Action Builder and Trajectories

Build paths with the 1.0 builder model.

Road Runner 1.0 Actions and AutonomousRoad Runner

In this lesson, you will:

Use actionBuilder.
Choose simple path primitives.
Explain start and end poses.

Concept narrative

Road Runner action builders create drive actions from a start pose and a sequence of movement commands. The path should represent field strategy, not just cool-looking motion.

Robot mental model

A trajectory action is a field plan in code. The robot must start where the code thinks it starts, avoid obstacles, and end ready for the next mechanism action.

Implementation walkthrough

Start with line and strafe commands, then turns, then splines. Keep path complexity proportional to localization confidence.

ActionBuilder.javaJava

Action path = drive.actionBuilder(startPose)
    .lineToY(-36)
    .turn(Math.toRadians(-90))
    .strafeTo(new Vector2d(48, -36))
    .build();

Common mistakes and debugging

If a path starts wrong, check start pose first. If it clips field elements, simplify geometry before increasing constraints.

Practice

Build a park path two ways: simple lines and a spline. Compare risk and repeatability.

Checkpoint

Start pose is explicit.
Path shape matches strategy.
Simple version is tested first.
The test record includes the setup, prediction, and observed result.
A teammate can repeat the check from the saved evidence without guessing.

Reflection check

Check your understanding before moving on.

Why must an action builder start from the robot’s actual expected pose?

Every later trajectory segment is computed relative to that start pose.

The pose only affects dashboard colors.

It allows motor power greater than one.

When is it appropriate to add a spline to a Road Runner path?

Before the drive class is configured.

After simple line, strafe, and turn behavior is already validated.

Whenever a trajectory needs more Java methods.

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References

Road Runner 1.0 Builder ReferenceTrajectory/action builder method reference.Road Runner 1.0 ActionsAction composition, custom actions, and autonomous structure.