This PR updates the existing differentialdriveposeestimator example to include computer vision pose estimation and latency compensation.
The example generates a simulated cameraToTarget transformation, which is then fed into ComputerVisionUtil.objectToRobotPose() to compute the robot's field-relative position exclusively from vision measurements. The vision measurements are applied through DifferentialDrivePoseEstimator.addVisionMeasurement().
The updated example constructs an AprilTagFieldLayout from JSON. This requires a deploy directory, something which isn't currently supported in wpilibjExamples and wpilibcExamples.
This fixes the following compilation errors:
```
/home/tav/frc/wpilib/allwpilib/wpilibcExamples/src/main/cpp/examples/UnitTest/cpp/subsystems/Intake.cpp:5:10: fatal error: subsystems/Intake.h: No such file or directory
5 | #include "subsystems/Intake.h"
| ^~~~~~~~~~~~~~~~~~~~~
/home/tav/frc/wpilib/allwpilib/wpilibcExamples/src/test/cpp/examples/UnitTest/cpp/subsystems/IntakeTest.cpp:11:10: fatal error: Constants.h: No such file or directory
11 | #include "Constants.h"
| ^~~~~~~~~~~~~
```
This effectively replaces the Unscented Kalman Filter used for Pose Estimation with the Odometry model, and uses a recalculable Kalman gain matrix to update pose estimations whenever a vision measurement is added.
Notably, this change removes the need for the confusing generics used in Java, and the C++ implementation got quite a bit less complex as well.
Co-authored-by: Tyler Veness <calcmogul@gmail.com>
Refactor some examples to use newer features, such as HID factories, library-provided command factories, CommandPtr (C++), as well as new idioms such as static/instance command factories.
Motivation
Feedback from 2022 showed that the Trigger API is rather confusing, mostly due to the following:
- duplicate Trigger and Button APIs were available; users were confused searching for a nonexistent difference between them.
- the when terminology was ambiguous and unclear whether it refers to the high state or specifically the rising edge.
- the Active terminology didn't unambiguously refer to the high state; it wasn't unintuitive to understand it as "when the binding is active/polled".
- whileHeld vs whenHeld was very confusing, and the difference between them wasn't obvious. The parallel Trigger verbs, whileActiveContinuously and whileActiveOnce are much less confusing.
Solution
Deprecating Button and its binding methods. The rationale for deprecating Button (and not Trigger) is because Button uses terminology that is needlessly more specific and restricting to the button use case, making the use case of arbitrary trigger conditions unintuitive.
After consideration, deprecation of Button's subclasses was decided against:
- NetworkButton (a trigger condition based on a boolean NT entry/topic) is a use case that is not necessarily intuitive for teams to implement themselves, so it is an abstraction that should be provided in the library. A parallel class for the BooleanEvent level, NetworkBooleanEvent, was also added as part of NT4. NT listeners were considered as a alternative solution, but they require attention to thread safety, and aren't interoperable with the EventLoop API.
- JoystickButton/POVButton provide abstractions around HID buttons. The new Trigger-returning factories on the HID classes are an equal (if not more concise) alternative, but there is no reason not to keep them for those who find their use preferable.
At a later date in the deprecation cycle (perhaps for 2024), when Button is removed, these subclasses should be changed to inherit directly from Trigger.
Trigger's bindings are changed to use True/False terminology, as it should be unambiguous. Each binding type has both True and False variants; for brevity, only the True variants are listed here:
- onTrue (replaces whenActive): schedule on rising edge.
- whileTrue (replaces whileActiveOnce): schedule on rising edge, cancel on falling edge.
- toggleOnTrue (replaces toggleWhenActive): on rising edge, schedule if unscheduled and cancel if scheduled.
Two binding types are completely deprecated:
- cancelWhenActive: this is a fairly niche use case which is better described as having the trigger's rising edge (Trigger.rising()) as an end condition for the command (using Command.until()).
- whileActiveContinuously: however common, this relied on the no-op behavior of scheduling an already-scheduled command. The more correct way to repeat the command if it ends before the falling edge is using Command.repeatedly/RepeatCommand or a RunCommand -- the only difference is if the command is interrupted, but that is more likely to result in two commands perpetually canceling each other than achieve the desired behavior. Manually implementing a blindly-scheduling binding like whileActiveContinuously is still possible, though might not be intuitive.
Notes
It was considered to share BooleanEvent's digital signal terminology; however, once it was decided that Trigger should not inherit from BooleanEvent (due to overload incompatibility) the common terminology was not worth the unintuitiveness stemming from users' unfamiliarity with the signal processing terms.
All trigonometric functions and vector classes assume North-West-Up axes
convention, so using North-East-Down convention with them is really
error-prone. We've broken something every time we touched the drive
classes.
We originally used North-East-Down to match the joystick convention, but
the volume of long-lived bugs has made this not worth it in retrospect.
The rest of WPILib also uses North-West-Up, so this makes things
consistent.
KilloughDrive was removed since no one uses it.
