In this lesson, you will learn how to bridge the gap between player input and animation by predicting a character's future path for the Motion Matching system.
Why Predict Trajectory?
Motion Matching doesn't just play a single animation; it looks at what the character should be doing in the near future and finds the animation frame that best matches that path. To do this, we need to generate a "Trajectory"—a visual representation of where the character will be, how they will be oriented, and what velocity they will have over the next second or so.
Configuring the Trajectory Generator
The Trajectory Generator acts as a bridge between your CharacterMovementComponent and the MotionMatching database. It samples the current state and projects it into the future.
If a player is running forward and suddenly presses "Left," the trajectory generator creates a series of points (samples) in a curved path. Instead of forcing an instant turn, the system uses these points to search the database for an animation that includes a natural, high-quality turn.
To configure this in your Animation Blueprint, you typically work within an Animation Data Asset or a specific Trajectory Controller node. You define:
- Prediction Time: How far ahead in seconds to look (e.g., 0.5s to 1.0s).
- Sample Count: How many discrete points are stored along that path.
Here is how the logic flow looks conceptually in your movement update:
// Pseudocode for updating the Trajectory Data
Trajectory.Velocity = CurrentVelocity;
Trajectory.Rotation = CurrentRotation;
Trajectory.DesiredInput = GetLastInputVector();
// Predict the path based on inertia and input
PredictFuturePath(Trajectory, PredictionTime, SampleCount);
The Role of Input
If you rely only on Velocity, the character will feel sluggish because the animation won't anticipate turns. By including User Input (like the MoveForward and MoveRight axes) in your prediction logic, you provide the system with "intent." When you tilt the stick, the trajectory curves instantly, allowing the Motion Matching system to select the perfect "start of turn" animation frame before the character has even fully changed their physical direction.
Key Takeaway: Trajectory prediction transforms raw player input into a visual path, allowing the Motion Matching system to preemptively select the most natural animation for the character's intended movement.