To achieve the effect where a character's head flips to follow a target without "breaking" the neck, especially when the target moves to positions straight up or down relative to the character, you can utilize a combination of Spine's rigging features and Unity's scripting capabilities.
In Spine, you can set up Inverse Kinematics (IK) constraints to make the head follow a target bone. This setup allows for dynamic movement and orientation of the head based on the position of the target bone. You can refer to the Spineboy example for an illustration of how IK constraints are used for aiming and following a target (Spineboy example: Aiming).
However, to flip the head based on the target's position (especially for extreme angles like straight up or down), you might need to implement additional logic in Unity. This could involve checking the angle between the character and the target and then flipping the head bone accordingly. This logic can be implemented by modifying the scale or rotation of the head bone in Unity's script when certain angle thresholds are crossed.
For a smooth transition and natural movement, you might also consider adjusting the IK constraints' mix values dynamically based on the target's position, ensuring that the head movement blends seamlessly with the rest of the character's animations.
