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physics #90

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merged 6 commits into from
Apr 1, 2018
Merged

physics #90

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eabc613
physics
DragoonXen Mar 31, 2018
f8fc14c
fine tune collision power
DragoonXen Apr 1, 2018
4ba7f09
fix collision force calculation
DragoonXen Apr 1, 2018
f606590
minor collision fix
DragoonXen Apr 1, 2018
2229143
check if distance zero before collision calc
DragoonXen Apr 1, 2018
80a013f
fix id's retreiving for server build
DragoonXen Apr 1, 2018
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1 change: 1 addition & 0 deletions agario/local_runner/constants.h
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Original file line number Diff line number Diff line change
Expand Up @@ -116,6 +116,7 @@ const double VIS_SHIFT = 10.0; // dx = qCos(angle) * VS; dy = qSin(angle) * VS
const double DRAW_SPEED_FACTOR = 14.0;
//const double INERTION_FACTOR = 10.0;

const double COLLISION_POWER = 20.;
//const double SPEED_FACTOR = 25.0; // speed = SF / sqrt(mass)
//const double RADIUS_FACTOR = 2.0; // radius = RF * sqrt(mass)
const double MASS_EAT_FACTOR = 1.20; // mass > food.mass * MEF
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73 changes: 49 additions & 24 deletions agario/local_runner/entities/player.h
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Expand Up @@ -293,36 +293,61 @@ class Player : public Circle
return new_player;
}

double tangent_projection(Player *c1, Player *c2, double dist) {
if (dist > 0 && c1->speed > 0) {
double speed_x = c1->speed * qCos(c1->angle);
double speed_y = c1->speed * qSin(c1->angle);

double norm_x = -(c1->y - c2->y), norm_y = c1->x - c2->x;
double scalar = norm_x * speed_x + norm_y * speed_y;
double cos_beta = scalar / dist / c1->speed;
return qAcos(cos_beta);
}
return 0.0;
}

bool can_fuse(Player *frag) {
double dist = frag->calc_dist(x, y);
double nR = radius + frag->getR();

if (frag->fuse_timer > 0 && dist <= nR && !is_fast) {
double beta = tangent_projection(this, frag, dist);
if (qAbs(beta) < M_PI / 2) {
angle -= beta;
}
// speed *= qCos(beta);
return fuse_timer == 0 && frag->fuse_timer == 0 && dist <= nR;
}

void collisionCalc(Player *other) {
if (is_fast || other->is_fast) { // do not collide splits
return;
}
if (frag->getM() < mass) {
if (frag->fuse_timer == 0 && dist <= nR) {
return true;
}
double dist = this->calc_dist(other->x, other->y);
if (dist >= radius + other->radius) {
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@adler3d adler3d Apr 1, 2018 •
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с точки зрения производительности выгодно сравнивать квадраты расстояний, т.к вычисления корня вроде где-то в 4 раз медленнее умножения.

то есть вот так будет чуть быстрее:

double sqr_dist = this->calc_qdist(other->x, other->y);
if (sqr_dist >= sqr(radius + other->radius)) return;
...

PS: я не знаю есть ли в qt функция sqr

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пруф:
http://quick-bench.com/HY-gJwXGdunwND7FnUUAQg9rzxc

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то, что квадрат быстрее корня - мне пруфа не надо

Но если коллизия таки есть, то корень используется ниже в формуле. Для симуляции в стратегии это может и критично, в раннере это микро/наносекунды. Да и в стратегии я бы сначала посмотрел на профайлер до такой оптимизации

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В принципе если суть формулы вычисления силы коллизии оставить такой, как есть - ниже тоже можно воспользоваться квадратами и убрать ещё одно умножение, кажется

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@adler3d adler3d Apr 1, 2018 •
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Но если коллизия таки есть, то корень используется ниже в формуле

Там же O(n*n) алгоритм поиска столкновений, то есть в 99% случаев выполняется ветка где нет коллизии, поэтому она должна работать быстро.
Можно вообще только по координате X сравнить и выйти, выгоды будет больше чем от избавления от корня.

Для симуляции в стратегии это может и критично, в раннере это микро/наносекунды.

Согласен. Особенно учитывая что фрагментов редко когда больше 10.

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@DragoonXen DragoonXen Apr 1, 2018 •
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Судя по тому, что я видел, то там коллизии будут куда чаще, чем в 1% случаев.

Да, можно ускорить, я не спорю. Нужно ли

Я просто не хотел усложнять для понимания код. Кому нужно - сделают)

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@adler3d adler3d Apr 1, 2018 •
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26x
ого, реально 73% а не 99% как я думал.

return;
}

// vector from centers
double collisionVectorX = this->x - other->x;
double collisionVectorY = this->y - other->y;
// normalize to 1
double vectorLen = qSqrt(collisionVectorX * collisionVectorX + collisionVectorY * collisionVectorY);
if (vectorLen < 1e-9) { // collision object in same point??
return;
}
collisionVectorX /= vectorLen;
collisionVectorY /= vectorLen;

double collisionForce = 1. - dist / (radius + other->radius);
collisionForce *= collisionForce;
collisionForce *= COLLISION_POWER;

double sumMass = getM() + other->getM();
// calc influence on us
{
double currPart = other->getM() / sumMass; // more influence on us if other bigger and vice versa

double dx = speed * qCos(angle);
double dy = speed * qSin(angle);
dx += collisionForce * currPart * collisionVectorX;
dy += collisionForce * currPart * collisionVectorY;
this->speed = qSqrt(dx * dx + dy * dy);
this->angle = qAtan2(dy, dx);
}

// calc influence on other
{
double otherPart = getM() / sumMass;

double dx = other->speed * qCos(other->angle);
double dy = other->speed * qSin(other->angle);
dx -= collisionForce * otherPart * collisionVectorX;
dy -= collisionForce * otherPart * collisionVectorY;
other->speed = qSqrt(dx * dx + dy * dy);
other->angle = qAtan2(dy, dx);
}
return false;
}

void fusion(Player *frag) {
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19 changes: 19 additions & 0 deletions agario/local_runner/mechanic.h
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Expand Up @@ -550,6 +550,9 @@ class Mechanic : public QObject

void who_need_fusion() {
for (Player *player : player_array) {
if (player->logical == Player::FUSED) {
continue;
}
PlayerArray fragments = get_players_by_id(player->getId());
if (fragments.length() == 1) {

Expand Down Expand Up @@ -589,6 +592,22 @@ class Mechanic : public QObject
}
}
}

QSet<int> playerIds;
for (Player *player : player_array) {
playerIds.insert(player->getId());
}

for (auto sId : playerIds) {
PlayerArray fragments = get_players_by_id(sId);
for (int i = 0; i != fragments.size(); ++i) {
Player *curr = fragments[i];
for (int j = i + 1; j < fragments.size(); ++j) {
curr->collisionCalc(fragments[j]);
}
}
}

for (Player *player : player_array) {
bool changed = player->move(ins.GAME_WIDTH, ins.GAME_HEIGHT);
if (changed) {
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