What Is a Key Frame?

In computer animation terms, frame-is the single image frame of the smallest unit in the animation, which is equivalent to each frame of the film on the film. Frames appear as a grid or a mark on the timeline of the animation software. Key frame-equivalent to the original painting in 2D animation. Refers to the frame where the key action in the movement or change of the character or object is located. Animations between keyframes and keyframes can be created by software, called transition frames or intermediate frames.

Keyframe

The concept of key frames comes from traditional cartoon production. In the early Walt Disney production room, skilled animators designed key frames in cartoons, so-called key frames, and then intermediate frames were designed by ordinary animators. in

Whether it is a spline-driven animation or a key frame interpolation method, this problem will be encountered: given the trajectory of the object's movement, find the position of the object in a certain frame of the picture. The trajectory of object movement is generally represented by a parametric spline. If the parameters and

In principle, the key frame interpolation problem can be reduced to the parameter interpolation problem, and traditional interpolation methods can be applied to the key frame method. But key frame interpolation is different from pure mathematical interpolation, which has its particularity. A good key frame interpolation method must be able to produce realistic motion effects and provide users with convenient and effective control methods. A particular movement may be correct from a spatial trajectory perspective, but may be incorrect or inappropriate from a kinematic or animation design perspective. The user must be able to control the kinematics of the movement, that is, change the speed and acceleration of the movement by adjusting the interpolation function. In order to solve the time control problem in the interpolation process well, Steketee et al. Proposed to use double interpolation to control the motion parameters. One of them is a position spline, which is a function of position versus keyframes; the other is a motion spline, which is a function of keyframes versus time. Kochanek et al. Proposed a class of cubic interpolation splines suitable for keyframe systems. They divided the tangent vector at the key frame into the input vector and the output vector, and introduced three parameters: tensor t, continuous c and offset b Control the spline. This method has been applied in many animation systems.