I. Review of Student Work

II. Data type enables & limits functionality

• 2D: Line segments vs. Polylines (Grouped lines) vs. Area Polygon
• 3D: Surfaces vs. Surface Primitives (grouped surfaces) vs. Solids
• Appearance similar, possibilities different

III. Matching CAD methods to architectural construction .

Linear elements for skeletal wood or steel members.

• Use in structural hierarchies (i.e. member > truss > flat frame > bay module).

Surface elements for sheathing or enclosure, tensile structures

• extrusion: (pulling a shape along a straight path) metal profiles and rolled steel sections.
• lathing (drawing a shape along a circular path)
• lofting (different shapes along any path): glass-blowing.

Solid elements for concrete, weight-bearing masonry and earth-sheltered design.

• Boolean operations: union, subtraction, and intersection.
• Punctured wall from a Pinos and Miralles project by Thomas Wong

III. Surface modeling

A. Types of Surfaces

• Surface patches defined by points, lines, arbitrary curves
• Surfaces from 2D Controlled Curves (B-splines, NURBS = Non-Uniform Rational B-Splines, etc.)
• Arrays of surfaces = Meshes, manipulate with control points

B. Examples of surface functions:

• Trimming and stiching surfaces in FormZ
• Using trimming and stitching
• Trimming and Stitching meshes (Tutorial 16.5)

C. Topographical representations:

• grid of coords
• spot elvations
• contour lines
• TIN (triangulated irregular network)
• meshes

D. Pros & Cons of Surfaces

• Advantages: Model compact, reliable translation
• Disadvantages: no boolean operations, orientation matters for rendering

IV. 3D Solid modeling

A. Characteristics of Solids

• Boundary rep vs. constructive solid geometry (CSG)
• Boolean operations
• Hierarchy of boolean operations
• Substitution of primitives in CSG

TRY IT: Use Boolean operations to make an Eiffel Tower by

1. opening eiffel.fmz from Session Nine of the Course Disk
2. extruding a closed A-shape to make a long bar
3. subtracting a void
4. rotating the bar 90 degrees
5. intersecting the two.

B. Pros & Cons of Solids

• Advantages: can use Boolean operations, data contains mass information
• Disadvantages: Models more complex, Can create non-sensical data

V. Other 3D representations

Voxels (Volume elements)

• location (x,y,z) + data attributes
• medical imaging

Spaces

• Spatial nodes and links (thermal comfort, adjacency bubbles, structures)
• Space polygons and half edges as vectors (areas, centroids)

Boundaries

• Walls + connections (T,H,L,Y)
• Fractals (Recursion)

Quantities (i.e. Area calculations, Bill of Materials)

• GIS (Graphical Information Systems) : polygons or pixels + data
• Symbol library (Attributes) : located instances with data and handles

VI. Modelling Approaches

• Top down: State of Illinois Building
• Iterative refinement: Edwin Lee's skylight for Moore Ruble Yudell's Willamette Hall
• Example of hierarchical modeling.
• Bottom up: Frank Lloyd Wright concrete block study