About combining keyframes and behaviors
When you combine keyframes with behaviors, Motion adds the two sets of instructions together. For example, if you apply a Throw behavior toward the upper left of the Canvas, and at the same time add keyframes that instruct the object to move to the right, the behavior-driven object moves less leftward because the keyframes are pushing it in an opposite direction. The larger the Throw velocity rate, the more the behavior overpowers the keyframes, and vice versa.
You can use this method to enhance and control the effects of behaviors. For example, you can apply a Gravity behavior that causes an object to fall toward the bottom of the Canvas, and then keyframe the object’s position to move across the Canvas from left to right. As a result, the object falls as it moves rightward.
Likewise, you can apply a Fade In/Fade Out behavior, but use keyframes on the object’s Opacity parameter to limit the maximum opacity to 80 percent. The resulting clip fades in, but not completely.
Additionally, you can convert behaviors to keyframes. See Convert behaviors to keyframes.