physics: add particle_link

src/physics/particle_link.cpp

@@ -0,0 +1,52 @@
+#include "particle_link.hpp"
+
+namespace physics {
+
+  float particle_link::current_length() const
+  {
+    vec3 relative_position = particle[0]->position - particle[1]->position;
+
+    return magnitude(relative_position);
+  }
+
+  int particle_cable::fill_contact(particle_contact * contact, int contact_length) const
+  {
+    float cur_length = current_length();
+    if (cur_length < max_length)
+      return 0;
+
+    contact->particle[0] = particle[0];
+    contact->particle[1] = particle[1];
+
+    vec3 normal = normalize(particle[1]->position - particle[0]->position);
+    contact->contact_normal = normal;
+    contact->penetration = cur_length - max_length;
+    contact->restitution = restitution;
+
+    return 1;
+  }
+
+  int particle_rod::fill_contact(particle_contact * contact, int contact_length) const
+  {
+    float cur_length = current_length();
+    if (cur_length == length)
+      return 0;
+
+    contact->particle[0] = particle[0];
+    contact->particle[1] = particle[1];
+
+    vec3 normal = normalize(particle[1]->position - particle[0]->position);
+
+    if (cur_length > length) {
+      contact->contact_normal = normal;
+      contact->penetration = cur_length - length;
+    } {
+      contact->contact_normal = -normal;
+      contact->penetration = length - cur_length;
+    }
+
+    contact->restitution = 0;
+
+    return 1;
+  }
+}

src/physics/particle_link.hpp

@@ -0,0 +1,33 @@
+#pragma once
+
+#include "particle.hpp"
+#include "particle_contact.hpp"
+
+namespace physics {
+
+  struct particle_link
+  {
+    physics::particle * particle[2];
+
+    float current_length() const;
+
+    virtual int fill_contact(particle_contact * contact, int contact_length) const = 0;
+  };
+
+  struct particle_cable : particle_link
+  {
+    float max_length;
+    float restitution;
+
+    int fill_contact(particle_contact * contact, int contact_length) const override;
+  };
+
+  struct particle_rod : particle_link
+  {
+    float length;
+
+    float current_length() const;
+
+    int fill_contact(particle_contact * contact, int contact_length) const override;
+  };
+}