You can find full description here: 7C89 EagleDynamics
Used simplified ECS without Components, because currently we have only 1 type of objects: circles.
Intersection is checked by formula (without using sqrt):
float distanceSqr = Math::Vector2dUtils::getDistanceSqr(ball1.position, ball2.position);
float radiusSum = ball1.radius + ball2.radius;
return distanceSqr < radiusSum * radiusSum;For optimization, I use Quadtree with O(n log n). However, this task also could be solved by using spatial hash for example.
float a_mass = a.radius * a.radius;
float b_mass = b.radius * b.radius;
sf::Vector2f relativeVelocity = Math::Vector2dUtils::getFromToVec(a.velocity, b.velocity);
sf::Vector2f relativePosition = Math::Vector2dUtils::getDistanceUnitVec(a.position, b.position);
float velocityAlongNormal = Math::Vector2dUtils::dotProduct(relativeVelocity, relativePosition);
if (velocityAlongNormal > 0) {
return;
}
float e = 1.0; // Coefficient of restitution
float j = -(1 + e) * velocityAlongNormal;
j /= 1 / a_mass + 1 / b_mass;
// Apply impulse
sf::Vector2f impulse = relativePosition * j;
a.velocity -= impulse / a_mass;
b.velocity += impulse / b_mass;Due to poor optimization I turned off quadtree draw by default. You can enable debug draw of quadtree by uncommenting 1 line at src/engine/Game.cpp
void Game::initSystems() {
systems_.push_back(std::make_unique<DrawSystem>(window_.get(), world_.get()));
systems_.push_back(std::make_unique<FpsDebugSystem>(window_.get(), world_.get()));
systems_.push_back(std::make_unique<MovementSystem>(world_.get()));
systems_.push_back(std::make_unique<CollisionSystem>(window_.get(), world_.get()));
// Warning: DrawCollisionSystem is highly unoptimized. Should be used only for debug purposes.
// Uncomment line below to see quadtree
//systems_.push_back(std::make_unique<DrawCollisionSystem>(window_.get(), world_.get()));
}In case of using Visual Studio, you can build the project for Visual Studio by using command:
cmake -G "Visual Studio 10"