Start experimenting with a generic joint implementation for joint drives.

src/dynamics/joint/generic_joint.rs

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+use crate::math::{Isometry, Real, SpacialVector, SPATIAL_DIM};
+
+#[derive(Copy, Clone, Debug)]
+#[cfg_attr(feature = "serde-serialize", derive(Serialize, Deserialize))]
+/// A joint that prevents all relative movement between two bodies.
+///
+/// Given two frames of references, this joint aims to ensure these frame always coincide in world-space.
+pub struct GenericJoint {
+    /// The frame of reference for the first body affected by this joint, expressed in the local frame
+    /// of the first body.
+    pub local_anchor1: Isometry<Real>,
+    /// The frame of reference for the second body affected by this joint, expressed in the local frame
+    /// of the first body.
+    pub local_anchor2: Isometry<Real>,
+    /// The impulse applied to the first body affected by this joint.
+    ///
+    /// The impulse applied to the second body affected by this joint is given by `-impulse`.
+    /// This combines both linear and angular impulses:
+    /// - In 2D, `impulse.xy()` gives the linear impulse, and `impulse.z` the angular impulse.
+    /// - In 3D, `impulse.xyz()` gives the linear impulse, and `(impulse[3], impulse[4], impulse[5])` the angular impulse.
+    pub impulse: SpacialVector<Real>,
+
+    pub min_position: SpacialVector<Real>,
+    pub max_position: SpacialVector<Real>,
+    pub target_velocity: SpacialVector<Real>,
+    /// The maximum negative impulse the joint can apply on each DoF. Must be <= 0.0
+    pub max_negative_impulse: SpacialVector<Real>,
+    /// The maximum positive impulse the joint can apply on each DoF. Must be >= 0.0
+    pub max_positive_impulse: SpacialVector<Real>,
+}
+
+impl GenericJoint {
+    /// Creates a new fixed joint from the frames of reference of both bodies.
+    pub fn new(local_anchor1: Isometry<Real>, local_anchor2: Isometry<Real>) -> Self {
+        Self {
+            local_anchor1,
+            local_anchor2,
+            impulse: SpacialVector::zeros(),
+            min_position: SpacialVector::zeros(),
+            max_position: SpacialVector::zeros(),
+            target_velocity: SpacialVector::zeros(),
+            max_negative_impulse: SpacialVector::repeat(-Real::MAX),
+            max_positive_impulse: SpacialVector::repeat(Real::MAX),
+        }
+    }
+}