physics: add particle_force_generator

src/physics/particle_force_generator.cpp

@@ -29,4 +29,35 @@ namespace physics {
 
     particle->add_force(normalize(force) * drag_coeff);
   }
+
+  void particle_spring::update_force(particle * particle, float duration)
+  {
+    vec3 force = particle->position - other->position;
+
+    float intensity = abs<float>(magnitude(force) - rest_length) * spring_constant;
+
+    particle->add_force(normalize(force) * -intensity);
+  }
+
+  void particle_anchored_spring::update_force(particle * particle, float duration)
+  {
+    vec3 force = particle->position - *anchor;
+
+    float intensity = abs<float>(magnitude(force) - rest_length) * spring_constant;
+
+    particle->add_force(normalize(force) * -intensity);
+  }
+
+  void particle_bungee::update_force(particle * particle, float duration)
+  {
+    vec3 force = particle->position - other->position;
+
+    float _magnitude = magnitude(force);
+    if (_magnitude <= rest_length)
+      return;
+
+    float intensity = spring_constant * (rest_length - _magnitude);
+
+    particle->add_force(normalize(force) * -intensity);
+  }
 }

src/physics/particle_force_generator.hpp

@@ -44,4 +44,31 @@ namespace physics {
 
     void update_force(particle * particle, float duration) override;
   };
+
+  struct particle_spring : particle_force_generator
+  {
+    physics::particle * other;
+    float spring_constant;
+    float rest_length;
+
+    void update_force(particle * particle, float duration) override;
+  };
+
+  struct particle_anchored_spring : particle_force_generator
+  {
+    vec3 * anchor;
+    float spring_constant;
+    float rest_length;
+kk
+    void update_force(particle * particle, float duration) override;
+  };
+
+  struct particle_bungee : particle_force_generator
+  {
+    physics::particle * other;
+    float spring_constant;
+    float rest_length;
+
+    void update_force(particle * particle, float duration) override;
+  };
 }