1 files changed, 28 insertions, 0 deletions
diff --git a/physics/src/force/spring.rs b/physics/src/force/spring.rs
new file mode 100644
index 0000000..6c2cf67
--- /dev/null
+++ b/physics/src/force/spring.rs
@@ -0,0 +1,28 @@
+use crate::algebra::Scalar;
+
+use super::Force;
+
+pub struct Spring {
+    pub particle_ids: [usize; 2],
+    pub rest_length: Scalar,
+    pub spring_constant: Scalar,
+    pub damping_constant: Scalar,
+}
+
+impl Force for Spring {
+    fn apply(&self, particles: &mut Vec<crate::particle_system::Particle>) {
+        let a = &particles[self.particle_ids[0]];
+        let b = &particles[self.particle_ids[1]];
+        let i = a.position - b.position;
+        let i_dot = a.velocity - b.velocity;
+        let i_norm = i.norm();
+
+        let force = -(self.spring_constant * (i_norm - self.rest_length)
+        + (self.damping_constant * i.dot(&i_dot) / i_norm))
+        * i
+        / i_norm;
+
+        particles[self.particle_ids[0]].apply_force(force);
+        particles[self.particle_ids[1]].apply_force(-force);
+    }
+}