3 #include <msp/game/transform.h>
4 #include "physicalentity.h"
9 Physics::Physics(Game::Stage &s):
11 observer(stage.get_event_bus())
13 observer.observe<Game::Events::EntityCreated>([this](auto &e){ entity_added(e); });
15 stage.synthesize_initial_events(observer);
18 void Physics::entity_added(const Game::Events::EntityCreated &e)
20 if(Game::Handle<PhysicalEntity> physical = dynamic_handle_cast<PhysicalEntity>(e.entity))
22 for(Game::Handle<Game::Entity> p=e.entity->get_parent(); p; p=p->get_parent())
23 if(p->get_transform())
26 SimulatedEntity sim_body;
27 sim_body.entity = physical;
28 if(physical->is_fixture())
30 entities.insert(entities.begin()+fixture_count, sim_body);
34 entities.push_back(sim_body);
38 void Physics::tick(Time::TimeDelta dt)
40 float dt_secs = dt/Time::sec;
42 for(unsigned i=0; i<fixture_count; ++i)
43 copy_in<true>(entities[i]);
44 for(unsigned i=fixture_count; i<entities.size(); ++i)
45 copy_in<false>(entities[i]);
50 for(unsigned i=0; i<10; ++i)
58 for(unsigned i=0; i<fixture_count; ++i)
59 copy_out<true>(entities[i]);
60 for(unsigned i=fixture_count; i<entities.size(); ++i)
61 copy_out<false>(entities[i]);
64 template<bool is_fixture>
65 void Physics::copy_in(SimulatedEntity &entity)
67 Game::Handle<Game::Transform> transform = entity.entity->get_transform();
68 entity.position = transform->get_position().slice<2>(0);
69 const Geometry::Quaternion<float> &r = transform->get_rotation();
70 entity.rotation = Geometry::atan2<float>(2*(r.a*r.d+r.b*r.c), 1-2*(r.c*r.c+r.d*r.d));
72 if constexpr(is_fixture)
74 entity.inverse_mass = 0.0f;
75 entity.inverse_momi = 0.0f;
79 Game::Handle<RigidBody> body = entity.entity->get_body();
80 entity.inverse_mass = 1.0f/body->get_mass();
81 entity.inverse_momi = 1.0f/body->get_moment_of_inertia();
82 entity.external_force = body->get_force();
83 entity.external_torque = body->get_torque();
84 entity.velocity = body->get_velocity();
85 entity.angular_velocity = body->get_angular_velocity();
89 template<bool is_fixture>
90 void Physics::copy_out(SimulatedEntity &entity)
92 Game::Handle<Game::Transform> transform = entity.entity->get_transform();
93 transform->set_position(compose(entity.position, 0.0f));
94 transform->set_rotation(Geometry::Quaternion<float>::rotation(entity.rotation, LinAl::Vector<float, 3>(0, 0, 1)));
96 if constexpr(!is_fixture)
98 Game::Handle<RigidBody> body = entity.entity->get_body();
99 body->set_velocity(entity.velocity);
100 body->set_angular_velocity(entity.angular_velocity);
101 body->clear_forces();
105 void Physics::step(float dt_secs)
107 for(unsigned i=fixture_count; i<entities.size(); ++i)
109 SimulatedEntity &entity = entities[i];
111 LinAl::Vector<float, 2> new_velocity = entity.velocity+entity.external_force*(dt_secs*entity.inverse_mass);
112 entity.position += (entity.velocity+new_velocity)*(dt_secs/2);
113 entity.velocity = new_velocity;
115 Geometry::Angle<float> new_angular_velocity = entity.angular_velocity+Geometry::Angle<float>::from_radians(entity.external_torque*dt_secs*entity.inverse_momi);
116 entity.rotation = wrap_positive(entity.rotation+(entity.angular_velocity+new_angular_velocity)*(dt_secs/2));
117 entity.angular_velocity = new_angular_velocity;
121 void Physics::detect_collisions()
123 for(auto &c: collisions)
126 for(unsigned i=fixture_count; i<entities.size(); ++i)
128 Game::Handle<PhysicalEntity> entity1 = entities[i].entity;
129 ColliderType type1 = entity1->get_collider()->get_type();
130 for(unsigned j=0; j<i; ++j)
132 Game::Handle<PhysicalEntity> entity2 = entities[j].entity;
133 ColliderType type2 = entity2->get_collider()->get_type();
134 if(type1==ColliderType::CIRCLE && type2==ColliderType::CIRCLE)
135 collide_circle_circle(i, j);
136 else if(type1==ColliderType::CIRCLE && type2==ColliderType::BOX)
137 collide_circle_box(i, j);
138 else if(type1==ColliderType::BOX && type2==ColliderType::CIRCLE)
139 collide_circle_box(j, i);
144 void Physics::solve_collisions()
146 for(auto &e: entities)
148 e.position_adjust = LinAl::Vector<float, 2>();
149 e.collision_count = 0;
152 for(const auto &c: collisions)
157 SimulatedEntity &entity1 = entities[c.body1];
158 SimulatedEntity &entity2 = entities[c.body2];
159 float inv_mass_sum = 1.0f/(entity1.inverse_mass+entity2.inverse_mass);
160 LinAl::Vector<float, 2> delta = c.normal*c.depth*inv_mass_sum;
161 if(c.body1>=fixture_count)
163 entity1.position_adjust += delta*entity1.inverse_mass;
164 ++entity1.collision_count;
166 if(c.body2>=fixture_count)
168 entity2.position_adjust -= delta*entity1.inverse_mass;
169 ++entity2.collision_count;
173 for(auto &e: entities)
174 if(e.collision_count)
175 e.position += e.position_adjust/static_cast<float>(e.collision_count);
178 void Physics::apply_impulses()
180 for(const auto &c: collisions)
182 SimulatedEntity &entity1 = entities[c.body1];
183 SimulatedEntity &entity2 = entities[c.body2];
184 LinAl::Vector<float, 2> r1 = c.point-entity1.position;
185 LinAl::Vector<float, 2> r2 = c.point-entity2.position;
186 LinAl::Vector<float, 2> v_p1 = entity1.velocity+LinAl::Vector<float, 2>(-r1.y, r1.x)*entity1.angular_velocity.radians();
187 LinAl::Vector<float, 2> v_p2 = entity2.velocity+LinAl::Vector<float, 2>(-r2.y, r2.x)*entity2.angular_velocity.radians();
188 LinAl::Vector<float, 2> v_rel = v_p2-v_p1;
189 LinAl::Vector<float, 2> tangent = v_rel-c.normal*inner_product(v_rel, c.normal);
190 float v_tan = tangent.norm();
191 tangent = (v_tan>1e-5 ? normalize(tangent) : LinAl::Vector<float, 2>(-c.normal.y, c.normal.x));
192 float restitution = 1.0f;
193 float friction_coeff = 0.1f;
194 float inv_mass_sum = entity1.inverse_mass+entity2.inverse_mass;
195 float reaction = (1+restitution)*inner_product(v_rel, c.normal)/inv_mass_sum;
196 float friction = min(reaction*friction_coeff, v_tan/inv_mass_sum);
197 LinAl::Vector<float, 2> impulse = c.normal*reaction+tangent*friction;
198 entity1.velocity += impulse*entity1.inverse_mass;
199 entity2.velocity -= impulse*entity2.inverse_mass;
200 entity1.angular_velocity += Geometry::Angle<float>::from_radians(entity1.inverse_momi*(r1.x*impulse.y-r1.y*impulse.x));
201 entity2.angular_velocity -= Geometry::Angle<float>::from_radians(entity2.inverse_momi*(r2.x*impulse.y-r2.y*impulse.x));
205 Physics::Collision &Physics::get_collision(unsigned i, unsigned j)
207 for(auto &c: collisions)
208 if((c.body1==i && c.body2==j) || (c.body1==j && c.body2==i))
211 Collision &c = collisions.emplace_back();
217 void Physics::collide_circle_circle(unsigned i, unsigned j)
219 const LinAl::Vector<float, 2> &pos1 = entities[i].position;
220 const LinAl::Vector<float, 2> &pos2 = entities[j].position;
221 float r1 = entities[i].entity->get_collider()->get_radius();
222 float r2 = entities[j].entity->get_collider()->get_radius();
224 /* Points in the direction the first body needs to move in to clear the
226 LinAl::Vector<float, 2> delta = pos1-pos2;
227 float d_sq = inner_product(delta, delta);
231 Collision &collision = get_collision(i, j);
232 collision.normal = normalize(delta);
233 collision.depth = r1+r2-sqrt(d_sq);
234 collision.point = pos1-collision.normal*(r1-collision.depth/2);
235 if(collision.body1!=i)
236 collision.normal = -collision.normal;
240 void Physics::collide_circle_box(unsigned i, unsigned j)
242 const LinAl::Vector<float, 2> &pos1 = entities[i].position;
243 const LinAl::Vector<float, 2> &pos2 = entities[j].position;
244 float radius = entities[i].entity->get_collider()->get_radius();
245 LinAl::Vector<float, 2> half_size = entities[j].entity->get_collider()->get_size()/2.0f;
247 LinAl::Vector<float, 2> delta = pos1-pos2;
248 float c = cos(entities[j].rotation);
249 float s = sin(entities[j].rotation);
250 LinAl::Vector<float, 2> local_delta(c*delta.x+s*delta.y, c*delta.y-s*delta.x);
251 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));
252 LinAl::Vector<float, 2> local_cdelta = local_delta-local_closest;
253 float d_sq = inner_product(local_cdelta, local_cdelta);
255 if(d_sq<radius*radius)
257 Collision &collision = get_collision(i, j);
260 collision.normal = normalize(LinAl::Vector<float, 2>(c*local_cdelta.x-s*local_cdelta.y, c*local_cdelta.y+s*local_cdelta.x));
261 collision.depth = radius-sqrt(d_sq);
265 LinAl::Vector<float, 2> inside_dist(half_size.x-abs(local_delta.x), half_size.y-abs(local_delta.y));
266 if(inside_dist.x<inside_dist.y)
268 collision.normal = LinAl::Vector<float, 2>(c, s) * (local_delta.x<0 ? -1.0f : 1.0f);
269 collision.depth = radius+inside_dist.x;
273 collision.normal = LinAl::Vector<float, 2>(-s, c) * (local_delta.y<0 ? -1.0f : 1.0f);
274 collision.depth = radius+inside_dist.y;
277 collision.point = pos1-collision.normal*(radius-collision.depth/2);
278 if(collision.body1!=i)
279 collision.normal = -collision.normal;