Pathfinder

This is 604's modified version of JacisNonsense's Pathfinder. The major modifications are

• PID followers continue calculating after the robot reaches the end
• The tank modifier retimes trajectories so that velocity limits are respected

The original README is below:.

---

Cross-Platform, Multi-Use Motion Profiling and Trajectory Generation.

Pathfinder is a library for generating Motion Profiles, a way to smoothly fit and follow a trajectory based upon given waypoints. Currently, both a C and Java API are available, but can be applied to almost any application.

An example profile is given below, with the waypoints:

1. X = -4, Y = -1, Angle = -45 degrees
2. X = -2, Y = -2, Angle = 0
3. X = 0, Y = 0, Angle = 0

The Graph on top is the X/Y position, and the Graph on the bottom is the Velocity.

Modifiers

Pathfinder supports Modifiers. Modifiers are a way to manipulate a trajectory with a given rule.
Pathfinder supports Tank and Swerve Drive modifiers.

Tank Drive:

Swerve Drive:

Part of the FIRST Robotics Competition?

Add the following lines to your build.gradle if you're using GradleRIO (2018.01.11 or higher):

Java:

dependencies {
    compile pathfinder()
}

C++:

model {
    frcUserProgram(NativeExecutableSpec) {
        lib library: "pathfinder"
    }
}

If you're not using GradleRIO, do the following:

Java

If you're not using GradleRIO, you must download this manually and copy into ~/wpilib/user/java/lib: http://dev.imjac.in/maven/jaci/pathfinder/Pathfinder-Java/1.8/Pathfinder-Java-1.8.jar
You also have to download this, extract it, and place libpathfinder.so into ~/wpilib/user/java/lib: http://dev.imjac.in/maven/jaci/pathfinder/Pathfinder-JNI/1.8/Pathfinder-JNI-1.8-athena.zip

C++

Download this and put libpathfinder.a in ~/wpilib/user/cpp/lib: http://dev.imjac.in/maven/jaci/pathfinder/Pathfinder-Core/1.8/Pathfinder-Core-1.8-athena.zip
Download this and extract all of its contents to ~/wpilib/user/cpp/include: http://dev.imjac.in/maven/jaci/pathfinder/Pathfinder-Core/1.8/Pathfinder-Core-1.8-headers.zip

Building / Installing on your Architecture

If you want to use Pathfinder on your system, you will have to build the library for your platform. You can do this with the following:

./gradlew build

The native libraries will be located under ./Pathfinder-Core/build/libs/pathfinder/ (shared and static libs, platform=any64) and ./Pathfinder-Java/build/libs/pathfinderjava/shared/any64. If you're using native shared (or java), you must put these somewhere on your system load path (e.g. Mac/Linux = /usr/local, Windows = Somwhere on PATH)

Usage

To see the usage for each language variation of the API, see the README in their folder.

Language	Folder
C	Pathfinder-Core
Java	Pathfinder-Java
LabVIEW	Pathfinder-LabVIEW

Other languages

The RobotPy project has created python bindings around the Pathfinder libraries, and can be found at https://github.com/robotpy/robotpy-pathfinder

A word on releases

The releases on Maven (mentioned above) are built for the NI RoboRIO (v16/7 2018 image). If you go to the github releases, you can download the 1.5 version for Windows/Linux/Mac releases.

Further reading

If you want to know more about how Pathfinder works, I highly suggest watching the seminar on Motion Profiling by FRC Team 254, which inspired and provided a lot of guidance for this project. Both use the same generation procedure, with some logistical differences.