3D Animation Workshop: Lesson 7: Bringing It To Life | 2 | WebReference

3D Animation Workshop: Lesson 7: Bringing It To Life | 2

Lesson 7 - Bringing It To Life - Part 2

We are now ready to try our first animation, using the background established in the earlier tutorials, and adding the concept of KEYFRAMING. Keyframing can be thought of as adding a fourth dimension to our work--time. Thus far we have considered the creation of 3-D models having geometry and surface attributes (such as color and reflectivity). We have also become familiar with placing these models at locations in a scene (3-D coordinate space) where they can interact with light sources placed in the scene and be viewed (rendered) by the camera, which also has a location and orientation in the 3-D coordinate space of the scene. All this will result in the rendering of a single picture or "frame." But let us expand our horizons into another dimension by thinking of this scene as only one moment in time.

To create an animation, we make changes in the scene and associate them to another moment in time. This association of the changed scene with a new moment in time is called "keyframing." As animation is presented as a sequence of frames running at a speed fast enough to deceive the eye into a sense of continuity, the concept of time is merged into the concept of frames. At a standard videotape speed of 30 frames per second, frame 30 is the equivalent of 1.0 seconds into the animation, and, conversely, the 1.5 second point in the animation is at frame 45. Thus by fixing the state of the action at one moment in time meaning assigning it a frame number at a given frame rate in rames per section. Hence keyframing is the process of changing the scene and assigned the changed scene to frame number in the animation. Note that the GIF format animations in these tutorials, like other animations run on standard consumer computers, must run at speeds well below that of standard video--typically at 12 to 18 frames per second.

When the animation is rendered, the application will "interpolate" between keyframes. This is the same function called "inbetweening" in traditional drawn animation in which artists drew the intermediate frames between the more significant ones first created in a storyboard. The subject of interpolating between keyframes is one of the most important concepts in 3-D animation but we will pass over the complexities for now and stick to the simple idea that the application simply creates incremental frames between the assigned keyframes. For example, assume a simple red sphere is created and placed at the origin (0,0,0). A camera is fixed above and to the left, pointing at the origin. The lighting is a simple combination of a spot light from behind and some ambient light to fill in the shadows. The location in time is a frame 0.

Next we move the sphere to the right of the frame and set a keyframe at frame 6.

Notice the funny use of language suggesting the unique merger of time and space concepts in 3-D animation. I speak first of moving the object to the right of the "frame," meaning the visual, spatial, viewing frame. Then I speak of frame 6, which is a frame in the time sequence. This double use of the word "frame" is going to come up again and again.

Now we render all frames in sequence, and the application interpolates the translation of the sphere for each intermediate frame.

Notice that there are seven frames here because frame 0 has been rendered in this instance up through and including frame 6.

Play these in sequence and we have an animation, which I have implemented as a repeating loop of the seven frames.

Sure this is crude and simple, but it is a miracle nonetheless. We took a simple object. We moved it to another location, assigned the translation a keyframe and let the application do the rest. The object is so small and the distance it moves across the scene is so short that even with only seven frames the movement is smooth enough to appear continuous.

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Created: Apr. 8, 1997
Revised: Apr.22, 1997

URL: http://webreference.com/3d/lesson7/part2.html