碰撞检测java给出意想不到的结果

Question

My code for collision detection works but as soon as I set my players & monsters velocity to more than 1 I get weird results how can I solve this?

with velocity of 1

with velocity of 4

My collision detection:

static boolean collisionDown(Entity e)
{
    for(Block i : Game.blocks)
    {
        Rectangle player = new Rectangle(e.getX(), e.getY() + e.getVelocity(), e.getWidth(), e.getHeight());
        Rectangle block = new Rectangle(i.getX(), i.getY(), size, size );
        if (player.intersects(block))
        {
            //e.goUp(1);
            return true;
        }
    }
    return false;
}

static boolean collisionUp(Entity e)
{
    for(Block i : Game.blocks)
    {
        Rectangle player = new Rectangle(e.getX(), e.getY()  - e.getVelocity(), e.getWidth(), e.getHeight());
        Rectangle block = new Rectangle(i.getX(), i.getY(), size, size);
        if (player.intersects(block))
        {
            return true;
        }
    }
    return false;
}

static boolean collisionRight(Entity e)
{
    for(Block i : Game.blocks)
    {
        Rectangle player = new Rectangle(e.getX() + e.getVelocity(), e.getY(), e.getWidth(), e.getHeight());
        Rectangle block = new Rectangle(i.getX(), i.getY(), size, size);
        if (player.intersects(block))
        {
            return true;
        }
    }
    return false;
}

static boolean collisionLeft(Entity e)
{
    for(Block i : Game.blocks)
    {
        Rectangle player = new Rectangle(e.getX() - e.getVelocity(), e.getY(), e.getWidth(), e.getHeight());
        Rectangle block = new Rectangle(i.getX(), i.getY(), size, size);
        if (player.intersects(block))
        {
            return true;
        }
    }
    return false;
}

Where i use the collision detection

void goUp(int v)
{
    if(!Block.collisionUp(this))
        y -= v;
}

void goDown(int v)
{
    if(!Block.collisionDown(this))
        y += v;
}

void goRight(int v)
{
    if(!Block.collisionRight(this))
        x += v;
}

void goLeft(int v)
{
    if(!Block.collisionLeft(this))
        x -= v;
}

Thank you

Answer 1

Your collision methods look just fine to me, assuming you are evaluating where the character will be at the next iteration of the game. I'm willing to bet though, that when there will be a collision, you move your character at an offset to move it out of the collision box and back into a valid area to compensate. When the velocity is higher, it is magnifying this little side effect. Double check all the places that call these methods and follow the logic that follows when these methods return true (principally those in the Y direction).

An additional thing to try, increase the velocity of the character to something even higher, or something in between. If your character moves farther way and closer as you manipulate the value, this is very likely what is happening.

On a side note, note this line in all of your methods

Rectangle player = new Rectangle(e.getX(), e.getY()  - e.getVelocity(), e.getWidth(), e.getHeight());

This rectangle will not change (assuming you have not implemented threading into your game) during the duration of the method call, so recreating it every iteration of the for loop is just taking up time. Consider modifying the methods to this:

static boolean collisionDown(Entity e)
{
    Rectangle player = new Rectangle(e.getX(), e.getY() + e.getVelocity(), e.getWidth(), e.getHeight());
    for(Block i : Game.blocks)
    {
        Rectangle block = new Rectangle(i.getX(), i.getY(), size, size );
        if (player.intersects(block))
        {
            //e.goUp(1);
            return true;
        }
    }
    return false;
}

Answer 2

What I did for collision detection is develop a class called CollissionDetector . It has some logic within it for such methods as the following:

public boolean isColliding();
public boolean collided(Rectangular r1, Rectangular r2);

Rectangular is an interface with one method:

public Rectangle getRectangle();

So my CollisionDetector class worked with anything that could implement the interface called Rectangular and return a Rectangle .

The problem with some code that is supposed to detect collissions is that it reports the same collision more than once.

With my collision detector, the collission detector object would keep track of when the collision starting, whether the two objects were still colliding, and when the collision ended.

It seems like I also had a CollissionListener . I know that this is all very complex, but it did work. The CollisionListener had methods such as:

public void CollissionStarted();
public void CollissionEnded();

I wish that I could give you an SSCCE: http://sscce.org but I don't have the code anymore.