Hello RealityKit developers,
I'm currently working on physics simulations in my visionOS app and am trying to adapt the concepts from the official sample Simulating physics joints in your RealityKit app.
In the sample, a sphere is connected to the ceiling using a PhysicsRevoluteJoint to create a hinge-like simulation. I've successfully modified this setup to use a PhysicsSphericalJoint instead.
The basic replacement works as expected: pin1 (attached to the sphere) rotates freely around pin0 (attached to the ceiling), much like a ball-and-socket joint should, removing all translational degrees of freedom.
My challenge lies with the PhysicsSphericalJoint's angularLimitInYZ property. The documentation mentions that this property allows limiting the rotation around the Y and Z axes, defining an "elliptical cone shape around the x-axis of pin0." However, I'm struggling to understand how to specify these values to achieve a desired rotational limit.
If I have a sphere that is currently capable of rotating 360 degrees around pin0 (like a free-spinning ball on a string), how would I use angularLimitInYZ to restrict its rotation to a certain height or angular range, preventing it from completing a full circle?
Specifically, I'm trying to achieve a "swing" like behavior where the sphere oscillates back and forth but cannot rotate completely overhead or underfoot. What values or approach should I use for the angularLimitInYZ tuple to define such a restricted pendulum-like motion?
Any insights, code examples, or explanations on how to properly configure angularLimitInYZ for this kind of behavior would be incredibly helpful!
The following code is modified from the sample.
extension MainView {
func addPinsTo(ballEntity: Entity, attachmentEntity: Entity) throws {
let hingeOrientation = simd_quatf(from: [1, 0, 0], to: [0, 0, 1])
let attachmentPin = attachmentEntity.pins.set(
named: "attachment_hinge",
position: .zero,
orientation: hingeOrientation
)
let relativeJointLocation = attachmentEntity.position(
relativeTo: ballEntity
)
let ballPin = ballEntity.pins.set(
named: "ball_hinge",
position: relativeJointLocation,
orientation: hingeOrientation
)
// Create a PhysicsSphericalJoint between the two pins.
let revoluteJoint = PhysicsSphericalJoint(pin0: attachmentPin, pin1: ballPin)
try revoluteJoint.addToSimulation()
}
}
The following image is a screenshot of the operation when changing to PhysicsSphericalJoint.
Thank you in advance for your assistance.
