When the animator plans his/her action, figuring out all the drawings that will be needed to animate the scene, including the in-betweens.

It seems like you're asking about the process an animator goes through when planning and creating a scene. Here are the steps:

1. Conceptualization: The animator first comes up with the idea or concept for the scene. This could be based on a script or storyboard.

2. Planning: The animator then plans out the action in the scene. This involves deciding what movements the characters will make and how they will interact with their environment.

3. Sketching Keyframes: The animator sketches the keyframes, which are the main points of action in the scene. These are the most important drawings as they define the start and end points of any smooth transition.

4. Drawing In-Betweens: The animator then draws the in-between frames, which are the drawings that create the illusion of movement between the keyframes. The number of in-betweens can vary depending on the speed and smoothness of the action.

5. Review and Refine: The animator reviews the animation, making any necessary adjustments to improve the fluidity and realism of the movement.

6. Finalizing: Once the animator is satisfied with the animation, they finalize the drawings, adding color, shading, and any other necessary details.

7. Rendering: The final step is to render the animation, which involves processing all the drawings into a single, smooth animation. This can be done using animation software.

Remember, this is a general process and can vary depending on the animator's style, the complexity of the scene, and the specific requirements of the project.