d e p a r t m e n t   o f   a r c h i t e c t u r e ,   u n i v e r s i t y   o f   o r e g o n

- To understand how CAD systems allow us to view, generate and edit 3D objects.

- To be able to use AutoCAD¼s coordinate systems, viewing controls, geometric transformations

- To understand the differences between surface and solid modeling

0. Special Guest: William Seider of WBGS Architecture and Planning PC.

I. Multiple Views: TV cameras aimed at a model

- Multiple 2d views clarify depth relationships.

II. Digital 2D views of 3D space: Shifting the point of view

- View menu > VPOINT > Presets

- Defining the viewing vector with VPOINT (x,y,z) which defines the tail of the viewing vector pointed at (0,0,0)

B. Perspective projection: Interactive viewing with DVIEW

- Manipulating Camera and Target

- Creating perspectives (converging rays) with a finite DVIEW / Distance

III. Grids in space

Construction planes and co-ordinate systems (x,y and z axes) give order. A. World Co-ordinate System (WCS) based at 0,0,0 with standard x,y, z B. Defining User Co-ordinate Systems (UCS): invisible drawing surfaces, references for editing functions. - Settings menu > UCS > Presets OR type DDUCSP (sometimes buggy: watch RELATIVE or ABSOLUTE) - PLAN orients the view to the current UCS

IV. Activity I: Viewing

1. Open "site-3d.dwg" in the AutoCad folder > Sample folder (should be in Paperspace).
   
2. Change to View menu > Model space. Tap on each image to activate it, then try out VPOINT (View menu > Viewpoint > Presets) See if you can spin the model, then try moving down to eye level.
   
3. Get out of the plot layout mode (VIew > Tilemode > On) and try creating your own screen layout
   (View menu > Layout > Tiled Viewports)
   
4. Experiment with DVIEW / Camera and DVIEW / Distance to create an eye-level perspective:
   A. View menu > DVIEW / Ca
   

   Select objects: [window two sections of the house for orientation & hit Return]
   

   Angles correspond to Vpoint Presets diagram (try 3 degrees to get a realistic eyepoint, then spin the model to -120 degrees from the x axis)

   Hit Return to exit.

   
   

   B. Type DVIEW
   

   Select objects: p (this recalls the previous selection set), hit Return
   

   Type DI to change the viewing distance to 150'.

V. Activity 2: UCS's and modeling

From the Course Disks folder > 3D ORTHOHSE folder > Open ORTH-UCS.DWG.

Change the UCS's to insert the elevation blocks correctly.

Answer the following questions:

How can we generate 3D forms from 2D?

What are different primitive elements and different types of 3d Modelling

1.

2.

3.

VI. Drawing and editing in 3D space

A. 3D Surface entities: Creating planar skins 1. Sweeping profiles through space Extrusion (Tabulated surface or TABSURF) Surface of revolution (REVSURF) 2. Defining a three-dimensional element with boundaries: - 4 corners (3D Face or 3DFACE) - More than 4 corners (PFACE) - End edges (Ruled Surface or RULESURF) - All edges (Edge defined patch or EDGESURF) 3. Selecting predefined surface 3D Objects

B. 3D Solids from Model menu

Method 1: Building up primitives (Quick and Dirty)

• VPOINT (3,-5,4) makes the view an axonometric
• GRID, SNAP and OSNAP provide basic accuracy
• Draw a vertical line „@0, 0,20¾ as a guideline for defining UCS¼s
• Surface model:
  
  Insert 3D Objects
  
  CHPROP (Thickness) of 2D drawing entities to extrude

  Solid model: Use Advanced Modelling Extension (AME) through Model menu.

Method 2: Building from a Glass Plane model of 2D drawings (Very accurate)

• Reorganize layers so that each orthogonal view can be separated.
  
• Save the orthogonal views separately with WBLOCK
  
• Define UCS's with 3 points and Save them (FRONT and SIDE, typically)
  
• Divide the screen into multiple windows with VPORTS
  
• Set-up views with VPOINT or PLAN
  
• Save views with VIEW (Save)

• For each orthogonal view, switch the UCS to the correct plane.
  
• Insert the block of each view into the correct 3D location. Adjusting colors and layers if necessary.
  
• Use the unexploded orthogonal views for measuring and tracing. Trace elements from the 2d block and move the new lines into the appropriate planes. Connect these lines to edges in the third dimension.
  (As you get more adept, you can explode the block and move the elements into place without tracing. Having a copy of the unexploded block gives a fixed guide.)
  
• As you build up the wire-frame, separate the 3D lines into different layers to reduce confusion.

• Keep the model precise by setting the OSNAP defaults to END and INT.
  
• Where possible, copy lines whose geometry is accurate rather than drawing freely in space. This assures that the orientation of the lines is correct.
  
• Start with the major masses of the building. Block out the most abstract forms first, then add detail.
  
• Use 3D blocks and arrays for repetitive elements.

VI. Exercise on Boolean Operations with Solids (Thursday)

VII. Reading: "Frames in Space"

Chapter 9 from Mitchell, William J. and M. McCullough, Digital Design Media, Van Nostrand Reinhold, 1995.