Spring Joint

The Spring Joint is a variant of the previous Six Degrees-of-Freedom joint that includes the addition of springs for each degree of freedom. Springs and motors cannot be combined in this constraint.

SpringJoint3D

In Evergine, a Spring Joint is implemented using the Generic6DoFJoint3D component.

Properties

Common Properties

Property	Default	Description
ConnectedEntityPath	null	The entity path of the connected body. Only when the path is valid is a joint established properly.
Anchor	0, 0, 0	The point that defines the center of the joint in source entity local space. All physics-based simulations use this point as the center in calculations.
AutoConfigureConnected	true	Enable this setting to automatically calculate the ConnectedAnchor position to match the global position of the anchor property. This is the default setting. Disable it to configure the position of the connected anchor manually.
ConnectedAnchor	auto-calculated	Manually configure the connected anchor position, in the connected body's local space.
BreakPoint	0	If the value is greater than 0, it indicates the force that needs to be applied for this joint to break.
CollideConnected	false	Determines whether a collision between the two bodies managed by the joint is enabled.

Limit Properties

The following properties set the limits of the object's movement.

Property	Default	Description
UseLinearLimit	false	If enabled, the position of the connected object will be restricted within the LowerAngularLimit & UpperAngularLimit values.
LowerLinearLimit	0	The lower distance of the limit.
UpperLinearLimit	0	The upper distance of the limit.
UseAngularLimit	false	If enabled, the angular rotations will be restricted within the LowerAngularLimit & UpperAngularLimit values.
LowerAngularLimit	0	The lowest angle the rotation can go.
UpperAngularLimit	0	The highest angle the rotation can go.

Spring Properties

The following properties set the spring functionality of this joint.

Property	Default	Description
UseSpringTranslationX, Y, Z	false	If enabled, apply the spring functionality on the X, Y, or Z axis respectively.
EquilibriumPointTranslationX, Y, Z	0	Sets the equilibrium point of the spring forces along the X, Y, or Z translation axis.
SpringStiffnessTranslationX, Y, Z	0	Sets the spring stiffness along the X, Y, or Z translation axis.
SpringDampingTranslationX, Y, Z	1	Sets the spring damping along the X, Y, or Z translation axis.
UseSpringRotationX, Y, Z	false	If enabled, apply the spring functionality on the X, Y, or Z axis respectively.
EquilibriumPointRotationX, Y, Z	0	Sets the equilibrium point of the spring forces along the X, Y, or Z rotation axis.
SpringStiffnessRotationX, Y, Z	0	Sets the spring stiffness along the X, Y, or Z rotation axis.
SpringDampingRotationX, Y, Z	1	Sets the spring damping along the X, Y, or Z rotation axis.

Using Spring Joint

This snippet uses a Spring Joint to add some spring functionality as demonstrated in the Generic6DoF Joint example.

protected override void CreateScene()
{
    this.Managers.RenderManager.DebugLines = true;

    // Load your material
    var material = this.Managers.AssetSceneManager.Load<Material>(DefaultResourcesIDs.DefaultMaterialID);
    var cubeMaterial = this.Managers.AssetSceneManager.Load<Material>(EvergineContent.CrateMat);

    float sliderLength = 3;

    // Create the slider holder...
    Entity slider = new Entity()
        .AddComponent(new Transform3D()
        {
            Scale = new Vector3(sliderLength, 0.1f, 0.1f),
            Rotation = new Vector3(0, 0, MathHelper.ToRadians(-45))   // Rotate the slider axis by 45º
        })
        .AddComponent(new MaterialComponent() { Material = material })
        .AddComponent(new CubeMesh())
        .AddComponent(new MeshRenderer())
        .AddComponent(new RigidBody3D()
        {
            PhysicBodyType = RigidBodyType3D.Kinematic
        });

    // Create the sliding object...
    Entity cube = new Entity()
        .AddComponent(new Transform3D())
        .AddComponent(new MaterialComponent() { Material = cubeMaterial })
        .AddComponent(new CubeMesh() { Size = 0.5f })
        .AddComponent(new MeshRenderer())
        .AddComponent(new RigidBody3D()
        {
            PhysicBodyType = RigidBodyType3D.Dynamic,
        });

    // Create the Joint
    slider.AddComponent(new SpringJoint3D()
    {
        ConnectedEntityPath = cube.EntityPath,

        UseLinearLimit = true,                  // Limit the slider
        LowerLinearLimit = new Vector3(0, 0, -sliderLength / 2),
        UpperLinearLimit = new Vector3(0, 0, sliderLength / 2),

        UseSpringTranslationZ = true,            // Add a linear spring on the Z axis
        EquilibriumPointTranslationZ = 0,
        SpringStiffnessTranslationZ = 10,
        SpringDampingTranslationZ = 0.02f,
    });

    this.Managers.EntityManager.Add(slider);
    this.Managers.EntityManager.Add(cube);
}