Surface Modeling - Engineering Design Graphics - Lecture Slides, Slides of Engineering Drawing and Graphics

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Engineering 22

Surface

Modeling - 1

Learning Goals

• Use AutoCAD Built-In Commands to make

“Primitive” 3D Surface-Shapes

• Box, Sphere, Cone, Pyramid, others
• Draw Surface of Revolution using a Shape &

Axis

• Connect two Shapes with Straight Lines to

Make “Ruled” Surfaces

• Build Complex 3D Shapes by Adding &

Subtracting Primitives

Draw Box

 Pick Length & Width

Using Ortho-Snap and

Mouse

 Specify Height from

KeyBoard

 “ENTER” To NOT

Rotate

Command: _ai_box Specify corner point of box: Specify length of box: Specify width of box or [Cube]: Specify height of box: 7 Specify rotation angle of box about the Z axis or [Reference]:

Draw Wedge

 Add to End of Box

 Pick Length Using

Ortho-Snap and Mouse

 Pick Width and Height

using END Option to

Pick Box Corners

 “ENTER” To NOT

Rotate

Command: ai_wedge Specify corner point of wedge: >> Specify corner point of wedge: end of Specify length of wedge: Specify width of wedge: end of Specify height of wedge: end of Specify rotation angle of wedge about the Z axis:

Draw Triangle-Base Pyramid

 Triangle Pyramid → a

TETRAHEDRON

 Enter Pts From KeyBd

Command: _ai_pyramid Initializing... 3D Objects loaded. Specify first corner point for base of pyramid: 0, Specify second corner point for base of pyramid: 8, Specify third corner point for base of pyramid: 2, Specify fourth corner point for base of pyramid or [Tetrahedron]: t

Draw Ridged Pyramid

 Base & 2-Sides →

Quadrilaterals

 Ends → Triangles

 Enter Pts From KeyBd

Command: ai_pyramid Specify first corner point for base of pyramid: 0, Specify second corner point for base of pyramid: 10, Specify third corner point for base of pyramid: 10, Specify fourth corner point for base of pyramid or [Tetrahedron]: 0, Specify apex point of pyramid or [Ridge/Top]: R Specify first ridge end point of pyramid: 3,5, Specify second ridge end point of pyramid: 7,5,

Draw Dish

 Enter Pts From KeyBd

 This is a SEMIsphere;

Could Also make

• Full Sphere
• HEMIsphere (dome)

Command: _ai_dish Specify center point of dish: 5, Specify radius of dish or [Diameter]: 8. Enter number of longitudinal segments for surface of dish <16>: 17 Enter number of latitudinal segments for surface of dish <8>: 11

Draw 3D Face

 3DFaces are flat

surfaces with 3 or 4 straight edges.

Command: _3dface Specify first point or [Invisible]: 0, Specify second point or [Invisible]: 10, Specify third point or [Invisible] : 10, Specify fourth point or [Invisible] : 0, Specify third point or [Invisible] : 0,10, Specify fourth point or [Invisible] : 10,10, Specify third point or [Invisible] : 10,15, Specify fourth point or [Invisible] : 0,15, Specify third point or [Invisible] :

RevSurf Example

Axis of Revolution

Form to Revolve

 Make Bowl with a Nice

Base by

Revolving a Closed-Form

About a Vertical Axis

Set SHADING & SurfTab

• Increase the WireFrame

Density Command: surftab

Enter new value for SURFTAB1 <6>: 36

Change to IsoMetric View

Invoke RevSurf

Select object to revolve: Select object that defines the axis of revolution: Specify start angle <0>: Specify included angle (+=ccw, -=cw) <360>:

Object to Revolve

Object that defines the axis of Revolution

SurfTab Comparison

• SurfTab2 = 6 • SurfTab2 = 12

Tabulated & Ruled Surfaces

 Set Up:

• Shade Mode →

Gouraud Shaded,

Edges on

• SurfTab1 Value → 8

Command: _shademode Current mode: Gouraud+Edges Enter option [2D wireframe/3D wireframe/Hidden/Flat/Gouraud/fLat+edges/gOuraud+edges] <Gouraud+Edges>: _o Command: _shademode Current mode: Gouraud+Edges Enter option [2D wireframe/3D wireframe/Hidden/Flat/Gouraud/fLat+edges/gOuraud+edges] <Gouraud+Edges>: _o Command: surftab Enter new value for SURFTAB1 <6>: 8