Each molecule displayed by VMD can contain multiple sets of atomic coordinates, which may be played back to animate the molecule and show its motion. The source of the coordinates can be, for example, from a molecular dynamics simulation, or simply multiple versions of the same molecular structure. The Animate form is one way to control the playback of these trajectories.
The Animate form handles the trajectory playback of the active molecules. The second line of controls contains five buttons which act like the buttons on a tape player or VCR. The center button (with the square) stops the animation. The button to the right of the stop button advances the animation one step forward in the trajectory, and the next button to the right continually steps the animation forward. Similarly, the buttons to the left of the stop button steps the animation backwards either once or continuously. (Just remember that the button that looks like fast-forward is really the play button, and that the one that looks like the play button is really the single step forward button.)
The molecular status shown in this form reflects the state of the top molecule. Commands entered via this form, however, affect all active, not just the top molecule. This makes it possible to position several different molecules at the same frame, and to start them in motion at the same time with one command. But, since it is not immediately obvious from the information shown in this form what molecules will be affected, some care must be taken to make sure you have the proper molecules active that you wish to animate.
