Abstract:
Embodiments of the present invention enable users to efficiently guide semi-automatic quantity takeoff from computer aided design (CAD) drawings by selecting multiple drawing objects and/or multiple instances of drawing objects as the target of subsequent commands. In some embodiments, the user supplements an automated portion of a quantity takeoff from a CAD drawing by selecting one or more drawing objects in a takeoff palette. The user defines the dimension (e.g., linear) to quantify and optionally the parameter to be quantified (e.g., length) for the selected drawing objects simultaneously. The quantity takeoff engine quantifies the instances associated with the selected drawing objects, performs takeoff calculations, and updates a workbook accordingly. To further facilitate the analysis of the CAD drawing, the user simultaneously selects one or more drawing objects and/or one or more instances of drawing objects to view and organize (e.g., filter, search, etc.) by properties in a properties palette.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to computer software. More specifically, the present invention relates to techniques for guiding semi-automatic quantity takeoff data from computer aided design drawings. 
     2. Description of the Related Art 
     The term computer aided design (CAD) generally refers to a broad variety of computer-based tools used by architects, engineers, and other construction and design professionals. CAD applications may be used to construct computer models representing virtually any real-world construct. Commonly, CAD applications are used to compose computer models and drawings related to construction projects. For example, a CAD application may be used to compose a three-dimensional (3D) model of a house or an office building. Once composed, these CAD models are often used to generate a variety of two-dimensional (2D) and 3D views such as plan, profile, section, and elevation views. Additionally, such models may be used to generate architectural, construction, engineering, and other documentation related to the construction project. 
     A common requirement of construction projects is to generate an estimate of the cost of the project from the building drawings. This estimate can then be used as part of the bidding process or as part of the pricing process. The term “quantity takeoff” is generally referred to as process of estimating the quantities of materials needed to construct a project based on the project drawings and specifications. The quantities involved in quantity takeoff may include numerical counts, such as the number of doors and windows in a project, but may also include other quantities such as the volume of concrete or the lineal feet of wall space. The rest of the cost estimate of a project entails determining the types of materials that will be used as well as the unit costs of those materials. 
     Today, the quantity takeoff process is typically performed manually. For example, a project manager may use a printout, a pen, and a clicker to manually count objects depicted in a set of construction documents. The project manager may physically mark each instance of an object in a CAD drawing, using the clicker to maintain an instance count. A digitizer is often used for taking measurements from the printout. The project manager or cost engineer evaluates each drawing element individually, identifies the material associated with the element, identifies and quantifies the appropriate dimension of the element, calculates the element cost, and adds the element cost to the overall cost estimate. 
     One drawback to this approach is that it has proven to be error-prone. Also, this approach is both labor intensive and time consuming. Moreover, if the project design is modified after the original cost estimate is calculated, the takeoff process may need to be repeated. If the takeoff process is not repeated after design changes, accumulated inaccuracies in the cost estimate may adversely affect the bidding or pricing process. Another drawback to the manual approach is that it is difficult and expensive to accurately assess the cost impact of different design choices. 
     As the foregoing illustrates, what is needed is a more effective and flexible technique for estimating the cost of a construction project and, more particularly, for generating quantity takeoff data. 
     SUMMARY OF THE INVENTION 
     One embodiment of the present invention sets forth a method for performing quantity takeoff computations. The method includes the steps of receiving a selection of a drawing object, where at least one instance of the selected drawing object is included in a computer-aided design (CAD) drawing, determining a takeoff object associated with the selected drawing object, generating a quantified value for each instance of the selected drawing object based on a takeoff property associated with the takeoff object, and computing a cost estimate for each instance of the selected drawing object based on the quantified value for the instance and cost data included in the takeoff object. 
     One advantage of the disclosed method is that, by enabling the user to select multiple drawing objects and/or instances of drawing objects and subsequently apply commands to all of the selections simultaneously, the quantity takeoff engine and the graphical user interface streamline the takeoff design process. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
         FIG. 1  is a conceptual diagram of a computer system in which one or more aspects of the invention may be implemented; 
         FIG. 2  is a conceptual diagram of elements of the system database of  FIG. 1 , according to one embodiment of the invention; 
         FIG. 3  is a conceptual diagram of a 2D sheet, according to one embodiment of the invention; 
         FIG. 4  illustrates an exemplary takeoff palette of  FIG. 1 , according to one embodiment of the invention; 
         FIG. 5  illustrates an exemplary properties palette of  FIG. 1 , according to one embodiment of the invention; 
         FIGS. 6A and 6B  are a flow diagram of method steps for generating a takeoff report, according to one embodiment of the invention; and 
         FIG. 7  is a flow diagram of method steps for displaying properties associated with instances of the drawing objects, according to one embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a conceptual illustration of a computer system  100  in which embodiments of the invention may be implemented. As shown, the computer system  100  is configured to store takeoff data, perform takeoff measurements, generate takeoff reports, and display design and takeoff properties. In one embodiment, the components illustrated in computer system  100  include computer software applications executing on existing computer systems, e.g., desktop computers, server computers, laptop computers, tablet computers, and the like. The software applications described herein, however, are not limited to any particular computing system and may be adapted to take advantage of new computing systems as they become available. 
     Additionally, the components illustrated in computer system  100  may be software applications executing on distributed systems communicating over computer networks including local area networks or large, wide area networks, such as the Internet. For example, a graphical user interface  104  may include a software program executing on a client computer system communicating with a quantity takeoff engine  102 . Also, in one embodiment, the quantity takeoff engine  102  and the graphical user interface  104  may be provided as an application program (or programs) stored on computer readable media such as a CD-ROM, DVD-ROM, flash memory module, or other tangible storage media. 
     As shown, the computer system  100  includes, without limitation, the quantity takeoff engine  102 , the graphical user interface  104 , a keyboard  112 , a mouse  114 , a display device  116 , a processor (not illustrated), a system database  106 , a project database  108 , and a CAD drawing  110 . The quantity takeoff engine  102  may be configured to allow users interacting with the graphical user interface  104  via the keyboard  112  and the mouse  114  to generate takeoff objects containing properties (i.e., information) used to perform the quantity takeoff, such as the unit cost of construction materials, and takeoff reports detailing the estimated cost of the project. 
     In one embodiment, the system database  106  may include information, such as drawing information and the unit cost of labor, shared among multiple CAD projects. Further, the system database  106  may include object type history and mapping preferences that may be used by the quantity takeoff engine  102  to assign takeoff properties to the takeoff objects. The object type history records takeoff information used in previous CAD projects and the mapping preferences specify defaults values for takeoff properties. Typically, the mapping preferences will vary depending on the project type (i.e., the type and format of information available in the CAD drawing  110 ). Similarly, the project database  108  may also include drawing information and takeoff calculations, but it may also include project-specific data, such as project cost. 
     The composition of a given design project may be reflected in a collection of one or more CAD drawings  110 . Illustratively, CAD drawing  110  includes a three-dimensional (3D) model  122  and one or more two-dimensional (2D) sheets  124 . The 3D model  122  may represent virtually any real-world construct, for example, a construction plan for a building. In such a case, the 3D model  122  may include detailed 3D geometry representing the building, each floor of the building, and different systems for the building (e.g., electrical systems, HVAC systems, etc.). The 2D sheets  124  may be derived from the 3D model  122  and provide different views of the 3D model  122 , such as plan, profile, and section views of the project. In one embodiment, the quantity takeoff engine  102  may be configured to use and generate information in the system database  106 , the project database  108 , and the CAD drawing  110 . Accordingly, the quantity take off engine  102  and the graphical user interface  104  may include programmed routines or instructions allowing users to create, edit, load, and save elements from system database  106 , the project database  108 , and/or the CAD drawing  110 . In the context of the present invention, for example, the graphical user interface  104  may allow users to create, edit, load, select, and save takeoff objects and takeoff reports. Those skilled in the art will recognize, however, that the components shown in  FIG. 1  are simplified to highlight aspects of the present invention and that the graphical user interface  104  may include a broad variety of additional tools and features used to compose and manage the system database  106 , the project database  108 , and the CAD drawing  110 . 
       FIG. 2  is a conceptual illustration of elements in the system database  106  of  FIG. 1 , according to one embodiment of the invention. As shown, the system database  106  includes a drawing category  200  and a takeoff category  202 . The drawing category  200  and the takeoff category  202  are used to organize data within the system database  106 . Those skilled in the art will recognize, however, that the components shown in  FIG. 2  are simplified to highlight aspects of the present invention and that the system database  106  may include a wide variety of organizational structures and data. 
     As shown, the drawing category  200  includes a drawing object  1   204 , a drawing object  2   206 , a drawing object N−1  208 , and a drawing object N  210 . Each of the drawing objects  204 ,  206 ,  208 , and  210  may be created, edited, and used by various CAD tools, including the quantity takeoff engine  102  and the graphical user interface  104  of  FIG. 1 . Furthermore, each of the drawing objects  204 ,  206 ,  208 , and  210  may define an abstract template from which specific instances, or entities, may be created. For example, the drawing object  1   200  may define a toilet object and the CAD drawing  110  of  FIG. 1  may contain numerous instances of toilets, each of which inherits some data from the toilet object designated by drawing object  1   200 . This hierarchy simplifies changes and ensures consistency throughout a construction project. 
     Illustratively, the drawing object  1   200  includes a globally unique identifier (GUID)  220 , linework  222 , and properties  224 . The GUID  220  uniquely identifies the drawing object  1   200  to the quantity takeoff engine  102 , the graphical interface  104 , and any other associated CAD tools in the computer system  100  of  FIG. 1 . That is GUID  220  may be used to represent a common class of drawing objects in CAD drawing  110 . Furthermore, GUID values may be used by other constructs, such as takeoff objects and instances of drawing object  1   200 . The linework  222  may define shapes, such as points, lines, and curves that may be displayed by the graphical user interface  104 . For example, the linework  222  could provide the shapes required to display a toilet in 3D views or in 2D profile, plan, or section views generated from the CAD drawing  110 . The properties  224  may further define how CAD tools interact with the object  1   200  and any instances of object  1   200 . The properties  224  may define metadata about a given drawing object such as width, height, weight, etc. Each of the drawing objects  206 ,  208 , and  210  may include similar information, representing different objects that may be included in the CAD drawing  110 . 
     The takeoff category  202  includes a takeoff object  1   212 , a takeoff object  2   214 , a takeoff object N−1  216 , and a takeoff object N  218 . The takeoff category  202  may correspond to a standard organizational system, such as CSI-16 or Uniformat. The takeoff category  202  may be used by the takeoff reporting tools  120  to organize the information in the takeoff report. Each of the takeoff objects  212 ,  214 ,  216 , and  218  may correspond to a drawing object, such as drawing object  1   200 , and may be created, edited, and used by various CAD tools, including the quantity takeoff engine  102  and the graphical user interface  104 . For example, a takeoff object, such as takeoff object  1   212 , corresponding to a toilet drawing object may be created, added to the takeoff category  202  for plumbing fixtures, and subsequently used for quantity takeoff. 
     As shown, the takeoff object  1   212  includes one or more corresponding GUIDs  226 , a quantify type  228 , a quantify property  230 , and cost data  232 . During a quantity takeoff process, the drawing object GUID  226  may be used to identify a particular drawing object and a corresponding set of instances to which the data in takeoff object  1   212  may be applied. The quantify type  228 , the quantify property  230 , and the cost data  232  may then be used to estimate the cost of each of the instances associated with the takeoff object  1   212 . In one embodiment, the quantify type  228  defines the type of enumeration, such as count, linear, volume, or area, that is used to calculate the cost of each instance. And the quantify property  230  may define an instance-specific property, such as a length or a volume, corresponding to the quantify type  228 . In other words, the quantify property  230  defines how the cost of a collection of instances of a given drawing element should be quantified for a takeoff report. The cost data  232  may include numerical constants, such as labor cost per unit, as well as takeoff equations used to estimate cost. 
     For example, the takeoff object  1   212  may be created to correspond to the drawing object of a toilet. In this example, the drawing object GUID  226  of the takeoff object  1   212  may be identical to the object GUID  220  of the drawing object corresponding to the toilet, thereby indicating that the information in the takeoff object  1   212  may be applied to all instances of the drawing object (i.e., instances of the toilet) in a given CAD drawing  110 . In this case, the quantify type  228  may be set to count, indicating that the quantity to measure during takeoff is simply the number of instances of the drawing object corresponding to the toilet. Furthermore, the cost per toilet may be specified in the cost data  232 . The information in takeoff object  1   212 , when applied to the CAD drawing  1110 , allows all instances of the toilet in CAD drawing  1   110  to be counted and the total cost of the toilets to be added to the total cost for the project represented by CAD drawing  1   110 . 
     In alternate embodiments, each of the takeoff objects may correspond to one or more drawing objects and/or one or more instances of drawing objects. Again, the takeoff object may be created, edited, and used by various CAD tools, including the quantity takeoff engine and the graphical user interface. The granularity at which the CAD tools apply the information in the takeoff object may be determined by whether the CAD tools is applying the information in the takeoff object to a corresponding drawing object or an instance of a drawing object. The drawing object GUID may be supplemented or subsumed by a list of GUIDs which establish the correspondence between the takeoff object and the drawing object(s) and/or instances of drawing object(s). 
       FIG. 3  illustrates an example of one of the 2D sheets  124  of  FIG. 1 , according to one embodiment of the invention. As shown, the 2D sheet  124  includes an instance  1   300  of a drawing object, an instance  2   302  of a drawing object, an instance N−1  304  of a drawing object, and an instance N  306  of a drawing object. Each of the instances  300 ,  302 ,  304 , and  306  corresponds to a drawing object, such as drawing object  1   204  of  FIG. 2 . Each drawing object may be defined in the system database  106  of  FIG. 1 , the project database  108  of  FIG. 1 , or the CAD drawing  110  of  FIG. 1 . 
     The instance  1   300  is configured to include a drawing object GUID  308 , a position  310 , an instance GUID  312 , and properties  314 . The instance  1   300  may inherit data from the drawing object designated by the drawing object GUID  308 . For example, if the drawing object corresponding to the drawing object GUID  308  defines a door, instance  1   300  will inherit the linework  222  and the properties  224  that define this door. The position  310  specifies the location of the instance  1   300  relative to other instances, such as the instance N  306 , included in the CAD drawing  110 . For example, the position  310  may specify a 3D coordinate location within a space represented by the 2D sheet  124 . The instance GUID  312  uniquely identifies the instance  1   300  to the quantity takeoff engine  102 , the graphical interface  104 , and any other associated CAD tools in the computer system  100  of  FIG. 1 . While instance  1   300  and instance  2   302  may share the same drawing object GUID  308 , thereby indicating that they are both instances of the same drawing object, instance  1   300  and instance  2   302  have different instance GUIDs  712 . The properties  314  include information that is specific to each instance, as opposed to information that is shared between instances of the same object. For example, one of the properties  314  such as length or width may be used as the basis for quantifying the instance  1   300  during a quantity takeoff process. Each of the instances  302 ,  305 , and  306  may include similar information. 
       FIG. 4  illustrates an exemplary takeoff palette  182  of  FIG. 1 , according to one embodiment of the invention. The takeoff palette  182  may be configured to allow the user to enter and to view the quantify type  228  and the quantify property  230  included in each of the takeoff objects  212 ,  214 ,  216 , and  218  of  FIG. 2 , corresponding to the drawing objects  204 ,  206 ,  208 , and  210 , respectively. 
     As shown, under the “description” heading, the takeoff palette  182  includes drawing categories  200 , such as a walls category. Within each drawing category  200 , the takeoff palette  182  includes drawing objects, such as drawing objects representing various types of exterior and interior walls. Again, each drawing object corresponds to one takeoff object. Further, for each drawing object, adjacent to the drawing object description, the takeoff palette  182  displays the quantify type  228  (shown, for example, under the “type” heading) and the quantify property  230  (shown, for example, under the “map” heading) included in the takeoff object corresponding to the drawing object. The takeoff palette  182  may also be configured to display the instances of each of the drawing objects (not shown). 
     The quantity takeoff engine  102  is configured to populate the takeoff palette  182  using takeoff objects, object type history and mapping preferences included in the system database  106 . During an automated quantity takeoff process, the quantity takeoff engine  102  attempts to map drawing objects to takeoff objects included in the system database  106 . The quantity takeoff engine  102  may search for takeoff objects that correspond to drawing objects in any technically feasible fashion. For example, the quantity takeoff engine may read an object GUID included in a particular drawing object and search for a takeoff object that includes a matching drawing object GUI. For each drawing object that does not map to an existing takeoff object, the quantity takeoff engine  102  creates a takeoff object and applies the object type history and the mapping preferences. The object type history includes the names of drawing objects and corresponding quantify types specified in previous CAD projects. The quantity takeoff engine  102  attempts to pattern match the names of the drawing objects to the names of the drawing objects in the object type history. After finding a match, the quantify takeoff engine  102  assigns the corresponding quantify type included in the object type history to the quantify type  228  included in the takeoff object corresponding to the drawing object. Similarly, the quantity takeoff engine  102  uses the mapping preferences to assign a default quantify property  230  based on the quantify type  228 . More specifically, if a quantify type  228  is specified but a quantify property  230  is not specified, then the quantity takeoff engine  102  assigns a default quantify property  230  based on the quantify type  228 . 
     The takeoff palette  182  enables the user to select multiple drawing objects simultaneously, such as selected drawing objects  406 , and apply a single specification to all of the takeoff objects corresponding to the selected drawing objects. In this example, the selected drawing objects  406  includes seven exterior wall drawing objects corresponding to seven takeoff objects. A user-specified quantify type selection  402  configures the quantity takeoff engine  102  to assign the specified value to the quantify types  228  included in the takeoff objects corresponding to the selected drawing objects  406 . Further, the quantity takeoff engine  102  uses the mapping preferences to identify a default quantify property value based on the specified quantify type. The quantity takeoff engine  102  then assigns this default quantify property value to the quantify properties  230  included in the takeoff objects corresponding to the selected drawing objects  406 . Finally, the quantify takeoff engine  102  quantifies all instances of the selected drawing objects  406 , estimates costs for these quantified instances, and updates a workbook to reflect the estimated costs. In this example, the quantify type  228  may be one of undefined, linear, area, volume, or count. Illustratively, linear is selected and, therefore, the quantity takeoff engine  102  assigns linear to the quantify types  228  included in the seven takeoff objects corresponding to the selected drawing objects  406 . Subsequently, the quantity takeoff engine  102  updates the quantify property  230 , quantifies the instances of the selected drawing objects  406 , estimates the costs, and updates the workbook accordingly. 
     The user may also specify a quantify property selection  404 . The quantify property selection  404  configures the quantity takeoff engine  102  to assign the specified value to the quantify properties  230  included in the takeoff objects corresponding to the selected drawing objects  406 . The quantify takeoff engine  102  then quantifies all instances of the selected drawing objects  406 , estimates costs for these quantified instances, and updates the workbook to reflect the estimated costs. To facilitate the specification of the quantify property  230 , the quantity takeoff engine  102  configures the takeoff palette  182  to present a list of instance-specific properties that may be quantified using the current quantify type  228 . In this example, the quantify property  230  may be one of base offset, length, top offset, unconnected height, or width. Illustratively, length is selected, consequently, when the quantity takeoff engine  102  performs quantity takeoff on the selected drawing objects  406 , the length property of the instances of the selected drawing objects  406  are the basis of a cost estimate. 
       FIG. 5  illustrates an exemplary properties palette  184  of  FIG. 1 , according to one embodiment of the invention. The properties palette  184  is configured to allow the user to view, manipulate (e.g., sort, filter, etc.), and select one or more instances of one or more drawing objects. As shown, the properties palette  184  includes two selectable tabs: design and takeoff. Illustratively, the design tab is selected. If the design tab is selected, then the properties palette  184  displays instance-specific values of design properties, such as length. Similarly, if the takeoff tab is selected, then the properties palette  184  displays instance-specific values of takeoff properties, such as cost. In alternate embodiments, the properties palette may be configured to display instances of drawing objects and/or drawing objects. 
     The properties palette  184  enables the user to select one or more instances of one or more drawing objects simultaneously. Further, the graphical user interface  104  configures the properties palette  184  and the takeoff palette  182  to work together. More specifically, after selecting one or more drawing objects and/or one or more instance of drawing objects using the takeoff palette  182 , the graphical user interface  104  populates the properties palette  184  with all of the instances of the selected drawing objects and the selected instances of drawing objects. Similarly, the user may select one or more instances of drawing objects, not shown, using the properties palette  184 , and the graphical user interface  104  automatically selects the same instances of drawing objects in the takeoff palette  182 . Further, the user may select one or more instances of one or more drawing objects in the properties palette  184  and create a new drawing object and associated takeoff object that represent all of the selected instances. Both the takeoff palette  182  and the properties palette  184  support selection of non-homogeneous instances. In other words, the user may select one or more instances of different drawing objects and/or one or more drawing objects belonging to different drawing categories. Further, the user may select instances of drawing objects, drawing objects, or any combination thereof. 
     The properties palette  184  includes a variety of tools that facilitate the viewing, filtering, and sorting of design properties and takeoff properties associated with the instances of the drawing objects. Selecting, viewing, filtering, and sorting this information facilitates efficient analysis of the CAD drawing  110 . Illustratively, a selected sorting property  502  is specified as a top constraint property. Consequently, the graphics user interface  104  sorts the instances displayed in the properties palette  184  according to the instance-specific top constraint property. Further, the user may select one of more of the instances and create a new drawing object and corresponding takeoff object that represent the selected instances. For example, the user may select the eleven instances with a top constraint property of “T. O. Entry Parapet” and, subsequently, create a new drawing object and corresponding takeoff object that represent these eleven instances. 
     Those skilled in the art will recognize that the components shown in  FIG. 5  are simplified to highlight aspects of the present invention and that the properties palette  184  may include a broad variety of additional tools and features used to compose and manage the drawing objects and the instances of the drawing objects included in the CAD drawing  110 . 
       FIGS. 6A and 6B  is a flow diagram of method steps for generating a takeoff report, according to one embodiment of the invention. Although the method  600  is described in conjunction with the systems of  FIGS. 1-5 , persons skilled in the art will understand that any system that performs the steps of the method  600 , in any order, is within the scope of the invention. 
     As shown, the method  600  begins at step  602 , where the quantity takeoff engine  102  is involved, the CAD drawing  110  is loaded, the system database  106  is loaded, and automated quantity takeoff is launched. At step  604 , the quantity takeoff engine  102  attempts to map drawing objects to takeoff objects included in the system database  106 . The quantity takeoff engine  102  may search for takeoff objects that correspond to drawing objects in any technically feasible fashion. For example, the quantity takeoff engine may read an object GUID included in a particular drawing object and search for a takeoff object that includes a matching drawing object GUI. Alternatively, the quantity takeoff engine may use pattern matching based on the name of the drawing object to select a corresponding takeoff object. 
     At step  606 , the quantity takeoff engine  102  populates the takeoff palette  182  with the drawing objects and the instances of the drawing objects included in the CAD drawing  110 . As part of step  606 , the quantity takeoff engine  102  creates takeoff objects corresponding to drawing objects that are not mapped to previously defined takeoff objects. Further, the quantity takeoff engine  102  uses the object type history and the mapping preferences included in the system database  106  to assign the quantify type  228  and the quantify property  230  to these takeoff objects. If the quantity takeoff engine  102  does not identify a previous or default value for the quantify type  228  and/or the quantify property  230  corresponding to a particular drawing object, then the quantity takeoff engine  102  sets the quantify type  228  and/or the quantify property  230  included in the corresponding takeoff object to undefined. 
     At step  608 , the quantity takeoff engine  102  quantifies all instances of drawing objects that include a defined quantify type  228  and a defined quantify property  230 . More specifically, for each drawing object, the quantity takeoff engine  102  uses the quantify type  228 , the quantify property  230 , and any additional measurement calculations included in the corresponding takeoff object, in conjunction with the instance-specific values of the quantify property  230 , to quantify the instances of the drawing object. For example, the quantity takeoff engine may quantify a dry wall instance by dividing a specified wall length property by a constant linear length representing the length of a dry wall panel to determine a count of dry wall panels. At step  610 , the quantity takeoff engine  102  uses the cost data  232  included in the takeoff objects to calculate an estimated cost for all of the quantified instances in the CAD drawing  110 . Subsequently, the quantity takeoff engine  102  generates a takeoff report that includes these estimated costs. 
     At step  612 , the user selects one or more drawing objects using the takeoff palette. At step  614 , the user specifies a quantify type  228  or a quantify property  240 . The quantity takeoff engine  102  applies the specified quantify type  228  or quantify value  230  to the takeoff objects corresponding to the selected drawing objects. As part of step  612 , if the user specifies a quantify type  228 , then the quantity takeoff engine  102  uses the mapping preferences included in the system database  106  to assign a default quantity property  230  based on the specified quantify type  228  to the takeoff objects corresponding to the selected drawing objects. 
     At step  616 , the quantity takeoff engine  102  quantifies all instances of the selected drawing objects. At step  618 , the quantity takeoff engine  102  uses the cost data  232  included in the takeoff objects to calculate an estimated cost for all instances of the selected drawing objects. Subsequently, the quantity takeoff engine  102  updates a workbook to reflect these estimated costs. At step  620 , if the graphical user interface  104  determines that the user makes a new selection of one or more drawing objects using the takeoff palette  182 , then the method  600  returns to step  614 , where the user specifies a quantify type  228  or a quantify property  230 . The method  600  proceeds in this fashion, looping through steps  614 - 620 , until the user does not select any instances. The method  600  then terminates. 
       FIG. 7  is a flow diagram of method steps for displaying properties associated with instances of the drawing objects. Although the method  700  is described in conjunction with the systems of  FIGS. 1-5 , persons skilled in the art will understand that any system that performs the steps of the method  700 , in any order, is within the scope of the invention. 
     As shown, the method  700  begins at step  702 , where the quantity takeoff engine  102  is involved, the CAD drawing  110  is loaded, the system database  106  is loaded, and automated quantity takeoff is launched. At step  704 , the quantity takeoff engine  102  populates the takeoff palette  182  with the drawing objects and the instances of the drawing objects included in the CAD drawing  110 . Further, the quantity takeoff engine  102  quantifies instances of drawing objects, estimates costs, and generates the workbook. At step  706 , the user selects one or more drawing objects and/or one or more instances of drawing objects using the takeoff palette  182 . At step  708 , the user requests that the graphical user interface  104  populate the properties palette  184 . At step  710 , the graphical user interface  104  displays the properties of the selected instances and all instances of the selected drawing objects using the properties palette  184 . The displayed properties may include instance-specific design properties (e.g., length), instance-specific takeoff properties (e.g., cost), or any combination thereof. At step  712 , the graphical user interface  104  organizes, sorts, and re-displays the selected instances in the properties palette  184  based on user-selections. For example, the user may configure the properties palette to sort the selected instances according to the values of the instance-specific length property. At step  714 , if the graphical user interface  104  determines that the user makes a new selection of one or more drawing objects using the takeoff palette  182 , then the method  700  returns to step  708 , where the user requests that the graphical user interface  104  populate the properties palette. The method  700  proceeds in this fashion, looping through steps  708 - 714 , until the user does not select any instances. The method  700  then terminates. 
     In sum, the takeoff process used to generate estimated costs for a construction process is facilitated by enabling the simultaneous selection and access of multiple drawing objects and/or instances of drawing objects in a CAD drawing. In some embodiments, the user first executes an automated quantity takeoff. During the automated quantity takeoff, the quantity takeoff engine maps instances of drawing objects to takeoff objects that are defined in the system database, quantifies the instances associated with the defined takeoff objects, performs takeoff calculations, and generates a workbook. Also during the automated quantity takeoff, the quantity takeoff engine populates a takeoff palette. After the automated quantity takeoff is completed, the user may select one or more drawing objects from the takeoff palette and simultaneously modify the quantify type (e.g., count, linear, area, etc.) and/or quantify property (e.g. length). If the user does not define a quantify property, then the quantity takeoff engine will assign a default quantify property based on a properties mapping included in the system database. Subsequently, the quantify takeoff engine automatically quantifies the instances associated with the selected drawing objects, performs takeoff calculations, and updates the takeoff report. In addition to viewing the data in the takeoff report, the user may analyze the CAD drawing using a properties palette. The user simultaneously selects one or more drawing objects and/or one or more instances of drawing objects from the takeoff palette. The graphical user interface then displays and allows the user to organize (e.g., filter, search, etc.) the design properties and the takeoff properties associated with the selections in the properties palette. 
     Advantageously, by enabling the user to select multiple drawing objects and/or instances of drawing objects and subsequently apply commands to all of the selections simultaneously, the quantity takeoff engine and the graphical user interface streamline the takeoff design process. Furthermore, automatically performing takeoff on the instances associated with selected drawing objects reduces the time required to perform takeoff measurements and facilitates an incremental, interactive design approach that is favored by some users. Finally, by enabling the user to intelligently select, display, and organize instances of drawing objects using the properties palette, the graphical user interface facilitates quickly and accurately assessing the impact of different design choices 
     While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. For example, aspects of the present invention may be implemented in hardware or software or in a combination of hardware and software. One embodiment of the invention may be implemented as a program product for use with a computer system. The program(s) of the program product define functions of the embodiments (including the methods described herein) and can be contained on a variety of computer-readable storage media. Illustrative computer-readable storage media include, but are not limited to: (i) non-writable storage media (e.g., read-only memory devices within a computer such as CD-ROM disks readable by a CD-ROM drive, flash memory, ROM chips or any type of solid-state non-volatile semiconductor memory) on which information is permanently stored; and (ii) writable storage media (e.g., floppy disks within a diskette drive or hard-disk drive or any type of solid-state random-access semiconductor memory) on which alterable information is stored. Such computer-readable storage media, when carrying computer-readable instructions that direct the functions of the present invention, are embodiments of the present invention. Therefore, the scope of the present invention is determined by the claims that follow.