Autodesk 62205-051408-9001 User Guide - Page 288

12 Creating Animations Keyframing in Combustion is the same as in 2D cel animation: you set your characters when they "hit their marks" and Combustion does the in-betweening. Interpolation modes add character, control, and realism. About Animating This chapter discusses animating using keyframes. A keyframe is a point in time that records any change to a layer, light, camera, or Paint object. All these elements of your workspace can be broken down into categories, which are specific parameters that define the appearance of the layers or objects (such as size, position, or color). Layers and objects can have many different categories. In some cases, there are subsets of categories. These are called channels. Note: In the Timeline, the word channel is used to refer to subsets of categories that you can animate. However, a channel also refers to the alpha channel or the RGB channels of an image. When you animate the position of a layer or object, you do not simply animate the layer's position-you animate its position along the X-axis, the Y-axis, and the Z-axis. Position is a category; X position is a channel. To make a layer or Paint object appear gradually over a span of two seconds, you have to make it fully transparent on the first frame, then move ahead two seconds into the video and make the layer fully opaque. Frames at which you set the opacity become keyframes. The opacity values for the frames between the keyframes are calculated automatically using interpolation, which creates smooth motion. To change the animation, go to the first or last keyframe and change the opacity for the layer. All inbetween frames are recalculated automatically. You can also animate by adding expressions to channels. For information on using expressions to animate channels, see "Creating Animations" in Chapter 12, "Creating Animations''. Keyframing in Paint You keyframe Paint objects, selection objects, and mask objects in the same way you keyframe layers in a composite. Unless otherwise specified, when referring to keyframing layers in this chapter, the procedures also apply to Paint, selection, and mask objects, as well as emitter objects in the Particles operator. For information on creating Paint objects, see "Creating Paint Objects" in Chapter 17, "Paint: Drawing Basics''. Enabling Keyframing Before you can set keyframes to create any animation you have to enable the Animate button. When enabled, the Animate button is red. Note: You can also press A to toggle the Animate button. When this button is turned off, you can adjust any category at any frame, but the value does not change over time. The value of the category is set to the last specified value for the entire clip; when keyframes already exist, the value of the category is offset over the entire clip. 272