0,0)

UCS = user coordinate system: coordinate set by user, by shifting the XY

plane to the desired location


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Angle in the XY plane: 225

Angle from the XY plane: 30


Angle from the XY plane: 25

Viewing the 3D model using the DDVPOINT Command


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If negative angle from XY plane, the Z-axis will be displayed in

the dotted line


Angle from the XY plane: -25 Angle in the XY plane: 225 Angle from the XY plane: -25


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Using the VPOINT command

U i th Vi T lb


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Using the View Toolbar


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Basic Solid Models


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3D coordinate Systems

+Z+Y

+X

(10,6,6)

Distance along z-axis

Distance along x-axis

Distance along y-axis

Origin (0,0,0)

Two main types of coordinate systems:1. Absolute coordinate system

Command: LINE

Specify first point: 0,0,0

Specify next point or [Undo]: 10,6,6

Specify next point or [Undo]:


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Two main types of coordinate systems (continued):

2. Relative coordinate system.• there are 3 coordinate system of this type

• relative rectangular coordinate system

@ X coordinate, Y coordinate, Z coordinate

• relative cylindrical coordinate system@ distance from the reference point in the XY plane


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Front view of the model

Side view of the model


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To begin drawing the above model:

1. Choose SW Isometric view

2. Choose Draw > Line

Specify first point: 4,2,0

Specify next point or [Undo]: @0,0,2


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Specify next point or [Undo]: @3,0,0

Specify next point or [Close/Undo]:@0,0,2

Specify next point or [Close/Undo]: @3,0,0

Specify next point or [Close/Undo]: @2


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Basic Solid Models

Follow the Instructions

• Open a new drawing

• Change the display to SE Isometric View

(View → 3D Views →SE Isometric)

• Select the Box button Specify corner of box or [CEnter] : 4, 4, 0

Specify corner or [Cube/Length]: L

Specify length: 4

Specify width: 4

Specify height: 2

• Select the Cone button

Specify center point for base of cone or [Elliptical] : 6, 6, 1

Specify radius for base of cone or [Diameter]: 2

Specify height of cone or [Apex]: 4

• Select the Cylinder button


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• Select the Cylinder button Specify center point for base of cylinder or [Elliptical] : 6, 6, 4

Specify radius for base of cylinder or [Diameter]: 1.5

Specify height of cylinder or [Center of other end] : 2.5

• Select the Sphere button Specify center of sphere : 6, 6, 7.5

Specify radius of sphere or [Diameter]: 1.5

• Select the Torus button Specify center of torus : 6, 6, 5

Specify radius of torus or [Diameter]: 1.5

Specify radius of tube or [Diameter]: 0.25

• Create another Torus with center (6,6,9), radius of torus equals to -1.5 and radius of tube equal to 2.

• Select the Wedge button Specify first corner of wedge or [CEnter] : 4, 4, 2

Specify corner or [Cube/Length]: 5, 5, 2 Specify height: 5

• Create another Wedge with corner at (8,8,2) and (7,7,2) with heightequals to 5.


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Creating a complex solid model

Documents

3d Modelling Using Autocad-chapter 9a