The Auto Key button toggles the keyframing mode called Auto Key. While Auto Key is on, changes to objects’ position, rotation, and scale are automatically keyframed (recorded). When Auto Key is off, these changes are applied to frame 0.
Alternatively, you can create keyframes manually with Set Key mode, which allows you to add keyframes explicitly with the Set Keys button.
When Auto Key mode is active, the Auto Key button is red, as are the active viewport outline and the time slider. These indicators serve to remind you that you are in Animate mode, and that you are setting keyframes with your actions.
Within an existing animation, you can create keyframes for transforms without the use of Auto Key mode by right-clicking the time slider and then setting the source and destination time. For example, you can use this function to copy an existing Move key to a later frame, so an object pauses its motion momentarily (to keep the object still, you must use linear or step interpolation). You can also set keyframes for other animatable parameters in Track View and the Motion panel without using Auto Key.
To animate an object using Auto Key:
The Auto Key button, the time slider, and the highlight border around the active viewport all turn red.
For example, assume you start with a cylinder that has not been animated yet and therefore has no keys. You turn on Auto Key, go to frame 20, and rotate the cylinder 90 degrees about its Y axis. This action creates rotation keys at frames 0 and 20. The key at frame 0 stores the original orientation of the cylinder, while the key at frame 20 stores the animated rotation of 90 degrees. When you play the animation in the viewport, the cylinder rotates 90 degrees about its Y axis over 20 frames.
Example: To animate an object between three points using Auto Key:
3ds Max creates a Move key at frames 0 and 25. The establishing key at frame 0 describes the object's position at point A. The key at frame 25 describes the object's position at point B.
3ds Max creates a Move key at frame 50 that describes the object's position at point C.
The object moves from point A to point B over frames 0 to 25, then proceeds to point C over frames 26 to 50.
The position of the object in between the keyframes is determined by the interpolation type used by the controller. Right-click the keys in the track bar and select the transform key to see the controls for adjusting the timing of the in-betweens.
To remove the animation from a scene and start again:
All the objects remain in the scene, but all keyframes have been removed.
Example: To animate a deformation curve of a loft object:
To animate a hierarchy with IK interactively: