....address to ØzCUPE3 .....QUT - April, 1997....

The Physics of Movie Stunts

Suzanne Hogg, Cindi Drennan, Andrew Francois, Justin Maynard

University of Technology, Sydney

1. Background

To inspire students about the value of Physics, Suzanne Hogg uses a wide range of approaches and media. A lecture demonstration entitled "The Physics of Movie Stunts" which is based on her work with a Stunt Agency proves as popular with school audiences as it does as an after-dinner address for Rotarians. Issues such as safety, visual effectiveness and accuracy are considered in the context of the physics of each stunt.

Earliest work in modelling the stunts used a traditional spreadsheet approach but stunt professionals responded very enthusiastically to initial attempts to make the results more "visual" by simple animation using hypercard. Recent modelling has included more accurate simulation using the package Interactive Physics II.

First year students at UTS enjoy new-style laboratory "pracs" based on the stunt modelling work, [1],[2],[3]. Because of the continued favourable response to the stunts material a request was made to the Interactive Multimedia Unit at UTS to make this a more professional presentation, not limiting it to the requirement that the one presenter had to come with the package. The process of this development is the subject of this paper rather than the package itself. It is hoped that experience gained by both the physicist and multimedia team involved here will prove useful for other developing teams who wish to "encapsulate" a presentation which is working well "live" into a more universally available package.

2. The IIM Perspective (Cindi, Andrew and Justin)

2.1 Involvement of the IIM

The project development has been a collaboration between the Faculty of Science and the Institute for Interactive Multimedia at UTS. The IIM is an academic support unit, established during 1995, with aims which include the enhancement of the quality of teaching and learning at UTS, through the use of interactive multimedia tools. Suzanne received internal funding in 1995 to advance her work with stunts simulations to the next level of production. This was sufficient for several weeks development and production time for a team of Project Leader (Cindi) , Graphic Designer (Andrew) and Multimedia Programmer (Justin).

2.2 Where to Start - Defining the Project

The first step in the development of the Physics Stunts tool, was to identify the purpose and objectives, in relation to the budget and time frame.

The Physics Stunts program was defined as being a program that would be used to promote the uses of Physics and inspire prospective students about the value and practical application of physics in the real world. The primary audience is high school students aged 12 - 17 years old. Usage of the program would be twofold - · as a presentation tool for speaker support, in an auditorium or classroom situation, · a stand alone interactive display that could be run at school open days or workshops.

From the design teams perspective, Physics Stunts is unusual in serving such different functions. A presentation program needs to be designed for situations in which there is poor lighting, and it will be displayed on a medium to poor resolution video projector, projected onto a large screen. Readability of text is a key issue - small size fonts won't be legible. Certain colours and colour combinations are inappropriate for video display because they "buzz". Fine horizontal lines are a problem, due to interlacing on video. Sound is a problem in an auditorium situation. And the navigation needs to be very simple on a program designed for speaker support - to be more like a slide show than a web like structure, with easily identifiable simple controls.

On the other hand a stand alone presentation tool is designed to be used in a one to one situtation. A key issue is to make it appealing to the target audience and easy to use, so that a user is not frustrated at being unable to navigate through the options. A time out function may be useful to return to the main menu after a preset time, as well as an "attractor" screen to draw participants in to use the program.

2.3 Overall Design and Production

The other factors affecting the overall design and production were of course budget, resources and time. IIM's contribution was time, expertise and production facilities. Suzanne brought the majority of the content (in the form of video snippets) and the ideas and subject matter expertise. The project was mapped out into development, design and testing stages and production commenced in January 1996.

2.3.1 Project Management

Once initial objectives and audience were identified, the process was fairly straightforward, involving a typical iterative design process adopted by IIM - to look at related issues (costs, development and delivery platforms, and copyright issues), develop functionality, navigation and layout, test a prototype with users, make modifications, and program the final product. The delivery platform was determined to be Power PC 6100 or higher CPU (Mac Only), to run from the Hard Drive for optimum performance. The use of high quality movies and sound means that content running from a CD-ROM would need to be driven from an 8 X spin CD-ROM drive, or higher.

Appealing to the target audience was a major factor in the overall style of the program. The topic area itself generates a lot of interest. Action Movies and danger grab the attention of the user or viewer. The stunts are timed to generate interest and excitement without putting the user in passive mode. Layout, navigation and functionality of the program was determined by the objectives and audience of the program - solving the problems as simply as possible. Navigation and controls went through a couple of iterations after user testing.

2.3.2 Design

To make the program suitable for use as a presentation tool, layout and graphics were chosen that would suit the stand alone mode, these being then tested using a number of projectors in auditioriums and venues. Colours and fonts used in the final version were the best solution to provide clarity on both a video display, and a high resolution monitor. The program was designed to have a simple but gadgetty "star trekky" kind of feel to the interface. Certain elements are more apparent on a high resolution monitor, such as the "tips" text - in a small font, and textural elements of physics equations. These would be distracting in a presentation mode, so have been designed to be visually unobtrusive when displayed on a video monitor. Interface and style have been kept simple, effectively demonstrating the principle that an interface does not have to have a fully rendered three dimensional environment in order to capture the imagination.

At all times the dual function of presentation tool and stand alone interactive presented a number of design problems. In addition to the choice of appropriate fonts the program needed to have simple functionality for speaker support as a presentation tool, while not seeming like a slide presentation when stand-alone.

2.3.3 The Material Content

Physics Stunts content falls into three areas: ·

There are about a dozen examples of the Action Movie stunts, serving to excite and "hook-in" the audience. They use sound and dynamic images to convey a message of danger and excitement. These were provided on Hi Band Umatic and needed to be digitised. Once the layout was finalised the movies were then scaled to size and cleaned up. The hardware used for digitisation was Radius Video Vision, and Adobe Premiere was used for editing and cleaning up all the video. Digitisation and processing took about ten days.

The Stunt Agency with whom Suzanne works have always been most cooperative in using the film material in the presentations. All segments used are from the Promo tape for the agency and are currently used to introduce the 1st year physics lab which is modelling stunts.

The physics "models" relating to each filmed stunt segment allow the user to explore the causes and effects of how the stunt works - and the "What if .... ? " side of any stunt jump. The use of Interactive Physics II to produce these models adds considerable reality to the supporting calculations behind any stunt.

2.4 Putting It All together.

In putting together the program at IIM, it was necessary to integrate the whole package of video and stunt model into a form that was simple to use and robust. Director 5.1 was chosen as the principal tool as it allowed the best advanced control of Quicktime through its coding language "lingo".

2.4.1 Interactivity Tradeoff

Director does not easily allow transition from itself to launching another program and returning, so there would have been problems running the video in Director and swapping to and from Interactive Physics for the simulation. To solve this technical limitation, it was decided to place video "simulations" of interactive physics as Quicktime Movies into the final program. This is less interactive than the Interactive Physics program itself, but still allows exploration and play by users while giving a basic idea of the functionality of the program.

2.4.2 Limitations of Interactive Physics

Interactive Physics does allow export of its simulations to a Quicktime format, but this has been included as a way of saving experiments, not as a tool for generating interactive multimedia content. Being designed specifically for a scientific application, there is very little control within Interactive Physics over aesthetics After several days research into the export capabilities of Interactive Physics, it was found useful to create a template that defined safe action areas for model creation. This was a workaround for a tool that was never designed for multimedia quality. Exported Quicktimes from Interactive Physics were in 256 colours, with dithered fills and text that would not scale well, so everything had to be created at exactly the size and format at which it would appear in the final program.

The use of Interactive Physics quicktime movies as a simulation of the actual program posed several other interface design problems as well. In particular, how to provide functional controls into the model movies to give users controls to change certain model parameters. The programming solution decided upon used linked audio and video quicktime movies, actively tracked and controlled by lingo, to allow controls to be placed directly over the model movies. This had merit over other solutions such as picts replacing movies, or mouse tracking as it was the most stable solution and also re-useable if the product is ported to the PC platform.

2.4.3 Text

Text elements to place the movies and models into context have been scripted to highlight the critical aspects of the stunts, and the practical application of the mechanics of physics. Smaller font size questions give a greater level of exploration and ideas and are directly relevant to the stand alone product user yet are designed to be unobtrusive on the presentation display.

2.5 User Testing

User testing of our first prototype highlighted several issues which have been addressed in the latest iteration of the program. The first major changes were to display the stunt movie and the model movie on the same screen so that users could see all the information relevant to a single stunt on the same screen, and also to build sound control and quit functions into the splash screens.

The second major change has been the use of sound in the Interactive Physics models. This was partly to address an imbalance of impact between the stunts videos, which were dynamic and powerful and the physics model which in comparison seemed colourless and boring. Sound effects were employed to heighten the impact and emphasize the success or failure of a stunt in terms of safety or visual effect. The use of sound to convey a sense of space, environment and emotion was an effective solution to the problem, and highlights the fact that in interactive multimedia, sound is as important as image in conveying information.

3. The Physics Perspective

Working with the IIM to create a successful multimedia format for the Physics of Movie Stunts presentation has been a most interesting experience, some of the expected outcomes being difficult to achieve but this balanced by extra features which had not been expected. Much of the difficulty experienced has been as a result of the use of the Interactive Physics Package as providing the analysis of the physics stunts. Disadvantages are however somewhat balanced by the confidence in maintaining physics reliability in the model. It is hard to contemplate the recalculations needed by the use of more manual forms of model animation.

3.1 Unexpected Requirements

The need for apparently narrowing the audience down by defining a singular purpose was the first of many learning experiences. The IIM took on the challenge of providing two modes of play - which compounded their problems in decision making throughout the process.

Copyright issues were also more complex than expected. Having a licence for the use of Interactive Physics it was assumed that this should give the licensee the right to use freely the movies output. It seems that Knowledge Revolution is somewhat perplexed on this issue as two requests for permission have not produced any response other than an acknowledgment of the receipt of the request.

3.2 Trading Off Interactivity for Presentation Appeal

The original request was for the student hands-on version of the programme to be able to call in the Interactive Physics Player so that the student could explore the models with all of the tools available in that package. Choice of Director as the best tool for incorporating all of the material meant that the real link to Interactive Physics was not possible. While this was a great disappointment, the essential physics is probably clearer with the students being given a restricted set of choices in the control values such as speed and angle. Choosing which parameters to vary and the values to give most interest is the greatest challenge for the physicist.

3.3 Advantages and Disadvantages of Interactive Physics as the Modelling Tool

3.3.1 Appearance vs Accuracy

Interactive Physics is a powerful modelling tool - and can be made to look quite attractive in linear motion by the attachment of artwork to the otherwise boring rectangular and circular objects. While it is possible to construct much more complex objects from the polygon and freehand tools provided, the complexity of the calculations for the engine provided in Interactive Physics cause the animation to become painfully slow, particularly on the first run of altered parameter settings. The attached pictures are cosmetic only and therefore do not slow down the calculations - but they do not rotate with the object and are therefore able to be realistically added only in certain stunt scenario. It was decided to keep consistent format by not including pictures at all.

3.3.2 Difficult Modelling Situations

Motion on curved surfaces is almost impossible to realise in Interactive Physics. Such motion takes considerable skill with application of formulae to the motion. In addition, the action of springs and constraints are theoretically quite controllable - but prove frustrating in adjustment to model real springs. Some quite bizarre motions have appeared when the graphics designer slightly tweaked a spring, resulting in a force which gave motion where no motion was expected.

3.3.3. QuickTime Movie Output

The revised format of the output was possible because of the ability to save the Interactive Physics motion in Quicktime format. The limitations of the quality of such movies for inclusion by the designer and programmer has, however, been described above - and is obviously of importance when producing something on the multimedia platform.

3.4 Future of Multimedia in the Physics Teaching Process

Physics is often ridiculed as being obsessed with simple pendula and inclined planes. It is possible by using multimedia techniques to show how exciting very basic physics is, how useful are the concepts of projectile motion and falls under gravity. Whether we can afford to do so is another issue - to produce a professional product takes a lot of skill.

Having hopefully produced an exciting multimedia production in 1997, however, the worry is - how exciting will it remain in the world of multimedia in 1998? Will the shelf life make such a venture worthwhile?

[1] R.W. Cheary, M. Gosper, E. Hazel and L. Kirkup (1994) "Learning Physics in the Laboratory" Proceedings of the International Congress on Educational Strategies and Misconceptions in Science and Mathematics, Cornell University, Ithaca, USA.(1 - 4th August 1993)

[2] R.W. Cheary, M. Gosper, E. Hazel and L. Kirkup (1994) "Reforming the Physics Laboratory: From Theory to Practice" Proceedings of the International Congress on Educational Strategies and Misconceptions in Science and Mathematics, Cornell University, Ithaca, USA.(1 - 4 th August 1993)

[3] R.W. Cheary, M. Gosper, E. Hazel and L. Kirkup (1994) "Reforming the Undergraduate Science Laboratory" Research and Development in Higher Education. 16, 129-134.