void physics_step(DB& db, double timeStep) {
using std::get;
using components::Velocity;
using components::BoundingBox;
using components::Solid;
using components::NoCollide;
using Ginseng::Not;
auto gravity = 1500.0;
auto bb_vels = db.query<BoundingBox, Velocity, Not<NoCollide>>();
auto bbs = db.query<BoundingBox, Not<NoCollide>>();
for (auto ent : db.query<CollisionData>()) {
db.eraseComponent(get<1>(ent).id());
}
for (auto ent_v : bb_vels) {
Velocity &v_vel = get<2>(ent_v).data();
v_vel.acc.y += gravity;
for (auto& p : v_vel.timed_accs) {
double t = std::min(p.second,timeStep);
p.second -= t;
v_vel.acc += p.first * float(t/timeStep);
}
v_vel.timed_accs.erase(std::remove_if(v_vel.timed_accs.begin(), v_vel.timed_accs.end(), [](auto& p){return p.second<=0;}), v_vel.timed_accs.end());
}
auto do_axis = [&](auto get_axis) {
for (auto ent_v : bb_vels) //search entities with velocities
{
EntID v_eid = get<0>(ent_v);
BoundingBox &v_bb = get<1>(ent_v).data();
Velocity &v_vel = get<2>(ent_v).data();
get_axis(v_vel.vel) += get_axis(v_vel.acc) * timeStep;
get_axis(v_bb.rect) += get_axis(v_vel.vel) * timeStep + 0.5 * get_axis(v_vel.acc) * timeStep * timeStep;
auto v_coll_info = v_eid.get<CollisionData>();
if (!v_coll_info) {
db.makeComponent(v_eid, CollisionData{});
v_coll_info = v_eid.get<CollisionData>();
}
for (auto ent_bb : bbs) //search entities with bounding boxes
{
EntID bb_eid = get<0>(ent_bb);
BoundingBox &bb = get<1>(ent_bb).data();
if (v_eid == bb_eid)
continue;
sf::FloatRect isect;
sf::FloatRect bbsmall (bb.rect.left, bb.rect.top, bb.rect.width-0.5, bb.rect.height-0.5);
if (v_bb.rect.intersects(bbsmall, isect)) {
if (bb_eid.get<Solid>()) {
if (get_axis(v_bb.rect) < get_axis(bb.rect)) {
get_axis(v_bb.rect) -= get_axis.len(isect);
} else {
get_axis(v_bb.rect) += get_axis.len(isect);
}
get_axis(v_vel.vel) = 0;
get_axis.other(v_vel.vel) -= float(get_axis.other(v_vel.vel)*5*timeStep); //friction
}
auto bb_coll_info = bb_eid.get<CollisionData>();
if (!bb_coll_info) {
db.makeComponent(bb_eid, CollisionData{});
bb_coll_info = bb_eid.get<CollisionData>();
}
auto hitdirs = get_axis.hitdirs(v_bb.rect, bb.rect);
v_coll_info.data().hits.push_back(CollisionData::Hit{bb_eid,hitdirs.first});
bb_coll_info.data().hits.push_back(CollisionData::Hit{v_eid,hitdirs.second});
}
}
get_axis(v_vel.acc) = 0;
}
};
do_axis(GetX{});
do_axis(GetY{});
}
