Fix #378 Added one example join_motor_position

examples2d/all_examples2.rs

@@ -16,6 +16,7 @@ mod convex_polygons2;
 mod damping2;
 mod debug_box_ball2;
 mod drum2;
+mod joint_motor_position2;
 mod heightfield2;
 mod joints2;
 mod locked_rotations2;
@@ -79,6 +80,7 @@ pub fn main() {
         ("Rope Joints", rope_joints2::init_world),
         ("Sensor", sensor2::init_world),
         ("Trimesh", trimesh2::init_world),
+        ("Joint motor position", joint_motor_position2::init_world),
         ("(Debug) box ball", debug_box_ball2::init_world),
     ];
 

examples2d/joint_motor_position2.rs

@@ -0,0 +1,46 @@
+use rapier2d::prelude::*;
+use rapier_testbed2d::Testbed;
+
+pub fn init_world(testbed: &mut Testbed) {
+    /*
+     * World
+     */
+    let mut bodies = RigidBodySet::new();
+    let mut colliders = ColliderSet::new();
+    let mut impulse_joints = ImpulseJointSet::new();
+    let multibody_joints = MultibodyJointSet::new();
+
+    /*
+     * The ground
+     */
+    let ground_size = 5.0;
+    let ground_height = 0.1;
+
+    let rigid_body = RigidBodyBuilder::fixed().translation(vector![0.0, -ground_height]);
+    let ground_handle = bodies.insert(rigid_body);
+    let collider = ColliderBuilder::cuboid(ground_size, ground_height);
+    colliders.insert_with_parent(collider, ground_handle, &mut bodies);
+
+    /*
+     * A rectangle on a motor
+     */
+    for num in 0..9 {
+        let x_pos = -6.0 + 1.5 * num as f32; 
+        let rigid_body = RigidBodyBuilder::dynamic().translation(vector![x_pos, 2.0]);
+        let handle = bodies.insert(rigid_body);
+        let collider = ColliderBuilder::cuboid(0.1, 0.5);
+        colliders.insert_with_parent(collider, handle, &mut bodies);
+
+        let joint = RevoluteJointBuilder::new()
+            .local_anchor2(point![x_pos, 1.5])
+            .local_anchor1(point![0.0, -0.5])
+            .motor_position(std::f32::consts::PI/4.0*num as f32, 100.0, 15.0);
+        impulse_joints.insert(handle,ground_handle, joint, true);
+    }
+
+    /*
+     * Set up the testbed.
+     */
+    testbed.set_world_with_params(bodies, colliders, impulse_joints, multibody_joints,vector![0.0,0.0],());
+    testbed.look_at(point![0.0, 0.0], 40.0);
+}

src/dynamics/solver/joint_constraint/joint_generic_velocity_constraint_builder.rs

@@ -12,6 +12,8 @@ use na::{DVector, SVector};
 
 #[cfg(feature = "dim3")]
 use crate::utils::WAngularInertia;
+#[cfg(feature = "dim2")]
+const PI: Real = std::f64::consts::PI as Real;
 
 impl SolverBody<Real, 1> {
     pub fn fill_jacobians(
@@ -413,12 +415,18 @@ impl JointVelocityConstraintBuilder<Real> {
         let mut rhs_wo_bias = 0.0;
         if motor_params.erp_inv_dt != 0.0 {
             #[cfg(feature = "dim2")]
-            let s_ang_dist = self.ang_err.im;
+            {
+                let s_ang_dist = self.ang_err.angle();
+                let s_target_ang = motor_params.target_pos;
+                rhs_wo_bias += ((s_ang_dist - s_target_ang) % (2.0*PI))/(2.0*PI) * motor_params.erp_inv_dt;
+            }
             #[cfg(feature = "dim3")]
+            {
                 let s_ang_dist = self.ang_err.imag()[_motor_axis];
                 let s_target_ang = motor_params.target_pos.sin();
                 rhs_wo_bias += (s_ang_dist - s_target_ang) * motor_params.erp_inv_dt;
             }
+        }
 
         let dvel = ang_jac.gdot(body2.angvel) - ang_jac.gdot(body1.angvel);
         rhs_wo_bias += dvel - motor_params.target_vel;
@@ -791,12 +799,18 @@ impl JointVelocityConstraintBuilder<Real> {
         let mut rhs = 0.0;
         if motor_params.erp_inv_dt != 0.0 {
             #[cfg(feature = "dim2")]
-            let s_ang_dist = self.ang_err.im;
+            {
+                let s_ang_dist = self.ang_err.angle();
+                let s_target_ang = motor_params.target_pos;
+                rhs += ((s_ang_dist - s_target_ang) % (2.0*PI))/(2.0*PI) * motor_params.erp_inv_dt;
+            }
             #[cfg(feature = "dim3")]
+            {
                 let s_ang_dist = self.ang_err.imag()[_motor_axis];
                 let s_target_ang = motor_params.target_pos.sin();
                 rhs += (s_ang_dist - s_target_ang) * motor_params.erp_inv_dt;
             }
+        }
 
         let dvel = ang_jac.gdot(body2.angvel) - ang_jac.gdot(body1.angvel);
         rhs += dvel - motor_params.target_vel;

src/dynamics/solver/joint_constraint/joint_velocity_constraint_builder.rs

@@ -354,13 +354,20 @@ impl<N: WReal> JointVelocityConstraintBuilder<N> {
         let mut rhs_wo_bias = N::zero();
         if motor_params.erp_inv_dt != N::zero() {
             #[cfg(feature = "dim2")]
-            let s_ang_dist = self.ang_err.im;
+            {
+                let s_ang_dist = self.ang_err.angle();
+                let s_target_ang = motor_params.target_pos;
+                rhs_wo_bias += ((s_ang_dist - s_target_ang) % N::simd_two_pi())/N::simd_two_pi() * motor_params.erp_inv_dt;
+            }
             #[cfg(feature = "dim3")]
+            {
                 let s_ang_dist = self.ang_err.imag()[_motor_axis];
                 let s_target_ang = motor_params.target_pos.simd_sin();
                 rhs_wo_bias += (s_ang_dist - s_target_ang) * motor_params.erp_inv_dt;
             }
            
+        }
+
         let dvel = ang_jac.gdot(body2.angvel) - ang_jac.gdot(body1.angvel);
         rhs_wo_bias += dvel - motor_params.target_vel;
 
@@ -795,12 +802,18 @@ impl<N: WReal> JointVelocityConstraintBuilder<N> {
         let mut rhs_wo_bias = N::zero();
         if motor_params.erp_inv_dt != N::zero() {
             #[cfg(feature = "dim2")]
-            let s_ang_dist = self.ang_err.im;
+            {
+                let s_ang_dist = self.ang_err.angle();
+                let s_target_ang = motor_params.target_pos;
+                rhs_wo_bias += ((s_ang_dist - s_target_ang) % N::simd_two_pi())/N::simd_two_pi() * motor_params.erp_inv_dt;
+            }
             #[cfg(feature = "dim3")]
+            {
                 let s_ang_dist = self.ang_err.imag()[_motor_axis];
                 let s_target_ang = motor_params.target_pos.simd_sin();
                 rhs_wo_bias += (s_ang_dist - s_target_ang) * motor_params.erp_inv_dt;
             }
+        }
 
         let dvel = ang_jac.gdot(body2.angvel) - ang_jac.gdot(body1.angvel);
         rhs_wo_bias += dvel - motor_params.target_vel;