Before You Begin

BLine supplies the path editor and path-following logic. Your robot code still owns localization and drivetrain control. Get those foundations working before trying to tune BLine.

What BLine provides

BLine has two current components:

Component	Job
BLine Web	Create, organize, simulate, and export paths in a browser or desktop app.
BLine-Lib	Load those paths on the robot and calculate robot-relative ChassisSpeeds from the robot's live pose.

BLine-Lib follows geometric path progress rather than a precomputed clock. It does not estimate the robot pose, tune individual swerve modules, avoid obstacles, or prove that a path is physically achievable.

Robot prerequisites

You should already have:

• a holonomic drivetrain, such as swerve or mecanum;
• a reliable Supplier<Pose2d>;
• a supplier for current robot-relative ChassisSpeeds;
• a consumer that accepts robot-relative ChassisSpeeds;
• working WPILib command-based code;
• stable steering and velocity control for the individual drivetrain modules; and
• drivetrain logging that lets you compare requested motion with measured motion.

A path follower cannot compensate for an incorrect wheel radius, gear ratio, coordinate frame, gyro sign, or unstable module controller. Verify those pieces with ordinary drivetrain commands first.

Choose a localization starting point

Localization answers where is the robot? BLine answers how should it move from that pose toward the path? BLine can use a pose produced by wheel odometry alone or by a pose estimator that also accepts vision measurements.

Robot capability	Practical guidance
Wheel and gyro odometry only	Reasonable for a short, simple autonomous routine when the robot starts accurately and wheel slip is limited. Begin with lower velocity and acceleration, verify straight paths first, and introduce faster, turn-heavy, or multi-segment motion incrementally.
Vision-corrected localization	Strongly recommended for longer routines, repeated direction changes, higher acceleration, recovery after contact, and other movement where odometry drift can accumulate.
Vision still being developed	Do not block the first BLine test on a camera pipeline. Prove a simple path with odometry, keep the motion envelope conservative, and add complexity only as the estimated pose proves repeatable.

Vision improves the pose supplied to BLine; it does not repair poor module calibration or excessive wheel slip. Even a vision-equipped robot should validate its odometry and gyro first.

Vocabulary used in this guide

Term	Meaning
Pose	Field position (x, y) plus robot heading.
Localization	Producing the live pose supplied to BLine. This may combine wheel odometry, a gyro, and vision.
Path	The geometric elements, constraints, rotations, and events BLine should follow.
Path following	Calculating drivetrain commands from the live pose and path state.
Trajectory	A path with desired states assigned to time. BLine does not follow a time-indexed trajectory.
Pathfinding	Choosing a route around obstacles. BLine can follow a route, but does not currently find one for you.

Read How BLine Works for a fuller comparison of geometric and time-parameterized tracking.

Choose an editor

Use	Best choice
Try BLine or edit from any laptop	Hosted BLine Web
Work directly in a robot repository	BLine Web desktop app
Generate a dynamic path entirely in Java	BLine-Lib without the editor

Browser workspaces are stored by the browser. Pressing Save does not write into your robot repository; export the autos folder when you are ready. The desktop app can work directly in an autos folder.

Prepare a safe test area

FRC robots can change speed or direction suddenly while tuning autonomous code.

• Use a controlled test area with physical barriers and no people inside it.
• Keep a functioning Driver Station connected and be ready to disable.
• Announce before enabling and confirm the Robot Signal Light is visible.
• Begin with the slow straight path in the next tutorial.
• Verify pose, coordinate frames, direction, and stopping behavior before tuning at the robot's intended motion limits.
• For most swerve paths, pre-orient the modules before testing, either in code or manually. Prioritize this when a path starts aggressively or must clear a nearby obstacle precisely; a gentle, repeatedly tested start may not need a separate orientation step.

Recommended learning path

1. Install the editor and library.
2. Create and run one simple path.
3. Learn the three controllers and tune the robot.
4. Learn path elements and constraints.
5. Add collections, linked elements, events, and advanced library features only after the basic path is repeatable.