The ability to read and interpret technical drawings is important in a large number of trades and professions, from bricklaying to engineering. Essentially, two skills are required: to understand the meaning of the lines and symbols drawn on the page; and to make the mental conversion of these two dimensional drawings (plans and elevations) into a three dimensional (3-D) reality, ie. spatial reasoning skills. Modern computing software offers a powerful medium for assisting the student to build up spatial reasoning skills in understanding technical drawings. This paper describes a computer based learning package under development, which utilises the interactive multimedia capabilities of the Apple Macintosh computer in several innovative ways. The structure of the program is discussed, as are some planing and design issues . The paper concludes with a description of some innovative applications of interactive multimedia which are used in the program. It is envisaged that the package will have application in the TAFE and secondary education sectors, as well as for off the job training in building related industries.
The situation becomes more complex when trying to explain the motion and relationships of three dimensional (3D) objects. It is very difficult to describe the motion of conceptual objects, such as the vibration of a molecule, by traditional methods. When dealing with real objects, such as the human body, video footage may be used, but this is shown sequentially and students may only play it in a predefined way.
Computers are very well suited to conveying 3D representations of objects. Because of this they can be used to assist the student to develop spatial reasoning skills much more effectively than traditional methods. While the computer screen is two dimensional, software can be used to produce exact perspective views. Rendering techniques can be used to make objects appear three dimensional, and objects can be rotated at will. Animation techniques can be used to incorporate movement. Animations can be stored as digital video, using Apple Computer's QuickTime technology and manipulated by the student to create a virtual reality environment.
In the past this skill has not been taught; rather it has been picked up in a process of osmosis by working in the trade. It is true that technical drawing and, more recently, Computer Assisted Draughting (CAD) is taught to apprentices at TAFE, but this focuses on techniques of drawing, not on how to interpret existing drawings.
Some people have inherently good spatial perception skills, and find it easy to visualise three dimensions from drawings. Teachers in the manual arts are likely to fall into this category. However, many people do not have native skills in this area, and they need to learn them. This may be difficult for their teachers to appreciate.
The project described here uses interactive multimedia (IMM) computer based learning (CBL) techniques to assist the student to build up their own three dimensional reasoning skills in understanding technical drawings. The resultant CBL program encourages the student to interact with it wherever possible by using questions and hotwords as a branching mechanism. In some cases, the student manipulates three dimensional objects with virtual reality techniques.
Because it is a self paced tutorial, students with good visualisation skills can cover the material quickly, while those without the skills can take as long as they like.
It is important to realise that the program described here is a fairly advanced prototype, which still requires many hours of work to reach completion. Funding is currently being sought to speed the development.
SuperCard is event driven. Each event, such as a mouse action, is passed as a message through a hierarchy of objects. Messages are first trapped by buttons, fields or graphics, if there is no handler for this message in that object, then the message is passed to the card, then the background, window and project, in that order. It is a very flexible programming environment, which can be used with varying degrees of efficiency. It contains some fairly powerful text and graphics editing functions. Sound and graphics may be imported, as can digital video.
Entry level training... should focus on providing new entrants to the workforce with skills in areas including: Plan reading and interpreting specifications... reading, interpreting plans and specifications are essential to the process of workplace reform.However, two other factors influenced my involvement with the project. The first of these was a contact made with a semi-retired builder, Peter Waller, who has many years experience in the building trade. He had realised many years ago that there was a gap in learning in understanding technical drawings, and had in fact presented a course on this topic at TAFE in the late Seventies, but then left the city and the course lapsed. Peter's knowledge in building drawings and the trade complemented my interest in using IMM in spatial cognition and led to a fruitful partnership. Peter is largely responsible for the content of this program, while I have provided the programming and design.
The second reason for taking on this development was that one of the major roles of my current position is managing IMM projects at Curtin in which other academics are involved with Computing Centre staff (Phillips, 1993). By working on my own project, I could become aware first hand of the sort of problems arising in Interactive Multimedia development. I could make the same mistakes as the other academics in coping with this new medium. In this way I could know better how to resolve problems as they arose, and thus expedite development of a number of projects.
The current project deviates in several key areas from these 'best practices'. The major reasons for this are that the project has had minimal funding, and the work has been done as my personal research work, which, given my position in the Computing Centre, has meant it has been done on evenings and weekends.
The limited research funds which I had available were used to employ people to create some CAD drawings, and do some computer modelling and rendering. Latterly, I have also paid for some advice on graphic design.
Current practice would say that as much as possible of a project should be designed on paper before touching the computer, and this was not the case here. This project, as with many of our earlier efforts, evolved through a series of prototypes. The major reason for this was inexperience. I was unfamiliar with the programming environment, and Peter had little experience in converting his accumulated knowledge into course material. Both Peter and I were unfamiliar with expressing the material in a form suitable for IMM, despite having many ideas. In some ways, the material in Understanding Technical Drawings was more difficult to design because there was no existing course material in this area.
In common with many IMM projects, it seemed small when it started, but it continually grew until it became unwieldy. There is always a tendency for this to happen as one defines the course material in detail. As a consequence of this growth tendency, the scope of the program was reduced to focus only on building drawings. Subsequent versions of the work can easily be extended to engineering drawings, electrical diagrams and boat building, among other areas.
The topic of Understanding Technical Drawings is inherently pictorial. However, we followed the traditional academic way of preparing course material. That is, we developed the lesson content from a textual viewpoint, thinking to find appropriate graphics later. We discovered later that it would have been far more efficient for this topic to have chosen the graphics and fitted the lesson to the pictures. In this work, the picture is the message and the words provide the necessary explanation. Had we realised this, we could have saved lots of wasted work.
The problems discussed in the preceding paragraphs have certainly slowed down the development of this package. The screen design and navigational structure have each gone through several incarnations. However, it is hoped that this has not affected the quality or applicability of the product as it stands now. In fact the lessons learnt in this and other projects have led us to develop structures and procedures for future CBL projects, with the aim of making development more efficient, while keeping the quality (Phillips, 1993).
Much of the work of development in IMM is very repetitive. One tends to repeat similar elements or objects on many screens with similar properties and programming (Phillips, 1994). The Understanding Technical Drawings project introduces several labour saving techniques to speed up the repetitive aspects of development, as discussed later.
Figure 1: The general hierarchical structure of information in the program.
The program is organised into chapters, topics and subtopics. There are four chapters: Introduction, Visualisation, Building Drawings and Components. Space has been reserved for a fifth chapter showing more complex examples. Table 1 shows the names of all the topics and subtopics.
|Chapter 3||BUILDING DRAWINGS|
Chapter 1 is the shortest. It contains introductory information about how to use the program, who and what it is for, and who was involved with it. It also sets out the learning objectives.
Chapter 2 deals with visualising three dimensional information. The basics of dimensions are covered, as well as what technical drawings are. A second topic looks at the conversion from two to three dimensions with several examples. A further topic looks at the same examples, but now there are hidden parts which are not obvious from the standard views of an object. Chapters 1 and 2 are common to the understanding of any type of technical drawing.
Chapter 3 focuses specifically on building drawings, considering first sets of drawings and then the site plan. A third topic looks at the various parts of a building drawing, ie. plans, elevations, sections, etc. A fourth topic covers specialised types of building drawings.
Chapter 4 is the reference chapter, dealing with the components of building drawings. It contains descriptions of the terminology and symbols used in building drawings, as well as sections on scales and measurements. Some of this material may be reached by hotword links from Chapter 3. When the user clicks on a hotword they are taken to the appropriate part of the reference section for a detailed explanation. In some IMM programs, the user is able to continue browsing from the point they reached by the hotword. A danger of this approach is that the user can become lost in hyperspace (Smith, 1989). To prevent this we decided that a user who reaches the reference section by means of a hotword must return directly to the topic he or she came from.
Figure 2: The main menu screen
Within each subtopic, the user moves from screen to screen using the Control Box shown in Fig. 3. The arrows move forwards and backwards through the screens in a given topic. On the first screen of a sequence, the back arrow takes the user back to the relevant menu screen. This also happens with the forward arrow on the last screen of a sequence. The button at the bottom left of the Control Box always takes the user back to the previous menu screen. The name of this button changes from Contents to Chapter to Topic to Subtopic to indicate which level of the hierarchy the user wants to go back to.
Figure 3: The navigation control box
All other functions of the program are encompassed within the Options button. Pressing on this button activates a popup menu containing a list of items which the user may want to use occasionally. This strategy was chosen to simplify the user interface for novice users. The novice user only has to choose topics from the menu and move through these topics with the arrows. However, there are other features which are built into the program which may be of interest to more sophisticated users. Currently the Options popup menu contains three items: Map, Main Contents and Quit. As the project evolves, more functions may be required. These can be built into the Options popup menu without affecting the screen design and layout.
However, a third method of navigation has been provided under the Options popup menu. This is a dynamic map of the program, showing where the user is at any given time. The five chapters currently contain 603 screens which are divided into seventeen topics and forty three subtopics. It is impossible to display all of these at once on one screen, so it was necessary to develop a map scheme which only shows the details of where the user currently is in hyperspace (see Figure 4). This idea was adapted from the work of Bearman (1992).
Figure 4: An example of the dynamic map
The dynamic map always shows the chapter and topics. As a topic is selected by a mouse click, a list of its subtopics are shown, and if a subtopic is chosen from the list then a list of the screens (cards) in that subtopic is shown. If a topic does not have any subtopics, then the list of screens in that topic is shown immediately. The user can therefore browse through the topics, subtopics and screens, and can go directly to any card simply by double clicking on the name in the list. Each chapter is colour coded, and the map reflects the colour of the chapter the user is in. The current card, subtopic, topic and chapter is highlighted in the map, if appropriate.
Stringer (Stringer, 1992) simulated the use of the microscope by capturing video through a microscope while the focus was being adjusted. The resulting QuickTime movie was manipulated with an appropriate control to simulate the focussing process. Stringer also developed a technique of filming a small object, such as a model of a building, rotating on a turntable. This generates a loop of film (see Fig. 5). Using a slider control (see Fig. 6), it is possible to rotate this object to see it from any side.
Figure 5: A loop of film taken of a rotating object
Figure 6: The slider technique to look at an object from any side
The Apple Computer Advanced Technology Group developed the "Navigable Scenes" technique (Yawitz, 1993), where a security camera is used to film the interior of a room or space from all angles. The user can look around in this room in any way they wish.
The author has combined these latter techniques using a computer generated model instead of video. Initially, these animations were created on the Apple Macintosh. When it became clear that this task was beyond the processing power of the Macintosh, animations were created on Silicon Graphics workstations.
Essentially, the animation consists of a series of loops of film, each loop being a rotation of the object at a given camera angle. Loops were taken at 10 degree increments, between 0 degrees and 90 degrees (see Figure 7). Controls allow the user to move sideways by going back and forward around a given loop, or to move up or down by jumping between loops. This gives the student the illusion of turning the object around in their hands.
Figure 7: Several loops of film, taken at different azimuthal angles
This technique has been used to let the student explore the relationship between two and three dimensions. Given the three dimensional object such as that in Fig. 6, the student is asked to determine a particular view of the object, for example, the plan view. On the one hand the virtual object can be manipulated until it coincides with the plan view; on the other, the student is given a number of choices of views, and asked to choose the correct one.
The programming methodology used (Phillips, 1994) explicitly sets out to make it easier to revise work. It is based on the following design aims:
Figure 8: Generic formatting tool palette
Similar functions are being developed for other program objects.
Brian Ferguson's expertise at Computer Assisted Draughting helped immeasurably in producing many of the diagrams. The virtual reality computer modelling was made much easier through the assistance of Mark Johnson, who had access to computers much faster than mine, which saved me many hours of work.
This work would have been more difficult without many helpful discussions with my colleagues in the Computing Centre, notably Sue Perry, Martin Hill, Nick Jenkins and Ken Taylor. Angela di Giorgio's graphic design assistance is especially appreciated.
Some of the work in this project has been funded by the Curtin University Research Grants Scheme, which is hereby gratefully acknowledged.
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|Author: Dr Rob Phillips, Computing Centre, Curtin University of Technology, GPO Box U1987, Perth WA 6001. Tel: 09 351 3101 Fax: 09 351 2673 Email: firstname.lastname@example.org
Please cite as: Phillips, R. (1994). Understanding technical drawings: Using interactive multimedia to enhance spatial reasoning skills. In C. McBeath and R. Atkinson (Eds), Proceedings of the Second International Interactive Multimedia Symposium, 409-416. Perth, Western Australia, 23-28 January. Promaco Conventions. http://www.aset.org.au/confs/iims/1994/np/phillips.html