So im posting this here and not under game development because this is more of a problem solving question, not directly game related.

Im making a simple RPG using xna. Im currently working on collision detection, however running into difficulty. I can successfully check for a collision between the player and a 'bad' tile, however I am stumped as to what the engine should do to prevent the player from passing throguth it!

Currently, I am getting the players based on an enum 'Direction', which is set whenever one of the 4 arrow keys are pressed. I am then creating a tmp Rectangle called checkBounds, and checking whether the players position vector, plus its velocity vector will result in a collision, is true, adding 0 to its position vector, if false, adding the velocity vector on as normal. Here are the methods:

``````public Rectangle playerBounds = new Rectangle(360, 250, PLAYER_WIDTH, PLAYER_HEIGHT); // Sets the players initial bounds

// Which way is the player facing?
public enum Direction
{
Up,
Down,
Left,
Right,
None
};

Direction dirUp = Direction.Up;
Direction dirDown = Direction.Down;
Direction dirLeft = Direction.Left;
Direction dirRight = Direction.Right;

public void Update(Player player, Core core)
{
// Gets an array list of possible key inputs.
Keys[] keys = Keyboard.GetState().GetPressedKeys();

if(keys != null && keys.Length > 0){

if (keys[0] == Keys.Up)
{
// Up arrow pressed, move player up.
CheckCollision(player, core, dirUp);
}
else if (keys[0] == Keys.Down)
{
// Down arrow pressed, move player down.
CheckCollision(player, core, dirDown);
}
else if (keys[0] == Keys.Left)
{
// Left arrow pressed, move player left.
CheckCollision(player, core, dirLeft);
}
else if (keys[0] == Keys.Right)
{
// Right arrow pressed, move player right.
CheckCollision(player, core, dirRight);
}
}

}

private void CheckCollision(Player player, Core core, Direction dir)
{

// Creates a temp storage of players new location. Used to check if the players next move will be with a bad tile.
Rectangle checkBounds = new Rectangle(player.playerBounds.X, player.playerBounds.Y, PLAYER_WIDTH, PLAYER_HEIGHT);

int width = core.collisionMap.GetLength(1);
int height = core.collisionMap.GetLength(0);

for (int y = 0; y < height; y++)
{
for (int x = 0; x < width; x++)
{
if (dir == dirUp)
checkBounds.Y += (int)player.playerVel.Z; // Player is moveing up.
if (dir == dirDown)
checkBounds.Y -= (int)player.playerVel.W; // Player is moveing down.
if (dir == dirLeft)
checkBounds.X += (int)player.playerVel.X; // Player is moveing left.
if (dir == dirRight)
checkBounds.X += (int)player.playerVel.Y; // Player is moveing right.

if (checkBounds.Intersects(core.collisionMap[y, x]))
{

// A collision was detected.
if (dir == dirUp)
player.playerBounds.Y += (int)0; // Add zero to players up direction
if (dir == dirDown)
player.playerBounds.Y -= (int)0; // Add zero to players down direction
if (dir == dirLeft)
player.playerBounds.X += (int)0; // Add zero to players left direction
if (dir == dirRight)
player.playerBounds.X += (int)0; // Add zero to players right direction

}
else
{
// A collision was not detected.

if (dir == dirUp)
player.playerBounds.Y += (int)player.playerVel.Z; // Add velocity to players up direction
if (dir == dirDown)
player.playerBounds.Y -= (int)player.playerVel.W; // Add velocity to players down direction
if (dir == dirLeft)
player.playerBounds.X += (int)player.playerVel.X; // Add velocity to players left direction
if (dir == dirRight)
player.playerBounds.X += (int)player.playerVel.Y; // Add velocity to players right direction
}
}
}
}
``````

Problem is, when I run the game, the player just dissapears off the screen?! Why is that happening, and how can I get this working?

Any and all suggestions are welcome!

Solved this myself :D

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