The frame rate of an animation is expressed in frames per second (FPS). This is the number of frames 3ds Max displays and renders for every second of real time. Because 3ds Max stores your animation keys using real time using an internal precision of 1/4800 of a second, you can change the frame rate for your animation at any time without affecting your animation timing.
For example, if you create three seconds of animation using the NTSC video frame rate of 30 FPS, you will have a 90-frame animation. If you later discover you need to output to PAL video, at 25 frames per second, you can switch to that frame rate, and your animation is now set to 75 frames of output. No change in the timing of your animation has occurred. Only the number of frames that 3ds Max will display and render has changed.
Real Time: Animation plays at the selected playback speed, skipping frames, if necessary, to maintain the correct speed. Turn this off and the animation will play every frame without trying to maintain the correct speed. The different playback speeds are also useful when using the .
Direction: When Real Time is off you have the option to change the direction of the animation playback. Choosing Reverse will play the animation from end to start. Choosing Pingpong will play the animation from start to end, and then end to start.
The ability of 3ds Max to play your animation at a specified rate depends on many things, including the complexity of the scene, the number of objects moving in the scene, the geometry display mode, and so on. The worst case is a camera move in shaded mode, in which the viewport is filled with detailed geometry. In such cases, it’s best to simplify the viewport display, using either wireframe display or, in extreme cases, box display mode.
Naturally, it takes more computing power to display your animation in four viewports, and playback smoothness is reduced. When Active Viewport Only is on, you can switch active viewports during playback either by clicking the label of an inactive viewport, or by right-clicking in an inactive viewport.