Computer Animation

Computer animation has become commonplace on TV and in movies. Two of my favorite animations are the commercial in which the Statue of Liberty picks up an Oldsmobile Aurora automobile for a closer look, and the launch sequence from the movie Apollo 13. Apart from entertaining us, computer graphics and animation help us solve and explain engineering problems with visualization of a process or event. They allow us to perceive objects in relation to their surroundings in a clear-cut presentation. Computer animation can be used to explain things such as: the complicated molecular structure of DNA, the interaction of parts in a mechanical system, how a building is constructed, or the path of an accident vehicle. Animation can help a trial lawyer, inventor, or research scientist tell their story.

This color image is from a 3-4 minute animation produced by Unified Engineering. The purpose was to explain the workings of a hammermill used to crush and shred material fed in from the top. The ducts, mill housing, and pulley guard have been made semi-transparent to show the target audience the movement of material through the mill, the movement of the hammers to crush the materials, the exiting of the shredded material from the bottom of the mill, and the way in which power is transmitted from the motor to the mill. Used as an exhibit with engineering testimony it provides a clear understanding of the overall area and specific accident details.

You can view a short clip from that animation on your computer by downloading a file in either QuickTime or AVI format. Each file is about 1 megabyte and runs for about 15 seconds in a 320x240 pixel window. To keep the downloading times short we've reduced the size and quality of the images. The original animation ran in a 640x480 pixel window and was over 280 megabytes.

The animation previously described is built and produced inside a computer. The process is comparable to producing a movie. First you determine the overall story line, then you build and arrange the movie set and finally you set up the lights, camera and shoot the action. The concepts and message you want to convey will determine the overall complexity of the animation.

Models in the animation can vary from simple shapes to complex photo-realistic objects. Models are built by drawing three dimensional objects in the computer. Dimensional data required to accurately build these models can be obtained from many sources including drawings, photographs, video, and actual parts. The models are arranged in the scene and scripted for motion if required. Lighting, object skin texture and color are adjusted to obtain the desired effect. Finally, camera perspective, position and motion are set to record the scene.

"Shooting the action" is a process called rendering, during which the computer generates a digital image for every scene the camera views while taking into account the model's position, visibility, color, transparency, lighting, etc.. Smooth motion video requires thirty still images for every second of animation. Rendering is typically time consuming where the computer works continuously for hours to produce a few minutes of animation. The final rendered animation can be shown on the computer monitor or copied onto video tape for viewing from a VCR/TV monitor.

This article has glossed over the numerous controls available at every level of the computer animation process. There are clearly many advantages of using computer graphics over photographs and physical models. The goal of a technical animation is to have the viewer say, "Now I understand."