Reconstructing the world in 3-dimensions
27 April 2015
Posted by: Ted Parisee
More and more often, 3D visualizations are used to help describe the events that transpire in occurrences investigated by the Transportation Safety Board of Canada (TSB). Drawings and images are a useful tool for describing the dynamics of an occurrence. If a picture is worth a thousand words, then a 3D animation can be just as valuable, if not more so.
Steps in producing an animation
Creating an animation can be a long process since there are a number of steps from start to finish. This involves the initial planning, collecting data, 3D modelling, animating the scene, rendering, compositing, and adding audio.
The initial planning stage requires discussing with internal stakeholders (Investigator-in-charge, Communications Branch, etc…) what is to be accomplished with the animation. In some cases, only a simple animation is required to show a small part of the occurrence that is difficult to describe. In other cases, there may be a requirement to create a complex animation as part of the public release of an investigation report. It is necessary to discuss with all who are involved to determine the level of detail to be shown in the animation.
Details about the objects involved in the animation are needed to build the 3D models for the animation.
For example, a site survey and photographs for the purpose of photogrammetry would be used to measure positions of objects represented in the animation. For a scene on the deck of a vessel, detailed drawings with the dimensions and layout of the vessel would help create an accurate scene. The more detailed the animation, the more information is collected for the reconstruction.
As with the data collection phase, the more details from a scene that are incorporated into the 3D models, the more realistic details in the animation will be. A lot of time can also be spent on small details of any 3D object, as well as the scene. It’s not unusual to spend weeks working on just one model as part of the scene. Occasionally, 3D models are purchased for use in an animation. In most cases, these models are modified, or simplified, to fit in with the animation.
Animating the scene
Animating the scene is where you would think all the work comes to life. But this process can take just as long as the time spent creating the models, since each object is animated separately and everything needs to work together from a timing perspective. For example, a vehicle may have to be animated to follow a path. The position and speed of the vehicle might be dictated by an event recorder, so extra steps need to be taken to have the vehicle accelerate or decelerate along the path rather than maintaining one constant speed. Also, other parts of the vehicle may need to be animated while it follows that path, plus the vehicle will probably need to be synchronized with other objects in the scene.
Generating image sequences, where each frame produces an image, is called rendering. The standard high-definition frame rate is about 24 frames per second, so a 90-second HD animation video will require 2,160 images.
To produce the image sequences within a reasonable time frame, there are two choices: either you lower the quality and resolution of the animation video, or you use a faster computer. A high quality resolution image can take 60 minutes to render, so a 90-second video may take as much as 90 days to render. At the TSB, we use network rendering where multiple computers generate the images at the same time. With three computers to render the images at the same time, the same level of quality can be achieved in 30 days instead of 90.
Compositing is when the rendered image sequences are combined to produce the final video. Text is often added at this stage to help identify sections of the animation or to add descriptors. Compositing also provides the ability to apply motion graphics and to add special effects such as lighting, weather, smoke and fire.
Although the final stage of the animation production is the addition of audio for narrations or sound effects, it is useful to plan these at the onset of production. Cues from the animation video set the timing for audio segments to occur. Because the narration may require longer animation segments, these have to be anticipated in order to ensure the audio matches the video timing.
The use of 3D animations to depict an event or part of an occurrence has grown and evolved significantly in the last decade within the TSB. In fact, the quality has improved so much that the animations are appearing more life-like. As animations are increasingly used in the release of investigation reports, investigators appreciate the value of TSB’s photogrammetric capabilities and ability to conduct site surveys used in the production of an animation. In the end, the animations go a very long way to prevent an occurrence from happening again by helping to explain what happened and why.
Here’s an example of a TSB 3D animation representing the sequence of events in the Lac-Mégantic derailment and fire.
Ted Parisee is a Senior Engineering Technologist with a specialty in geospatial data. He has been with the TSB since 1999 after joining as a contractor during the Swissair investigation. Ted has a Computer Science degree from Dalhousie University in Halifax, Nova Scotia, and moved to Ottawa in 2002 with his wife Cassandra and two boys Jordan and Andrew. Ted enjoys playing Call of Duty on the occasion and he welcomes any challenges.
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