Animating objects along a trajectory, also known as path animation, can add dynamic movement to your compositions in Adobe After Effects. Here’s a step-by-step guide on how to achieve this effect:

Creating a Motion Path:

1. Create a New Composition:

   • Open After Effects and create a new composition.

2. Import Your Assets:

   • Import the assets you want to animate into your project.

3. Create a Shape Layer:

   • Create a new shape layer by clicking on the “Rectangle” or “Ellipse” tool in the toolbar, and then click and drag on the composition to create the shape.

4. Convert Shape to Path:

   • Convert the shape layer to a path by selecting the shape layer, right-clicking, and choosing “Create > Create Shapes from Vector Layer.”

5. Adjust the Path:

   • Open the “Contents” of the shape layer, then open the “Shape 1” and “Path 1.” You can adjust the path by modifying the shape’s anchor points.

Animating Along the Path:

6. Position the Object:

   • Place the object you want to animate at the starting point of the path.

7. Parenting:

   • Parent the object to the shape layer by dragging the pickwhip from the object’s layer to the shape layer. This links the object to the motion path.

8. Animate Position:

   • Open the object layer’s Position property. Move the playhead to the starting point in the timeline, set a keyframe for Position, and then move the playhead to the ending point and adjust the position. After Effects will automatically create motion along the path.

Fine-Tuning the Animation:

9. Adjust Keyframe Interpolation:

   • Open the Graph Editor to fine-tune the animation’s speed and smoothness. Adjust keyframe interpolation for the Position property to control the easing.

10. Add Rotation or Scale:

    • Enhance the animation by adding rotation or scale keyframes to the object layer. This can create a more dynamic and engaging motion.

Advanced Techniques:

11. Use Null Objects:

    • Create a null object and parent the shape layer to the null object. This allows you to control the motion path independently and provides more flexibility in animation.

12. Adjustable Motion Path:

    • Instead of using a shape layer, use a mask on a solid layer. This allows you to easily adjust the motion path by modifying the mask points.

Working with Multiple Objects:

13. Duplicate Layers:

    • Duplicate the object and shape layers to animate multiple objects along the same trajectory.

14. Offset Animations:

    • Offset the keyframes for each duplicated layer to create a staggered or sequential animation.

3D Motion Paths:

15. Enable 3D Layers:

    • If you want to add depth to your animation, enable 3D for the layers. Select the layers, then toggle the 3D switch.

16. Animate Z Position:

    • Animate the Z Position property to create a 3D motion path. This allows objects to move in three-dimensional space.

Rendering and Exporting:

17. Preview Your Animation:

    • Use the RAM Preview feature to preview your animation within After Effects.

18. Render Settings:

    • Set up render settings in the Render Queue for exporting your final animation.

19. Export and Share:

    • Export your animation and share it in your preferred format.

By following these steps, you can create captivating animations where objects follow a trajectory or motion path in Adobe After Effects. Experiment with different shapes, paths, and object properties to achieve the desired visual effect for your project.