从（x，y）位置计算网格线C ++

Question

I have an array[15][15] with path for my object. 0 is wall, anything else makes path (1->2->3->...->end). It's a reflection of the game field of 450px x 450px(30px x 30px is one field).

For array[15][15] looking like this:

080000000000000
010111011101110
010101010101010
010101010101010
010101010101010
010101010101010
010101010101010
010101010101010
010101010101010
010101010101010
010101010101010
010101010101010
010101010101010
011101110111010
000000000000090

I get:

My object moves with some velocity * speed:

void Enemy::move()
{
    this->get_dir();
    this->x += this->velX * this->speed; // velX = -1 is left, 1 is right
    this->y += this->velY * this->speed; // velY = -1 is up, 1 is down
}

get_dir() checks what direction (velocity) it should set, like this:

void Enemy::get_dir()
{  
    Point p; // {x, y} struct

    p = this->get_grid(); // it tries to calculate X, Y axis into an array number
    if (p.y < 14 && path_grid[p.y + 1][p.x] - 1 == path_grid[p.y][p.x])
    {
        this->velY = 1;
        this->velX = 0;
        return;
    }
    /* same goes for rest of directions */

    this->velX = this->velY = 0; // if none matched it stops (reached end)
    return;
}

Point Enemy::get_grid()
{
    int x, y;

    for(y = 0;y < 15;y++)
    {
        if (this -> y >= y * 30 && this->y < (y + 1) * 30) break;
    }

    for(x = 0;x < 15;x++)
    {
        if (this -> x >= x * 30 && this->x < (x + 1) * 30) break;
    }

    return make_point(x, y);
}

But as you may notice, this will lead for my object to follow path like this:

Because it checks top left corner, and if I move right it should change the origin point, but I can't figure out how to do it. When I tried adding 30 (object bitmap size) if it goest right, it stops at the up -> right corner. What's a solution in here?

Answer 1

Have removed most of my answer, as it appears to misunderstand the question. But I will leave this part about your get_grid function being crazy. Just use maths (I assume that x and y are integers):

Point Enemy::get_grid()
{
    return make_point(x / 30, y / 30);
}

Furthermore, if you want to take your grid position and show it in the centre of a tile where each tile is 30 pixels square, then do this:

int pixelX = gridX * 30 + 15;
int pixelY = gridY * 30 + 15;

Answer 2

You should just be able to find next open position from grid but should keep track of last move just so you don't backtrack, for example:

void movePlayer(){
  const GridMap& gridMap = getGridMap(); //returns the 14x14 grid
  const Position& currentPosition = getCurrentPosition(); //returns the current player position
  const Position& previousPosition = _getPreviousPosition(); //private helper func
  //returns a list of position where the current player at the given position can move to

  //at point (x,y) you can move to NORTH,SOUTH,EAST, or WEST one unit, from the gridMap
  //using the currentPosition, return the list of cells that the player at the given position can move to.
  const PositionList& currentMovablePositions = _getMovablePosition(currentPosition,gridMap);
  //return the first matching position that isn't currentPosition or previousPosition
  const Position& nextMovePosition = _getNextMovablePosition(currentMovablePosition,currentPosition,previousPosition);

  this->animateTo( nextMovePosition );

}