Introduction to Forensic Animation Technology

A forensic animation is the use of full motion computer graphics to recreate an event or to explain the inner workings of a device or process. Ironically, the same software used to create feature films such as Lord of the Rings or Spiderman is also used to create accurate and detailed animations which are admissible in court. There are basically two types of animations, substantive and deive. A substantive animation is where physically accurate simulation software is used to provide the movement of objects based on data inputs. A common example is an automobile collision where the accident reconstructionist begins by collecting all the necessary data such as the terrain geometry, road conditions, vehicle specifications, impact speeds, friction coefficients, etc. This data is then input into the simulation software and the output is a set of data which describes the motion of objects. Many simulation programs also have the option to graphically animate the results of the simulation although, most are still lacking in the level of realism. Alternatively, the data may be output to another 3D animation program which can provide a much more realistic and higher quality animation. It is important to understand that the movement of objects is calculated based on dynamics and physically accurate mathematical equations. Deive animations (which are perhaps the most common), vary from showing how a mechanical device may have failed to how a medical procedure may have gone wrong. These are simply informative recreations based on data supplied to the animator and normally confirmed by an expert. Deive animations may also be used to recreate vehicle collisions; however the animator or accident reconstructionist would provide the basis for the movement and timing of the vehicles as opposed to a simulation program.Regardless of which type of animation is used, they still need to be accurate and should normally have solid data or reference materials to aid in there construction.When to consider a forensic animation?There are 4 areas where forensic animations are extremely useful. These are cases which are usually related to:1. Timing2. Perspective3. Distance/Position3. Process/ MechanismImagine trying to explain the view a person may have had while driving behind a transport truck. Perhaps, it is important that a jury understand how a particular chemical reaction takes place or maybe it is important to describe the relative distance and position of particular objects prior to and after an industrial accident. In each case, using words alone can be difficult to give a clear understanding of the events as they occurred: Potential view of a driver just before impact. Being able to show animations in real time and having the ability to demonstrate difficult to explain items in a clear and concise manner is certainly advantageous. The audience receives a clear understanding of the message which will be retained in memory for a greater length of time.Why Forensic Animations?There are many different reasons as to why an animation is helpful when dealing with a legal case. Being able to see how something may have happened brings to light other questions and possible scenarios which may not have been thought of prior to seeing the animation. Often, a forensic animation can highlight the strengths and weaknesses in an argument and provide clues as to where one should be focusing their attention.There have been several studies regarding animations and their use in court. What is typically found is that a visual presentation of facts is better understood and retained for a longer period of time than a verbal account of facts alone.A 1992 study, known as the Weiss-McGrath report, found "a 100 percent increase in juror retention of visual over oral presentations and a 650 percent increase in juror retention of combined visual and oral presentations over oral presentations alone. In another study, it was shown that jurors who experience combined visual and verbal presentations retain 85% of that information as opposed to retaining only 10% with oral presentations alone Therefore, the visual nature of a forensic animation can persuade a jury or the opposing side to accept your position by enhancing their understanding of the facts.Forensic Animation ProcessThe beginning of a forensic animation normally starts with the collection and study of data. This may well include reviewing all police reports, witness statements, photographs, vehicle inspections, crime/accident scene data, and medical reports if necessary.The next step involves building the actual 3D models for use in the animation. There is a high degree of emphasis placed on the accuracy of the models and typically, the data which supports the creation of the models comes from field measurements, photographs, x-rays, reports or any other form of data often supplied by an expert witness. It is quite common to use CAD or solid modeling packages such as AutoCAD or SolidWorks to create highly accurate 3D models which can later be imported into the animation software. The models are then assembled in the 3D animation software (e.g. 3DS Max, Maya, Lightwave) and normally placed in their relative positions. Materials and textures are then applied to the models to give them a more realistic look.At this point, the “scene” is ready for animation. The animator then decides the time period for which the animation takes place. Usually, animators use a base time of 30 frames per seconds (30 fps). So, 3 seconds of animation equates to 90 individual frames. There are specific frames which the animator fixes the position of an object in order to achieve movement. For example, on frame 0, the animator could place a car at rest near a stop sign. Then at frame 90 (3 seconds later), the car could be “keyed” to be 5 metres from its original position. The actual term is called “keyframing” and is fundamental to how most 3D animation software packages work. Between each set of keyframes (0 and 90 in our example), the software interpolates the position of the car.Once animated, lighting is setup and virtual cameras are placed in the scene. The animation can now be rendered. Rendering is the process by which the 3D animation software calculates one image for each frame of the animation. The time to render each frame of the animation varies depending on the resolution and how complex the scene is. Most renders take anywhere from 2-20 minutes per frame, but there are no hard rules here since there are many different factors which affect render time. Finally, the rendered animation may be edited to add titles, text and other information. The final animation is copied to DVD, VHS or other media format for viewing by the client.The cost for a forensic animation can vary from a few thousand dollars to tens of thousands of dollars depending on the complexity and length of the animation. Time is also a consideration since most detailed animations require several days to several weeks (or months, in some cases) to produce. Ultimately, forensic animations provide a clear and vibrant method of communicating a particular point of view. The first and most important item to consider is the purpose. What are you trying to demonstrate and why is it important to your case? A poorly constructed animation runs the risk of being inadmissible in court. On the other hand, a well thought out animation with a clear purpose can be a deciding factor in winning a big case.