At the end of Chapter 8, three functional diagrams were developed for the Duncan residence. The third, Diagram C, resulted from combining ideas from the other two. Diagram C can now be used as the base for drawing a few alternative form composition studies for the Duncan residence.
The first alternative is a rectangular design theme (Figure 10—79). Note how this composition relates to both the functional diagram that preceded it and the lines of force. For example, notice how certain edges of the eating area and living area relate to edges of the house, doors, and windows.
The second alternative is a combination of a rectangular theme and an arc and tangent theme (Figure 10—80). The rectangular forms are used for most of the hard surfaces, whereas arcs are used for the softer edges of the lawn and planting beds. This also makes good use of the site’s limited area and provides a good blend of structure and casualness in meeting the preferences of the Duncans.
The third alternative, Figure 10—81, combines a modified diagonal theme with a curvilinear theme. Structured diagonal forms are used for structures (walks, steps, fences, etc.), whereas softer, sweeping forms are used for the lawn edges and planting beds. The diagonal orientation of the eating and living areas in the backyard directs views from these spaces toward the planting areas along the site’s boundaries, while the flowing curves furnish motion for the eye.
I AM*L|‘ ROOM
The composition of two-dimensional forms during preliminary design is vital because it builds on the functional diagrams that preceded it while simultaneously providing the foundation for three-dimensional study. Two-dimensional forms that are pleasing to the eye yet practical to build and maintain are based on principles of sound geometric relationships among forms, a direct correlation to the functional diagrams, a respect for existing structures and site conditions, the desired character of the design, and the wishes of the client. You should know the following about form composition: 
• Potential design themes based on two-dimensional forms
Alternative circular themes and the characteristics and possible uses of each
• Characteristics of and guidelines for using a curvilinear design theme
• Guidelines for using a rectangular design theme
• Possible diagonal themes along with their characteristics and possible uses
• Characteristics and guidelines for arc and tangent and angular themes
• Reasons and guidelines for combining different design themes on one site
• Considerations for coordinating a design theme with the architectural style and features of the house
• Overall process for creating a form composition on a site
• Definition of lines of force, why they are helpful, and how they can be coordinated with the house
• Relationship between form composition and functional diagrams