CAD tip # 5212:

But you can also save an animation of your manual walkthrough or flyover. Although the 3DWalk and 3DFly commands do not explicitly offer animation recording, you can use the Dashboard interface for this.

In the Dashboard "3D Navigation" panel (with pan, zoom, walk icons) hover over the leftmost "compass" icon and then click on the double down-arrow control. The animation controls will appear. Set the step size and steps per second sliders to adjust the animation parameters, start the 3DWalk command and click the red "Record" button in the Dashboard. Now walk as usual (the WASD keys) through your model. Click the Play button to replay the recorded animation and finally save it to a disk video file with the black square Save button.