Chapter Four. Implementation of the SpaceMaker

Transcription

1 38 Chapter Four Implementation of the SpaceMaker This chapter describes the SpaceMaker, a symbol-based 3-D computer modeling tool. Users make 2-D freehand sketches, draw symbols in the sketches, and SpaceMaker then converts the sketches into 3-D models that can be viewed in VRML format on the web. The SpaceMaker is based on two assumptions. First, designers use different drawing conventions such as text labels in their freehand drawings to indicate different design concerns. Second, those drawing conventions can serve not only as clues to infer designer s intentions about relationships of architectural spaces, but also as clues for the modeling tool to insert appropriate architectural elements corresponding to the designer s spatial concept. The prototype SpaceMaker program described in this chapter was built to explore how the use of drawing symbols can help designers make 3-D digital models in the early stage of design process. The implementation of the SpaceMaker is guided by the four premises: 1. A modeling tool should allow designers to make freehand floor-plan drawings to explore spatial layouts. 2. A modeling tool should allow designers to apply personal drawing symbols in freehand drawings in order to identify different functions. 3. A modeling tool should convert freehand drawings into 3-D models according to the drawing symbols. 4. A modeling tool should provide designers the ability to further modify the converted 3-D models, thus maintaining the flexibility of early schematic design.

2 The chapter is divided into six sections: Section 4.1. first explains the SpaceMaker s system architecture. Section 4.2. describes the SpaceMaker s freehand drawing environment and recognition systems. Section 4.3. describes how to define a symbol. Section 4.4. introduces the tools for modifying a converted model. Section 4.5. explains the conversion from 2-D to 3-D, and finally Section 4.6. briefly discusses the strengths and weaknesses of the current implementation System Overview System Architecture The SpaceMaker acts as an assistant that provides designers 3-D spatial information for further modifying design concepts by making 3-D digital models based on designer s use of symbols in the drawings. (Figure 4.1) Figure 4.1 shows that the SpaceMaker acts as an assistant providing 3-D information to designers. The SpaceMaker is a 3-D digital modeling tool. It consists of several parts: a freehand drawing environment with recognition, a symbol definition system, a 3-D model conversion system, and a model modification system. Figure 4.2 illustrates the SpaceMaker system architecture.

3 40 Figure 4.2 shows the SpaceMaker system architecture. Freehand Drawing Environment with Recognition The SpaceMaker allows designers to make freehand sketches in the Sketch Board (user interface described in the following section), including boundary lines, partitioning lines, and symbols. Its Recognition System, which consists of three recognizers: Boundary Locator, Partition Locator, and Space Locator, then recognizes the sketches and displays the result in the Space Window in a 2-D floor-plan format. Symbol Definition System The Symbol Definition System allows designers to establish a pre-defined symbol template that provides information for the symbol recognizer (Space Locator). Designers draw a symbol in the Symbol-Sketch Window, and define the symbol by assigning it a set of spatial parameters in the Symbol-Definition Window. 3-D Model Conversion System

4 The 3-D Model Conversion System translates the result from the Recognition System into a 3-D VRML format. Designers can thus view the model in 3-D through a VRML-enabled web-browser. 41 Model Modification System The SpaceMaker s Model Modification System provides designers several tools to further modify the converted 3-D model. Designers can change the spatial configuration of the entire building or use tools in the Model Modification Window to change the characteristic of any single element in the building User Interface Overview Figure 4.3 shows the SpaceMaker user interface, which consist of four tool palettes and five windows: the Sketch Board, Space Window, Symbol-Sketch Window, Symbol- Definition Window, and Modification Window. Tool Palettes There are four palettes in the SpaceMaker. The TOOLS palette consists of all command buttons for making freehand sketches. The SPACE palette contains all command buttons for converting sketches into models. The MODIFY palette manages file saving and translating tasks and it also contains command buttons for modifying models. The COLORS palette allows users to distinguish different spaces with colors. Sketch Board The Sketch Board displays freehand strokes drawn by a user with a mouse or a digitizing tablet and a stylus. Freehand stroke inputs may include freeform lines, bubbles, and symbols.

5 42 Figure 4.3, The SpaceMaker User Interface. Space Window The Space Window displays the floor plan of the interpreted sketch, which is the 2-D projection of the 3-D model that the SpaceMaker generates. Symbol-Sketch Window To define a symbol, a user must first draw it in the Symbol-Sketch Window.

6 Symbol-Definition Window The Symbol-Definition Window contains buttons used to define the architectural interpretation of a symbol, which users draw in the Symbol-Sketch Window, in terms of wall elements and boundary conditions. The Symbol-Definition Window also provides users a preview of their selection of wall elements. 43 Modification Window The Modification Window contains buttons used to modify the boundary conditions of spaces in the model. An elevation view of a wall is displayed when users choose a wall in the model to be modified Freehand Drawing Environment with Recognition Freehand Drawing Environment The SpaceMaker is a freehand drawing environment. Designers use a mouse or a stylus with a digitizing tablet to make freehand sketches and to draw symbols into the sketches. Data input by users is then examined by the SpaceMaker and categorized into three different types: exterior building boundary, interior partition walls, and drawing symbols. Each of three types of data will then be respectively handled by independent recognition systems: a building-boundary locator (Boundary Locator), a partition-wall locator (Partition Locator), and a symbol recognizer. The symbol recognizer also acts as an interior-space locator (Space Locator). Figure 4.4 shows the structure of the recognition system.

7 44 Figure 4.4 shows the structure of the recognition system. Sketching data is categorized into three types and then handled by three different recognizers Recognition Systems Locators for Building Shape and Partition Walls The studies of freehand drawings described in Chapter Three reveals that designers may start sketching to enclose and locate the entire building boundary. Designers then divide the floor into several individual rooms by either using lines or bubbles. Therefore, the SpaceMaker follows the sequence of making freehand sketches to first identify the building boundary and then to locate partition walls that divide the entire floor into several spaces. The SpaceMaker has two simple freehand sketch recognizers, the Boundary Locator and the Partition Locator, which respectively identify and locate the building boundary and interior partition walls. The Boundary Locator receives the first freehand stroke and identifies it as the boundary of a building. Typically, an architect draws a rough envelope to indicate the building boundary. The SpaceMaker receives the envelope and creates a smallest rectangular frame that contains the entire freehand envelope. The Boundary Locator then identifies the four corners of this rectangular frame and conceives this frame

8 as the boundary of the building that the designer will work with 4. Figure 4.5 shows that the Boundary Locator recognizes a freehand envelope stroke and identifies it as the building boundary. 45 Figure 4.5, Boundary Locator recognizes a freehand envelope stroke and identifies it as the building boundary. After drawing the boundary envelope, designers can further divide the entire floor by drawing either sketch lines or bubbles. When a user draws a line on the Sketch Board, the Partition Locator receives it and first identifies the orientation of the line by examining whether the line runs horizontally or vertically. The Partition Locator also identifies the position of the line and marks it with a guideline both on the Sketch Board and Space Window. Figure 4.6 shows how Partition Locator recognizes several freehand lines and identifies them as interior partition walls. 4 Currently, the SpaceMaker only supports simple rectangle-shape recognition. Any freeform envelope stroke by users, no matter how complex it is, is translated to a simple rectangle by the Boundary Locator.

9 46 Figure 4.6, Partition Locator recognizes several freehand lines and identifies them as the interior partition walls. Alternatively, when a user draws a bubble on the Sketch Board, the Partition Locator detects it and first makes a rectangular frame to fully contain the sketch bubble. Then the Partition Locator checks the relative location of the partition frame to the boundary frame, which is identified by the Boundary Locator. If the partition frame is very close to the boundary frame within a certain range then the Partition Locator will automatically attach the partition frame to the boundary frame 5. On the other hand, if the bubble is farther from the building boundary by more than a certain minimum distance, the Partition Locator will conceive the bubble as an individual room within the building. The partition frame will be placed into the interior with no attachment to the boundary frame. Figure 4.7 shows the Partition Locator recognizes several freehand bubbles and identifies them as the interior partition walls. 5 There is always ambiguity in a freehand drawing. When a designer draws a freeform bubble into a floorplan sketch and this bubble is very close to the boundary of the sketch or slightly overlaps onto the boundary, the SpaceMaker assumes the designer wants to create a room that is directly aligned with the boundary of the building.

10 47 Figure 4.7, Partition Locator recognizes several freehand bubbles and identifies them as the interior partition walls. After recognizing the partition walls, the Partition Locator will also indicate their locations by inserting guidelines on the Sketch Board. For sketch lines, there will be just one guideline corresponding to each sketch line shown on the Sketch Board (Figure 4.6); on the other hand, for sketch bubbles, several guidelines that are aligned with the boundary of the partition frame will be inserted into the sketch (Figure 4.7) Locator for Space After users complete the space layout by making freehand sketches to decide the boundary of the building and inserting partition walls into its interior, several interior spaces have already been generated by the SpaceMaker. However, other than the guidelines indicating the locations of boundary and partition walls, there are still no architectural elements shown on the Space Window. The SpaceMaker has recorded only the locations of those guidelines. The SpaceMaker will be unable to identify each individual space until the user draws symbols into the partitioned areas in the freehand sketch on the Sketch Board. When the user draws a symbol into one of the blank areas (which enclosed by guidelines and actually represent interior spaces), the Space Locator

11 identifies the space that the symbol represents. The space is identified by finding four guidelines that enclose the labeled space and recording the locations of four corners of the space. Figure 4.8 shows that how Space Locator recognizes the drawn symbol and identifies the space that the symbol represents. 48 Figure 4.8, Space Locator recognizes the drawn symbol and identifies the space that the symbol represents Operations behind Locators This section describes how the three Locators create data lists for recognizing boundaries, partitions, and spaces. When creating a smallest rectangular frame that contains the entire freehand boundary envelope, the Boundary Locator identifies four points: two end-points of the projection that the boundary frame projects onto X-axis, and the other two end-points of the projection of the boundary frame on Y-axis (Figure 4.9). The Boundary Locator then sets a List of four variables, BX-1, BX-2, BY-1, BY-2, at current values to record the building boundary.

12 49 Fig 4.9, The Boundary Locator identifies four projecting points in order to locate the boundary frame. After receiving a line input and displaying it as a horizontal or vertical straight partitioning line in the Space Window, the Partition Locator identifies the projecting point that the extension of the partitioning line intersects with X-axis or Y-axis (Figure 4.10). To record the location of partition walls, the Partition Locator then adds the projecting point (X-L or Y-L) into one of two Lists, *list-line-x* and *list-line-y*, which respectively contains projecting points of the all partitioning lines on X and Y-axis. Figure 4.10, The Partition Locator identifies the projecting points in order to locate the partition walls. Alternatively, when users use a bubble to partition the floor, the Partition Locator creates a smallest rectangular partitioning frame to contain the bubble. The Partition Locator then identifies four points: two end-points of the projection that the partitioning frame projects

13 50 onto the X-axis and the other two end-points of the projection on the Y-axis (Figure 4.11). The Partition Locator then sets two Lists, *list-bubble-x* and *list-bubble-y*, at current values (X-B-1, X-B-2, Y-B-1, Y-B-2) to respectively record those projecting points on the X and Y-axes. Figure 4.11, The Partition Locator identifies four projecting points in order to locate the partition frame. Combining all information from three Lists, the SpaceMaker creates a network system to locate each individual space inside the building boundary (Figure 4.12 (a)). When a user inserts a label in the Sketch Board, the Space Locator checks its location in relation to the network and finally identifies the labeled space (Figure 4.12 (b)). The Space Locator then identifies the four projecting points of the space frame and sets a new List, *list-space*, at current value (X-1, X-2, Y-1, Y-2) in order to record the location of the labeled space. Therefore, the coordinates of each corner of the labeled space can be identified, shown in Figure 4.12 (c).

14 51 Figure 4.12, (a) The SpaceMaker creates a network system to locate each individual space inside the building boundary. (b) The Space Locator identifies the location of the label in relation to the network and locates the labeled space. (c) The four corners of the labeled space can be identified Symbol Recognition When designers draw symbols into the sketch, not only does the Space Locator identify the location of the space that the symbol represents, but it also tries to recognize each individual symbol. By recognizing each drawing symbol, the SpaceMaker identifies the characteristic of the space that the symbol represents and then inserts appropriate architectural elements, which are pre-defined by the designers in advance (symbol definition will be addressed later in this chapter), to construct this space. Symbol recognition is handled by a Shape Recognizer that compares the similarity of each input glyph with a set of previously defined templates created by users themselves, and then the Shape Recognizer identifies the best match for the input symbol. The Shape Recognizer uses basic features of the freehand input to identify symbols containing a single stroke with simple shapes, like freeform lines with limited segments, or simple geometric polygons (rectangles or ovals). The features that the Recognizer uses are: number of corners and relative locations of starting and end points in relation to a 3x3 grid within a bounding box (the smallest rectangle to fully contain the freehand input). Corners are identified when the direction (change in heading) of line segments between raw points exceeds 60 degrees. Figure 4.13 shows the features that the Shape Recognizer uses.

15 52 Figure 4.13, The features that the Shape Recognizer uses, including number of corners and relative locations of both starting and end points in relation to a 3x3 grid Symbol Definition As described in the previous section, the Space Locator can recognize different drawing symbols and identify locations of labeled spaces. However, the SpaceMaker will still not know what to do until designers associate each symbol with a configuration of architectural elements. In order to do so, the SpaceMaker has a Symbol Definition System that enables a user to pre-define the architectural configuration associated with a symbol by assigning a set of four elements to the four sides of a space, the height of the space, and its condition of privacy. The Symbol Definition System has two pop-up windows, Symbol-Sketch Window and Symbol-Definition Window (Figure 4.14). Figure 4.14, The Symbol Definition System has two pop-up windows, (a) symbol-sketch window and (b) symbol-definition window. A designer can draw a symbol to represent a combination of spatial boundary conditions and privacy properties.

16 Users first draw a symbol to represent a certain spatial configuration. Users then can define the symbol by choosing different elements for each individual wall. The SpaceMaker offers three different types of elements that designers can choose: a solid wall (representing an element without opening), a colonnade with three columns (representing an element with relative higher degree of enclosure), and a pair of columns at two ends (representing an element without enclosure). Figure 4.15 shows three different types of elements that designers can choose for defining a symbol. In addition, the SpaceMaker allows users only two fundamental types of architectural components, walls (planar components) and columns (linear components) 6, to construct the entire building Figure 4.15, shows three different types of walls that designers can choose for defining a symbol. 6 The vertical elements, which generally include linear elements (columns) and planar elements (walls), are instrumental in defining a volume of space and providing a strong sense of enclosure for those within it. (Ching, F. 1979) 7 The reason for that is: at the early phase of designing, designers usually do not deal with specific details, like window sizes, material colors or door shapes. Instead, designers are mainly concerned with the fundamental characteristics of a space, such as the degree of enclosure, the orientation or the proportion of the space. They are also concerned with the basic relationships between all different functional spaces according to the building program. Moreover, architects make diagrams or sketches that consist of simple elements (lines or polygons) to explore alternative spatial layouts without identifying the sizes and locations of openings. Architects may also build simple massing models, which usually do not include specific details, to study the fundamental relationships of architectural spaces. So, in a digital modeling tool used in the early schematic design, the architectural components that users can choose to build up models should stick to fundamentals as well. Users assemble and arrange these two types of fundamental architectural components, planar and linear, in order to make a space contain the characteristics that they originally want to design.

17 After the designer has decided all four boundary conditions, the height, and the condition of privacy of the space, the Symbol Definition System associates that spatial configuration information with that particular freehand symbol. So, when users draw a pre-defined symbol into the sketch floor plan, the Space Locator compares the features of the symbol to previously defined symbol templates and finds the closest match. The Space Locator then retrieves the spatial configuration that this symbol represents and finally displays the space with four pre-defined wall elements in the Space Window. Figure 4.16 shows that a pre-defined symbol is inserted into the sketch, and the Space Locator recognizes the symbol and inserts the elements on the Space Window according to the architectural configuration that the symbol represents. 54 Figure 4.16, Space Locator recognizes the pre-defined symbol and inserts the elements in the Space Window according to the architectural configuration that the symbol represents.

18 Boundary Conflict 55 When a designer draws a predefined symbol into a sketch floor plan, the SpaceMaker will respond by inserting a set of four wall elements in the Space Window. However, there may be a conflict on the boundary between two adjacent spaces. That is because two sets of four wall elements will be inserted into the building when two symbols are applied to two adjacent spaces. The boundary between the two spaces will be specified by two potentially different elements. How do we decide which element should be chosen? Figure 4.17 shows the boundary conflict between two adjacent spaces. Figure 4.17, shows the boundary conflict between two adjacent spaces. The SpaceMaker has a Boundary Conflict Resolver that selects a wall element for the shared space boundary based on the privacy condition of each space to deal with the conflict. The SpaceMaker allows users to decide whether a space is to be assigned privacy priority 8. Users must make this selection when they define a symbol. The Boundary Conflict Resolver will decide which element is chosen according to the predefined settings of privacy priority. Basically, there are three rules with which the Space Locator handles the boundary conflict (Figure 4.18): 8 A space with the privacy priority simply means that the space has higher degree of enclosure to ensure the privacy of the space.

19 1. When one space has privacy priority, the SpaceMaker will always pick the element that contains less opening in order to maintain the privacy. 2. When two spaces both have privacy priority, the SpaceMaker will always pick the element that contains more opening in order to ensure circulation between two rooms. 3. When neither space has privacy priority, the SpaceMaker will also always pick the element that contains more opening in order to ensure circulation between two rooms. 56 Figure 4.18 shows the three rules that the Boundary Conflict Resolver uses to handle the boundary conflict. The reason why the SpaceMaker picks the element with more opening for cases 2 and 3 is that people may intend to allow access through the wall when they assign an element with openings (e.g., a colonnade) to this wall Modification Tools for Converted Space The SpaceMaker provides two modification tools for users, the Moving Tool and the Opening Tool 9. The Moving Tool allows users to modify the model by adjusting the 9 As discussed before, early conceptual design depends on a continuous cycling of thinking-makingthinking process. Modifications of a design idea occur repeatedly throughout the entire design process, especially during the early schematic development. The goal of the SpaceMaker is to integrate 3-D modelmaking directly into the continuous cycling of design information flow, so designers have extra information in 3-D to help refine design ideas. As a part of the cycling process, the 3-D modeling tool should also enable users to further modify models throughout the entire model-making process.

20 spatial configuration in the freehand sketch on Sketch Board. Users can move any guideline that controls the positions of boundaries between interior spaces on the Sketch Board. All rooms aligned with this picked guideline will move at the same time. By moving guidelines, designers can modify the entire configuration of space. (Figure 4.19) 57 Figure 4.19, Designers can change the entire configuration of space by moving guild-lines on the Sketch Board. The Opening Tool allows users to directly modify the model in the Space Window. Users first pick any wall in the building, either a boundary or partition wall. In the Modification Window, users can see the elevation view of this wall. Users then can either open an opening on the wall or replace the wall with a colonnade. The Opening Tool enables a designer to change the nature of any wall and thereby to change the nature of the spaces adjacent to that modified wall. Figure 4.20 shows how users change the characteristics of the partition walls by adding an opening or replacing by a colonnade.

21 58 Figure 4.20, Users can change the characteristics of the partition walls by adding an opening or switching it to a colonnade Conversion to VRML Format Enabling designers to view space in 3-D is the main purpose of the SpaceMaker. However, the way users view the space is another important issue. Virtual Reality offers an appropriate way for designers to experience the space in 3-D. Therefore, the SpaceMaker converts 2-D freehand sketches into 3-D models in VRML 3-D web format. After designers have completed a space layout by sketching, labeling, and modifying the spatial configuration, a VRML translator module outputs a standard VRML format file that any VRML enabled web-browser can read. The program assumes that the world is flat and level and that all elements will be simply extruded to a height that users have assigned while defining symbols. After creating the virtual space, users can use a VRML enabled browser to navigate and explore different viewpoints and paths, and to gain an experience of walking through the space. Figure 4.21 shows how the SpaceMaker converts a sketch into 3-D model in VRML format.

22 59 Figure 4.21, SpaceMaker converts a sketch into 3-D model in VRML format. Through a virtual experience of the space during the earliest stages of design, designers can gather spatial information for further modification. Compared to the traditional media (2-D freehand drawings or 3-D massing models), Three-dimensional-walk-throughs provide designers relatively real data for their next exploration Discussion The freehand drawing environment of the SpaceMaker maintains the flexibility of early schematic design and the ambiguity of hand-made sketching, and provides designers a

23 paper-like interface for quickly generating 3-D model by exploring 2-D spatial arrangement through freehand sketches. The implementation of the SpaceMaker has revealed that it is possible to build 3-D models in the early phases of design process by making freehand sketch floor-plans and integrating designer-defined drawing symbols into freehand sketches. Finally the SpaceMaker recognizes the fundamental features of freehand drawings and the pre-defined symbols. Designers draw to think of space; draw to explore the solution of spatial configurations; draw to make space. 60 While the SpaceMaker supports a convenient paper-like modeling environment for designers easily creating 3-D models, there are still some limitations due to the computational implementation. For example, the recognition systems currently only support single-stroke recognition. Users must complete any single task, such as enclosing a building boundary, partitioning the floor, and inserting a symbol, within only one single stroke input. In addition, the SpaceMaker currently only recognizes a built boundary with a simple rectangular shape. Any freeform envelope stroke, no matter how complex it is, is simply translated to a rectangle by the SpaceMaker. The next chapter further describes the contribution of the implementation of the SpaceMaker and discusses the limitations of the current work. Several potential directions for the future research are also discussed in the next chapter.