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

Organizing CAD Information

April 15, 1997

Objectives: - To understand the following kinds of organizing tools and how to use them:

construction lines
precision control tools (object snap, grid snap, ortho lock)
layers
symbols

O. Q & A, Review

You should be familiar with the following:

File Commands: New, Open, Saveas, Save, Exit (End / Quit)
Coordinate system input: Absolute 0,5 vs. relative @0,5 coordinates (use relative coordinates mostly); Polar Coordinates 5<90 means radius 5, angle 90
Drawing Graphic primitives: Arc, Circle, Line, Pline, Rectang, Polygon
Creating Selection Sets: All, Window, Crossing, Last, Undo, Window, Previous, Add and Remove.
Editing with Geometric Transformations:: Move, Copy, Mirror, Rotate
Setting up a drawing (may be new to you: see Katz Ch. 5): UNITS, LIMITS, SNAP, ORTHO

I. Concept: CAD Organization parallels Architectural Organization

A. Geometric ordering devices:

Construction Lines & Grids: Regulating lines
Orders of Symmetry
Repetitive elements and rhythm

B. Geometric Refinement: Palazzo composition

Customizing end conditions, central axis
Acknowledging gravity: base, middle and top
Adjusting proportions: parametric variation

C. Using hierarchical symbols (nested Blocks)

II. How-to: Construction Lines & precision drawing assistants

Add value by ordering the information. A CAD drawing of a building should be reflect its organization. The geometry should follow how the original designer thought of the architecture.

A. Construction lines or Regulating Lines provide the framework for creating a drawing. Use OFFSET to generate parallel lines.

B. Object Snap (OSNAP) locks point selection to specific parts of entities. Use OSNAP all the time for precision!!

CEN Center of arc or circle
END Endpoint of line or arc
INT Intersection
MID Midpoint of line or arc
NEA Nearest point on line, arc, or circle
QUA Quadrant points of a circle
PER Perpendicular from last point to object

C. Settings for precision drawings:

SNAP (F3) locks all points to an imaginary grid, controlling the drawing's tolerance.
GRID (F5) displays a reference grid of dots at a specified spacing, without locking points.
ORTHO (F4) constrains the point selection to the orthogonal: along either the vertical or horizontal axis.

III. Using Layers to separate plotting Lineweight and Linetype

Organizing adds value:

Separating information into different layers is like using different pieces of tracing paper for different kinds of elements. Organize layers

By building system (similar to CSI categories): foundation, columns, beams, exterior walls, windows, doors, interior walls, ducts, pipes, etc.

By graphic lineweight (thickness) and LINETYPE (pattern)

By materials for rendering: Concrete, steel, white plaster, green paint, wood, clear glass, etc.

A. LAYERS Description

B. Plotting

- Units: draw in real scale and plot at a reduction such as 1:100
- Actual Dimensions vs. Viewing and Plotting Scales
Screen and printed views are camera zooms on an static 1:1 scale model
- After entering the command PLOT, make sure your device (choice of which kind of plotter) is correct.
- Each color line will be mapped to a Pen Number with a certain line thickness. For the HPLaserjet, you need to give the line width in mm.
- Choose what you want to plot: the whole screen "Display", or a "Window" which can be interactively selected off the screen. Saved Views can also be plotted, saving time.
- Drawings are created in real scale, so you must specify the output scale when you plot: the ratio of plotted mm or inches to the drawing unit (m, feet, etc.)
- Check the scale and orientation are correct with Preview..."Full". Do not "Fit to Paper", because then you cannot measure off the print.
- On the Mac, make a plot file with the "Plot to File" command. Instructions which tell the printer or plotter what to do will be stored into a *.plt file.

III. Drawing a simple plan step by step

A. Method

- Set LIMITS, UNITS, OSNAP default to end, int, ZOOM Extents
- Plan LAYERS and load LINETYPES.
- Turn on ORTHO and draw two LINEs, one horizontal and one vertical, larger than your building.
- Create additional parallel construction lines at precise distances by using OFFSET.
- Changing to a new layer, draw using construction line INTersections.
- TRIM, FILLET and EXTEND to neaten.
- ERASE unnecessary construction lines.
- PLOT to scale

IV. Concept: Using symbols and construction lines for design refinement.

- Definition of types sets out what elements will be used repeatedly.
(In AutoCad, BLOCK defines a stretchable rubber stamp.)
- Instantiation of types puts in copies of the original definition.
(AutoCAD's INSERT locates and sizes each copy of the block.)
Nest elements into a HIERARCHY, a prioritized tree structure
- Use substitution (replacement) or global replacement of elements to try alternatives. (In AutoCAD, redefine the original element with BLOCK).
- Use transformation or parametric variation (stretching, shrinking or changing a quantity) to adjust the basic elements to good proportions.

V. Symbols in AutoCad: Blocks

Summary of Relevant AutoCAD commands:

BLOCK: Groups primitive entities under a name for future insertion.
WBLOCK: Saves the contents of a block definition onto an external drawing file.
INSERT: Allows you to place a previously defined block into a drawing.
EXPLODE: Replaces a block with the original component entities that comprise it.

VI. AutoCad Blocks exercise

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