Start experimenting with a generic joint implementation for joint drives.

src/dynamics/solver/joint_constraint/generic_position_constraint.rs

@@ -0,0 +1,171 @@
+use super::{GenericVelocityConstraint, GenericVelocityGroundConstraint};
+use crate::dynamics::{GenericJoint, IntegrationParameters, RigidBody};
+use crate::math::{
+    AngDim, AngVector, AngularInertia, Dim, Isometry, Point, Real, Rotation, SpatialVector, Vector,
+    DIM,
+};
+use crate::utils::{WAngularInertia, WCross};
+use na::{Vector3, Vector6};
+
+// FIXME: review this code for the case where the center of masses are not the origin.
+#[derive(Debug)]
+pub(crate) struct GenericPositionConstraint {
+    position1: usize,
+    position2: usize,
+    local_anchor1: Isometry<Real>,
+    local_anchor2: Isometry<Real>,
+    local_com1: Point<Real>,
+    local_com2: Point<Real>,
+    im1: Real,
+    im2: Real,
+    ii1: AngularInertia<Real>,
+    ii2: AngularInertia<Real>,
+
+    joint: GenericJoint,
+
+    lin_impulse: Cell<Vector3<Real>>,
+    ang_impulse: Cell<Vector3<Real>>,
+}
+
+impl GenericPositionConstraint {
+    pub fn from_params(rb1: &RigidBody, rb2: &RigidBody, joint: &GenericJoint) -> Self {
+        let ii1 = rb1.effective_world_inv_inertia_sqrt.squared();
+        let ii2 = rb2.effective_world_inv_inertia_sqrt.squared();
+        let im1 = rb1.effective_inv_mass;
+        let im2 = rb2.effective_inv_mass;
+
+        Self {
+            local_anchor1: joint.local_anchor1,
+            local_anchor2: joint.local_anchor2,
+            position1: rb1.active_set_offset,
+            position2: rb2.active_set_offset,
+            im1,
+            im2,
+            ii1,
+            ii2,
+            local_com1: rb1.mass_properties.local_com,
+            local_com2: rb2.mass_properties.local_com,
+            joint: *joint,
+        }
+    }
+
+    pub fn solve(&self, params: &IntegrationParameters, positions: &mut [Isometry<Real>]) {
+        let mut position1 = positions[self.position1 as usize];
+        let mut position2 = positions[self.position2 as usize];
+
+        let anchor1 = position1 * self.local_anchor1;
+        let anchor2 = position2 * self.local_anchor2;
+        let r1 = Point::from(anchor1.translation.vector) - position1 * self.local_com1;
+        let r2 = Point::from(anchor2.translation.vector) - position2 * self.local_com2;
+
+        let delta_pos = anchor1.inverse() * anchor2;
+        let mass_matrix = GenericVelocityConstraint::compute_mass_matrix(
+            &self.joint,
+            self.im1,
+            self.im2,
+            self.ii1,
+            self.ii2,
+            r1,
+            r2,
+            false,
+        );
+
+        let lin_err = delta_pos.translation.vector * params.joint_erp;
+        let ang_err = delta_pos.rotation.scaled_axis() * params.joint_erp;
+        let err = Vector6::new(
+            lin_err.x, lin_err.y, lin_err.z, ang_err.x, ang_err.y, ang_err.z,
+        );
+        let impulse = mass_matrix * err;
+        let lin_impulse = impulse.xyz();
+        let ang_impulse = Vector3::new(impulse[3], impulse[4], impulse[5]);
+
+        position1.rotation = Rotation::new(
+            self.ii1
+                .transform_vector(ang_impulse + r1.gcross(lin_impulse)),
+        ) * position1.rotation;
+        position2.rotation = Rotation::new(
+            self.ii2
+                .transform_vector(-ang_impulse - r2.gcross(lin_impulse)),
+        ) * position2.rotation;
+
+        position1.translation.vector += self.im1 * lin_impulse;
+        position2.translation.vector -= self.im2 * lin_impulse;
+
+        positions[self.position1 as usize] = position1;
+        positions[self.position2 as usize] = position2;
+    }
+}
+
+#[derive(Debug)]
+pub(crate) struct GenericPositionGroundConstraint {
+    position2: usize,
+    anchor1: Isometry<Real>,
+    local_anchor2: Isometry<Real>,
+    local_com2: Point<Real>,
+    im2: Real,
+    ii2: AngularInertia<Real>,
+    joint: GenericJoint,
+}
+
+impl GenericPositionGroundConstraint {
+    pub fn from_params(
+        rb1: &RigidBody,
+        rb2: &RigidBody,
+        joint: &GenericJoint,
+        flipped: bool,
+    ) -> Self {
+        let anchor1;
+        let local_anchor2;
+
+        if flipped {
+            anchor1 = rb1.predicted_position * joint.local_anchor2;
+            local_anchor2 = joint.local_anchor1;
+        } else {
+            anchor1 = rb1.predicted_position * joint.local_anchor1;
+            local_anchor2 = joint.local_anchor2;
+        };
+
+        Self {
+            anchor1,
+            local_anchor2,
+            position2: rb2.active_set_offset,
+            im2: rb2.effective_inv_mass,
+            ii2: rb2.effective_world_inv_inertia_sqrt.squared(),
+            local_com2: rb2.mass_properties.local_com,
+            joint: *joint,
+        }
+    }
+
+    pub fn solve(&self, params: &IntegrationParameters, positions: &mut [Isometry<Real>]) {
+        let mut position2 = positions[self.position2 as usize];
+
+        let anchor2 = position2 * self.local_anchor2;
+        let r2 = Point::from(anchor2.translation.vector) - position2 * self.local_com2;
+
+        let delta_pos = self.anchor1.inverse() * anchor2;
+        let mass_matrix = GenericVelocityGroundConstraint::compute_mass_matrix(
+            &self.joint,
+            self.im2,
+            self.ii2,
+            r2,
+            false,
+        );
+
+        let lin_err = delta_pos.translation.vector * params.joint_erp;
+        let ang_err = Vector3::zeros(); // delta_pos.rotation.scaled_axis() * params.joint_erp;
+        let err = Vector6::new(
+            lin_err.x, lin_err.y, lin_err.z, ang_err.x, ang_err.y, ang_err.z,
+        );
+        let impulse = mass_matrix * err;
+        let lin_impulse = impulse.xyz();
+        let ang_impulse = Vector3::new(impulse[3], impulse[4], impulse[5]);
+
+        position2.rotation = Rotation::new(
+            self.ii2
+                .transform_vector(-ang_impulse - r2.gcross(lin_impulse)),
+        ) * position2.rotation;
+        position2.translation.vector -= self.im2 * lin_impulse;
+
+        positions[self.position2 as usize] = position2;
+    }
+}