2 #include <msp/core/algorithm.h>
3 #include <msp/game/transform.h>
4 #include "physicalentity.h"
9 Physics::Physics(Game::Stage &s):
11 event_source(stage.get_event_bus()),
12 observer(stage.get_event_bus())
14 observer.observe<Game::Events::EntityCreated>([this](auto &e){ entity_added(e); });
15 observer.observe<Game::Events::EntityDestroyed>([this](auto &e){ entity_removed(e); });
17 stage.synthesize_initial_events(observer);
20 void Physics::entity_added(const Game::Events::EntityCreated &e)
22 if(Game::Handle<PhysicalEntity> physical = dynamic_handle_cast<PhysicalEntity>(e.entity))
24 for(Game::Handle<Game::Entity> p=e.entity->get_parent(); p; p=p->get_parent())
25 if(p->get_transform())
28 SimulatedEntity sim_body;
29 sim_body.entity = physical;
30 if(physical->is_fixture())
32 entities.insert(entities.begin()+fixture_count, sim_body);
36 entities.push_back(sim_body);
40 void Physics::entity_removed(const Game::Events::EntityDestroyed &e)
42 if(Game::Handle<PhysicalEntity> physical = dynamic_handle_cast<PhysicalEntity>(e.entity))
44 auto i = find_member(entities, physical, &SimulatedEntity::entity);
47 size_t index = distance(entities.begin(), i);
48 if(index<fixture_count)
50 if(index+1!=fixture_count)
51 *i = std::move(entities[fixture_count-1]);
52 entities[fixture_count-1] = std::move(entities.back());
55 *i = std::move(entities.back());
61 void Physics::tick(Time::TimeDelta dt)
63 float dt_secs = dt/Time::sec;
65 for(unsigned i=0; i<fixture_count; ++i)
66 copy_in<true>(entities[i]);
67 for(unsigned i=fixture_count; i<entities.size(); ++i)
68 copy_in<false>(entities[i]);
73 for(unsigned i=0; i<10; ++i)
81 for(unsigned i=0; i<fixture_count; ++i)
82 copy_out<true>(entities[i]);
83 for(unsigned i=fixture_count; i<entities.size(); ++i)
84 copy_out<false>(entities[i]);
86 for(const Collision &c: collisions)
87 event_source.emit<Events::Collision>(entities[c.body1].entity->get_collider(), entities[c.body2].entity->get_collider());
90 template<bool is_fixture>
91 void Physics::copy_in(SimulatedEntity &entity)
93 Game::Handle<Game::Transform> transform = entity.entity->get_transform();
94 entity.position = transform->get_position().slice<2>(0);
95 const Geometry::Quaternion<float> &r = transform->get_rotation();
96 entity.rotation = Geometry::atan2<float>(2*(r.a*r.d+r.b*r.c), 1-2*(r.c*r.c+r.d*r.d));
98 if constexpr(is_fixture)
100 entity.inverse_mass = 0.0f;
101 entity.inverse_momi = 0.0f;
105 Game::Handle<RigidBody> body = entity.entity->get_body();
106 entity.inverse_mass = 1.0f/body->get_mass();
107 entity.inverse_momi = 1.0f/body->get_moment_of_inertia();
108 entity.external_force = body->get_force();
109 entity.external_torque = body->get_torque();
110 entity.velocity = body->get_velocity();
111 entity.angular_velocity = body->get_angular_velocity();
115 template<bool is_fixture>
116 void Physics::copy_out(SimulatedEntity &entity)
118 Game::Handle<Game::Transform> transform = entity.entity->get_transform();
119 transform->set_position(compose(entity.position, 0.0f));
120 transform->set_rotation(Geometry::Quaternion<float>::rotation(entity.rotation, LinAl::Vector<float, 3>(0, 0, 1)));
122 if constexpr(!is_fixture)
124 Game::Handle<RigidBody> body = entity.entity->get_body();
125 body->set_velocity(entity.velocity);
126 body->set_angular_velocity(entity.angular_velocity);
127 body->clear_forces();
131 void Physics::step(float dt_secs)
133 for(unsigned i=fixture_count; i<entities.size(); ++i)
135 SimulatedEntity &entity = entities[i];
137 LinAl::Vector<float, 2> new_velocity = entity.velocity+entity.external_force*(dt_secs*entity.inverse_mass);
138 entity.position += (entity.velocity+new_velocity)*(dt_secs/2);
139 entity.velocity = new_velocity;
141 Geometry::Angle<float> new_angular_velocity = entity.angular_velocity+Geometry::Angle<float>::from_radians(entity.external_torque*dt_secs*entity.inverse_momi);
142 entity.rotation = wrap_positive(entity.rotation+(entity.angular_velocity+new_angular_velocity)*(dt_secs/2));
143 entity.angular_velocity = new_angular_velocity;
147 void Physics::detect_collisions()
149 for(auto &c: collisions)
152 for(unsigned i=fixture_count; i<entities.size(); ++i)
154 Game::Handle<PhysicalEntity> entity1 = entities[i].entity;
155 ColliderType type1 = entity1->get_collider()->get_type();
156 for(unsigned j=0; j<i; ++j)
158 Game::Handle<PhysicalEntity> entity2 = entities[j].entity;
159 ColliderType type2 = entity2->get_collider()->get_type();
160 if(type1==ColliderType::CIRCLE && type2==ColliderType::CIRCLE)
161 collide_circle_circle(i, j);
162 else if(type1==ColliderType::CIRCLE && type2==ColliderType::BOX)
163 collide_circle_box(i, j);
164 else if(type1==ColliderType::BOX && type2==ColliderType::CIRCLE)
165 collide_circle_box(j, i);
170 void Physics::solve_collisions()
172 for(auto &e: entities)
174 e.position_adjust = LinAl::Vector<float, 2>();
175 e.collision_count = 0;
178 for(const auto &c: collisions)
183 SimulatedEntity &entity1 = entities[c.body1];
184 SimulatedEntity &entity2 = entities[c.body2];
185 float inv_mass_sum = 1.0f/(entity1.inverse_mass+entity2.inverse_mass);
186 LinAl::Vector<float, 2> delta = c.normal*c.depth*inv_mass_sum;
187 if(c.body1>=fixture_count)
189 entity1.position_adjust += delta*entity1.inverse_mass;
190 ++entity1.collision_count;
192 if(c.body2>=fixture_count)
194 entity2.position_adjust -= delta*entity1.inverse_mass;
195 ++entity2.collision_count;
199 for(auto &e: entities)
200 if(e.collision_count)
201 e.position += e.position_adjust/static_cast<float>(e.collision_count);
204 void Physics::apply_impulses()
206 for(const auto &c: collisions)
208 SimulatedEntity &entity1 = entities[c.body1];
209 SimulatedEntity &entity2 = entities[c.body2];
210 LinAl::Vector<float, 2> r1 = c.point-entity1.position;
211 LinAl::Vector<float, 2> r2 = c.point-entity2.position;
212 LinAl::Vector<float, 2> v_p1 = entity1.velocity+LinAl::Vector<float, 2>(-r1.y, r1.x)*entity1.angular_velocity.radians();
213 LinAl::Vector<float, 2> v_p2 = entity2.velocity+LinAl::Vector<float, 2>(-r2.y, r2.x)*entity2.angular_velocity.radians();
214 LinAl::Vector<float, 2> v_rel = v_p2-v_p1;
215 LinAl::Vector<float, 2> tangent = v_rel-c.normal*inner_product(v_rel, c.normal);
216 float v_tan = tangent.norm();
217 tangent = (v_tan>1e-5 ? normalize(tangent) : LinAl::Vector<float, 2>(-c.normal.y, c.normal.x));
218 float restitution = 1.0f;
219 float friction_coeff = 0.1f;
220 float inv_mass_sum = entity1.inverse_mass+entity2.inverse_mass;
221 float reaction = (1+restitution)*inner_product(v_rel, c.normal)/inv_mass_sum;
222 float friction = min(reaction*friction_coeff, v_tan/inv_mass_sum);
223 LinAl::Vector<float, 2> impulse = c.normal*reaction+tangent*friction;
224 entity1.velocity += impulse*entity1.inverse_mass;
225 entity2.velocity -= impulse*entity2.inverse_mass;
226 entity1.angular_velocity += Geometry::Angle<float>::from_radians(entity1.inverse_momi*(r1.x*impulse.y-r1.y*impulse.x));
227 entity2.angular_velocity -= Geometry::Angle<float>::from_radians(entity2.inverse_momi*(r2.x*impulse.y-r2.y*impulse.x));
231 Physics::Collision &Physics::get_collision(unsigned i, unsigned j)
233 for(auto &c: collisions)
234 if((c.body1==i && c.body2==j) || (c.body1==j && c.body2==i))
237 Collision &c = collisions.emplace_back();
243 void Physics::collide_circle_circle(unsigned i, unsigned j)
245 const LinAl::Vector<float, 2> &pos1 = entities[i].position;
246 const LinAl::Vector<float, 2> &pos2 = entities[j].position;
247 float r1 = entities[i].entity->get_collider()->get_radius();
248 float r2 = entities[j].entity->get_collider()->get_radius();
250 /* Points in the direction the first body needs to move in to clear the
252 LinAl::Vector<float, 2> delta = pos1-pos2;
253 float d_sq = inner_product(delta, delta);
257 Collision &collision = get_collision(i, j);
258 collision.normal = normalize(delta);
259 collision.depth = r1+r2-sqrt(d_sq);
260 collision.point = pos1-collision.normal*(r1-collision.depth/2);
261 if(collision.body1!=i)
262 collision.normal = -collision.normal;
266 void Physics::collide_circle_box(unsigned i, unsigned j)
268 const LinAl::Vector<float, 2> &pos1 = entities[i].position;
269 const LinAl::Vector<float, 2> &pos2 = entities[j].position;
270 float radius = entities[i].entity->get_collider()->get_radius();
271 LinAl::Vector<float, 2> half_size = entities[j].entity->get_collider()->get_size()/2.0f;
273 LinAl::Vector<float, 2> delta = pos1-pos2;
274 float c = cos(entities[j].rotation);
275 float s = sin(entities[j].rotation);
276 LinAl::Vector<float, 2> local_delta(c*delta.x+s*delta.y, c*delta.y-s*delta.x);
277 LinAl::Vector<float, 2> local_closest(clamp(local_delta.x, -half_size.x, half_size.x), clamp(local_delta.y, -half_size.y, half_size.y));
278 LinAl::Vector<float, 2> local_cdelta = local_delta-local_closest;
279 float d_sq = inner_product(local_cdelta, local_cdelta);
281 if(d_sq<radius*radius)
283 Collision &collision = get_collision(i, j);
286 collision.normal = normalize(LinAl::Vector<float, 2>(c*local_cdelta.x-s*local_cdelta.y, c*local_cdelta.y+s*local_cdelta.x));
287 collision.depth = radius-sqrt(d_sq);
291 LinAl::Vector<float, 2> inside_dist(half_size.x-abs(local_delta.x), half_size.y-abs(local_delta.y));
292 if(inside_dist.x<inside_dist.y)
294 collision.normal = LinAl::Vector<float, 2>(c, s) * (local_delta.x<0 ? -1.0f : 1.0f);
295 collision.depth = radius+inside_dist.x;
299 collision.normal = LinAl::Vector<float, 2>(-s, c) * (local_delta.y<0 ? -1.0f : 1.0f);
300 collision.depth = radius+inside_dist.y;
303 collision.point = pos1-collision.normal*(radius-collision.depth/2);
304 if(collision.body1!=i)
305 collision.normal = -collision.normal;