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#include <cmath>

    10

    : tick_timer(PHYSICS_TICK_MS), gravity(gravity), dimensions(dimensions), terrain(dimensions.x, std::vector<TerrainType>(dimensions.y, EMPTY)) {

    11

    12

	generateTerrain(1337);

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    for (std::vector<PhysicsObject*>::iterator i = objects.begin(); i != objects.end(); i++) {

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        (*i)->tick(); 

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    }

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/**

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 * Updates object speed and position. This function organises force

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 * integration and collision detection.

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 */   

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void PhysicsObject::updatePosition () {

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    // Add gravity to the force queue

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    forceq.push(world.gravity);

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    // Go trough every force in the queue

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    // TODO: It might be possible to optimize by adding forces together

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    Force total;

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    posAfterTick = position;

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    velAfterTick = velocity;

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    while (!forceq.empty()) {

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        total += forceq.front();

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        forceq.pop();

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        //        Engine::log(DEBUG, "PhysicsObject.updatePosition") << "Current position: " << posAfterTick;

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    }

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    integrate(total, PHYSICS_TICK_MS);

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    Vector newPosition = posAfterTick /*+ (velAfterTick * PHYSICS_TICK_MS)/1000*/;

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    this->velocity = velAfterTick;

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    //Engine::log(DEBUG, "PhysicsObject.updatePosition") << "Nopeus: "<<this->velocity;

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    /*

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    this->velocity += world.gravity * (PHYSICS_TICK_MS / 1000.0);

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    */

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    //goes 1 unit forward every step and check if has hit anything

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    Vector unitVector = (newPosition-position) / (newPosition-position).length();

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	Vector tmpVector = position;

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    Vector reached = position;

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	int steps = (int) (newPosition-position).length();

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    for(int i = 0; i < steps; i++) {

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        tmpVector += unitVector;

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        if(world.getType(tmpVector) != EMPTY) {

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			//Engine::log(DEBUG, "physics.update_position") << "hit something";

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            // Then we have hit something

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            reached = position + unitVector*(i-1);

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            collided = true;

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            break;

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        } else {

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			//Engine::log(DEBUG, "physics.update_position") << "didnt hit";

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    }

    88

    // In case of some float error

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        if(world.getType(newPosition)) {

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            // There was error, and there is ground

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            newPosition = tmpVector;

    93

        } else {

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            // This means everything was ok, so no need to do anything

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        }

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    } else {

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        newPosition = reached;

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        this->velocity = Vector(0, 0);

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        //TODO: it shouldn't just stop on collision

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    this->position = newPosition;

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   105

bool PhysicsWorld::collided (Vector oldPos, Vector newPos) {

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    int deltaX = oldPos.x - newPos.x; 

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    int deltaY = oldPos.y - newPos.y; 

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    double distance = sqrt(deltaX * deltaX + deltaY * deltaY);

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    double xInc = deltaX / distance;

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    double yInc = deltaY / distance;

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    double currentX = oldPos.x;

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    double currentY = oldPos.y;

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    // This implementation is bit slow since it checks some squares twice.

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    for(unsigned int i = 1; i < distance; i++) {

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        currentX += xInc;

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        currentY += yInc;

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        if(terrain[(int)currentX][(int)currentY] != EMPTY)

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            return true;

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    }

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    return false;

   122

}

   123

   124

/**

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 * Integrates given force over time and stores new position to

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 * posAfterTick and new velocity to velAfterTick.

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 * @param force Force vector.

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 * @param dt The time the force is applied (<=PHYSICS_TICK_MS)

   129

 */

   130

void PhysicsObject::integrate(Force force, TimeMS dt) {

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    Derivative tmpd;

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    Derivative k1 = evaluate(force, 0, tmpd);

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    Derivative k2 = evaluate(force, 0.5f*dt, k1);

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    Derivative k3 = evaluate(force, 0.5f*dt, k2);

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    Derivative k4 = evaluate(force, dt, k3);

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    const Vector dxdt = (k1.dx + (k2.dx + k3.dx) * 2.0f + k4.dx) * 1.0f/6.0f;

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    const Vector dvdt = (k1.dv + (k2.dv + k3.dv) * 2.0f + k4.dv) * 1.0f/6.0f;

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    //    Engine::log(DEBUG, "PhysicsObject.integrate") << "Changes: "<< dxdt << " " << dvdt << " Time: " <<dt;

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    posAfterTick = posAfterTick + (dxdt * dt)/1000;

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    velAfterTick = velAfterTick + (dvdt * dt)/1000;

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    //Engine::log(DEBUG, "PhysicsObject.integrate") << "velAfterTick: " << velAfterTick;

   145

}

   146

   147

Derivative PhysicsObject::evaluate(Force force, TimeMS dt, Derivative &d) {

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    Vector curPos = posAfterTick + (d.dx*dt)/1000;

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    Vector curVel = velAfterTick + (d.dv*dt)/1000;

   150

   151

    Derivative out;

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    out.dx = curVel;

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    out.dv = acceleration(force);

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    //Engine::log(DEBUG, "PhysicsObject.evaluate") << "Out.dx: " << out.dx;

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    return out;

   156

}

   157

   158

Vector PhysicsObject::acceleration(const Force &force) {

   159

    return (force/mass);

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}

   161

   162

/**

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 * Adds force to the force queue. Force queue is emptied on each

   164

 * tick. Forces that last over one tick are also handled.

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 * @param force Force vector.

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 * @param dt The time the force is applied.

   167

 */

   168

void PhysicsObject::applyForce (Force force, TimeMS dt) {

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    // Add applied force to the queue

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    forceq.push(force);

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/**

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 * simple random map generation

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 * first fills whole level with dirt

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 * then randomizes circles of empty or rock

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 * @param seed - seed number for random number generator

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 */

   192

void PhysicsWorld::generateTerrain(int seed) {

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    // generating should use own random number generator, but didn't find easily how that is done

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    srand(seed);

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    // some constants to control random generation

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    const int min_range = 10;

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    const int max_range = 40;

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    const int num = 1;

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    const int rock_rarity = 4; // 1 / rock_rarity will be rock circle

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    // loops for amount of circles

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    for(int i = 0; i < num; i++) {

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        // information of new circle

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        int midx = rand()%(int)dimensions.x;

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        int midy = rand()%(int)dimensions.y;

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        int range = rand()%(max_range-min_range)+min_range;

   208

   209

        // put first circle in the middle of the cave

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		// so that we have some area we can certainly spawn into 

   211

		if(i == 0) {

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			midx = 60;

   213

			midy = 60;

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			range = 50;

   215

		}

   216

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        TerrainType type = DIRT;

   218

        if(rand()%rock_rarity == 0) {

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            type = ROCK;

   220

        }

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        // loops for every pixel of circle

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        for(int x = std::max(0, midx-range); x < std::min((int)dimensions.x, midx+range); x++) {

   223

            for(int y = std::max(0, midy-range); y < std::min((int)dimensions.y, midy+range); y++) {

   224

                if(x*x+y*y < range*range) {

   225

                    // and sets it to type

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                    terrain[x][y] = type;

   227

                }

   228

            }

   229

        }

   230

    }

   231

}

   232

   233

/**

   234

 * Returns terrainType in given tile. ROCK if tile is out of area

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 * @param pos - coordinate of tile

   236

 */

   237

TerrainType PhysicsWorld::getType(Vector pos) const {

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    int x = (int)(pos.x);

   239

    int y = (int)(pos.y);

   240

    if(x < 0 || y < 0 || x >= dimensions.x || y >= dimensions.y) {

   241

        return ROCK;

   242

    }

   243

    return terrain[x][y];

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}