3D Animation Workshop: Lesson 7: Bringing It To Life | 3
Lesson 7 - Bringing It To Life - Part 3
Let's expand the concept by creating a second keyframe at frame 4, exactly halfway through the animation, in which the object moves vertically a bit, up the y axis.
This gives a rough sense of a bouncing ball. But we can learn a very important and often conceptually troubling concept about keyframes. Now that there are two keyframes, there are two interpolations. The first path, from frame 0 through frame 3, and a second one from frame 3 to frame 6. There is one sequence consisting of two interpolations because we have been altering only one parameter, the location of the object. But we can alter different parameters on different keyframe sequences that overlap each other.
To make this clear, let's animate the color of the sphere as a separate parameter. The first frame (frame 0) will be as before, but the color of the object in frame 6 will be changed to yellow.
There are now two different parameters being animated on separate tracks. The translation of the object is being animated using keyrames at 0, 3 and 6, and thus is being accomplished in two steps over the course of the animation. The color is being animated in a single step that is interpolated across the entire 7 frames, beginning at 0 as red and ending at 6 as yellow.
The keyframing, and the therefore the animation, of different parameters independently is one of the things that makes the process so power and fluid. Translation, rotation, scaling, and shading of objects, the movement of the camera, the movement and intensity of the lights--all these can be animated separately by keyframing these different parameters.
For example, let's decrease the intensity of the spot light over the course of the animation by cutting its intensity down to zero at frame 6.
As with the color parameter, the light intensity is being interpolated continuously over the entire animation. To make it more interesting, lets make the light flare up at frame 2, setting a new keyframe there with the light intensity doubled.
Now, as we did with translation, there are two interpolations for the light intensity. The light begins at 100 percent intensity, quickly jumps to 200 percent intensity by the third frame (frame 2), and then declines all the way to zero by the end of the sequence. Note that we still see some color in the ball at the end due to the ambient lighting, though without the spotlight, the sphere is not longer evident as a three dimensional object.
Let's add one more parameter to the mix. By scaling down the sphere in the y axis (vertical), it appears squashed.
Let's change our initial frame to adopt this scaling, set a keyframe for the original scaling at frame 3, then set a final keyframe at frame 7 with the squashed scaling again. Thus the scaling parameter will follow the track of the translation parameter--stretching out as the ball rises in the vertical axis, and squashing back down as it falls.
We've learned a lot here with some very small and crude animations. Using a simple primitive and only 7 tiny frames we've animated four different parameters--translation, scaling, light intensity and color. Now we have enough background to start thinking about some worthwhile projects. We'll start on some real animation ideas next time.
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Created: April 8, 1997
Revised: March 6, 1998