I have an array for the x co-ordinate of the bricks, an array for the y co-ordinates of the bricks and an array to show weather it is visible. My code reads like this:
if (Visible[0] == 1)
{
paper.DrawRectangle(pen, BrickX[0], BrickY[0], 50, 10);
}
and for my collision for the ball to hit the brick, the code reads:
if (Visible[0] == 1)
{
if ((x >= BrickX[0]) && (x <= BrickX[0] + 50))
{
if ((y >= picDisplayBat.Height - 190) && (y <= BrickY[0] + 10))
yChange = -yChange;
Visible[0] = 0;
This does not seem to work as when the ball comes close the brick, the brick dissapears before the collision has happened and the ball goes straight through it. any suggestions?
You're missing brackets around your second if test.
Regardless of the outcome of the test the brick gets set to invisible. Your code is effectively this:
if ((y >= picDisplayBat.Height - 190) && (y <= BrickY[0] + 10))
{
yChange = -yChange;
}
Visible[0] = 0;
You want this:
if ((y >= picDisplayBat.Height - 190) && (y <= BrickY[0] + 10))
{
yChange = -yChange;
Visible[0] = 0;
}
I won't answer your question exactly, but this might help.
It's kind of unobvious what your code does now. Why always [0]?
Just create a class called Brick and a class called Ball:
class Brick {
public double x, y;
public double size;
public bool visible;
};
class Ball {
public double x, y;
public double size;
};
Now introduce the member in the Brick called bool Intersects(Ball ball), which yields true if the ball intersects with the brick (you could simply check this by their bounding boxes).
Now your checks become extremely simple (I assume you have an array of bricks somewhere called bricks).
foreach (Brick brick in bricks) {
if (brick.visible && brick.Intersects(ball)) {
// Hide the brick
brick.visible = false;
}
}
In short, I think you are doing your steps out of order.
Your second routine is perhaps doing too much. It should only determine a collision, and return an identifier for the target of the collision. Then a consuming routine uses that information to adjust projectile trajectory (reflect it back) and finally turn-off the visibility.
By the way, collision detection is a popular venue for what is known as "double-dispatch" invocations. Consider using the visitor pattern (ala Gang of Four) as a way to code this up.
Related
I am currently creating a brickbreaker clone (yeah, another) and have the ball-brick collision for 1 brick. I have 4 other bricks commented out, because when the ball collides with the brick I have the right code for, it just removes all bricks rather than the specific one it collided with. Also, the ball only collides with the first brick when the ball is near the top left corner of the game screen (pretty far from the actual brick). I'm really not sure what to do, I have tried spacing the bricks out a bit more but that didn't help.
int score = 0;
if ((ballY > picBrk1.Height) && (ballY < picBrk1.Height + 30) && (ballX > picBrk1.Width) && (ballX < picBrk1.Width + 71))
{
// ball rebounds off brick
yChange = -yChange;
// each brick adds 1 to score
score = score + 1;
lblScore.Text = "Score: " + score;
picBrk1.Visible = false;
}
You need to be very clear about the localisation of your bricks.
I suggest adding a UpperLeft property to your Brick class:
public class Brick
{
/* your other properties here */
public Point UpperLeft {get; set;}
}
Make sure UpperLeft value is properly set to the coordinates of the upper left corner of your brick.
My assumption is that your X and Y follow the standard computer image representation where 0,0 is the top left corner of the image and y increases when you go south (which is different from the usual mathematical standard).
Then your collision check will be:
Point ballRelativeToBrick1 = new Point(
ballX - picBrick1.UpperLeft.X,
ballY - picBrick1.UpperLeft.Y)
bool collide = 0 < ballRelativeToBrick1.X && ballRelativeToBrick1.X < picBrick1.Width
&& 0 < ballRelativeToBrick.Y && ballRelativeToBrick.Y < picBrick1.Height
I'm working on a small game, I have objects which I want to elevate up and down. Object moves to max value of Y -> Object moves to min value of Y -> Repeat. I have a rough idea of how to do this, I would put this in a timer/my update method.
if(Y >= max)
{
direction = "down";
}
if(y =< min)
{
direction = "up";
}
if(direction == "up") Y -= speed;
if(direction == "down") Y += speed;
(Could also use a bool ofcourse but, for the sake of implicity)
But it feels like I'm just re-inventing the wheel, is there by any chance a built in method/math function to do this automatically? eg. SomeFunction(min, max, increment).
I'm using the XNA framework, so functions built into that are ofcourse welcome as well.
Forget having a separate direction flag.
Just use a negative speed for "up" to simplify the code:
if ((Y >= max) || (Y <= min)) // Hit an edge?
speed = -speed; // Reverse direction.
Y += speed;
I have a bouncing ball application and I have to extend it to prevent overlapping of the balls.
When ball overlaps another, they should move away as in real life.
I have to extend the given MoveBall method:
private void MoveBall()
{
prevX = x;
prevY = y;
x += xVelocity;
y += yVelocity;
// Is there too closed ball?
foreach (Ball ball in parentForm.balls)
{
distance = Math.Sqrt(Math.Pow((double)(ball.prevX - prevX), 2) +
Math.Pow((double)(ball.prevY- prevY), 2));
overlap = ((radius + ball.radius) - distance);// +ball.radius;
if (ball.id != this.id &&
ball.id != lastID &&
overlap > 0)
{
lastID = this.id;
if (xVelocity > 0) // roading right
{
xVelocity = -xVelocity;
x -= xVelocity - ball.xVelocity;
}
else if (xVelocity <= 0) // roading left
{
xVelocity = -xVelocity;
x += xVelocity + ball.xVelocity;
}
if (yVelocity > 0)
{ // going up
yVelocity = -yVelocity;
y -= yVelocity - ball.yVelocity;
}
else if (yVelocity <= 0) // down
{
yVelocity = -yVelocity;
y += yVelocity + ball.yVelocity;
}
}
}
// ***********************************************
// ***************** END MY CODE *****************
if (x > parentForm.Width - 10 - (radius) || x < 0)
{
if (x < 0) x = 0;
if (x > parentForm.Width - 10) x = parentForm.Width - 10 - radius;
xVelocity = -xVelocity;
}
if (y > parentForm.Height - 40 - (radius) || y < 0)
{
if (y < 0) y = 0;
if (y > parentForm.Height - 40) y = parentForm.Height - 40 - (radius);
yVelocity = -yVelocity;
}
}
x,y, xVelocity, yVelocity, radius, prevX, prevY declared as int.
overlap, distance as double.
When 2 overlap, they are getting stuck. Why?
Unfortunately, I can't upload all source code because there are lot of modules.
I'm using Visual C# Express 2010.
As no Question is asked explicitly, I will assume the question "Why are the balls sticking together?"
You have only shown one loop in source code, that's not enough ;-) To check all possible collisions, you need to check n*(n-1)/2 possible collisions. That is normally done with two loops. You have to put in careful measures to avoid handling the same collision twice.
The reason that your balls get stuck is that you handle the same collision multiple times. For example two balls colliding exactly horizontal: The left one has velocity 5 and x-position of 100. The other one shall have a position of 110 and velocity of -6. When the collision happens:
x is set to 105.
Collision detected: x is set to 104 and velocity to -5.
The other Ball handles the same collision:
He moves according to his velocity to position 104.
Collision handling: His velocity becomes 6 and position becomes 105.
The balls were at 100 and 110 resp. and have been moved to 104 and 105. While the velocities are now pointing away from each other, the collision handling in the following step will invert them again. So the positions are close together and the velocities are changing sign every frame. The balls seem "stuck to each other".
I hope the answer helps you to understand your problem. For a better implementation of an elastic collision (that handles each collision exactly once) look here: Ball to Ball Collision - Detection and Handling
Having stumbled upon similar issues when I made my first attempts at collision detection algorithms, I'll try to describe what I think is the problem here.
Maybe the balls move fast enough so that, before collision is even detected by your code, they are already partially "inside" each other. When collision detection comes and notices that, it does what it's supposed to do: change the planned trajectories of the objects according to the details of the collision that just happened. The problem is that, because these objects got sort-of "merged" before collision detection caught them, they can't get unstuck because collision detection is fired again, trapping them with each other.
If this is the source of the problem, then maybe the above code would work with a small enough velocity vector. Of course, that's not a real solution, but if it does work for very small velocities, it probably confirms my hypothesis and you have some idea regarding how to proceed.
I'm working on an assignment for uni where I have to create a Breakout game in Visual Studio 2010 using C# Win Forms. At the moment, I am concentrating on there being only one brick to be destroyed so I have the mechanics down before expanding on it.
To clarify about my current program: I am using a picture box as a Graphics object and a timer to create the animation effect. The ball can skip, at each frame, between 1 and 10 pixels — this is part of creating a random starting vector for the ball.
This works fine until it comes to checking if the ball has 'hit' the brick I have drawn. What I have is an if statement that checks if the ball is at any of the coordinates on the picture box that corresponds to the outline of the brick. I know that the logic is fine because it works some of the time. However, because of the variation in the 'jumping' of the ball's position, I need to add a buffer area of +/- 5 pixels to my if statement.
This is where the problem arises, because my if statement (two, really) is really complicated as it is:
// Checks if ball hits left side or top of brick
if (((x >= brickX) && (x <= (brickX + 50)) && (y == brickY)) ||
((y >= brickY) && (y <= (brickY + 20)) && (x == brickX)))
{
brickHit = true;
}
// Check if ball hits right side or bottom of brick
else if ((((x >= brickX) && (x <= brickX + 50)) && (y == (brickY + 20))) ||
(((y >= brickY) && (y <= brickY + 20)) && (x == brickX + 50)))
{
brickHit = true;
}
For clarification: x and y are the coordinates of the ball and brickX and brickY are the coordinates of the top-left corner of the rectangle brick (which is 50 pixels wide, 10 pixels high).
Is there any way to simplify the above if statements? If I can make them simpler, I know it'll be much easier to add in the 'buffer' (which only needs to be 5 pixels either side of the brick's outline' to allow for the ball's change in position).
If further clarification is needed, please ask — I'm writing this question at 5:12am so I know I might be a little unclear.
One way you could possible simplify this (and I may be misunderstanding your spec), but you can make a Rectangle out of the bounds of the brick and check the Contains for your x,y point.
Rectangle rec = new Rectangle(brickX, brickY, 50, 20);
rec.Offset(-5, -5);
rec.Inflate(10, 10);
if (rec.Contains(new Point(x,y))
{
brickHit = true;
}
brickHit = new Rectangle(brickX,brickY,50,20).Contains(x,y);
Adding a buffer:
int buffer = 5;
brickHit = new Rectangle(brickX,brickY,50,20).Inflate(buffer,buffer).Contains(x,y);
The Rectagle class can come in handy sometimes.
This worked for me:
var rect1 = new System.Drawing.Rectangle(pictureBox1.Location,
pictureBox1.Size);
var rect2 = new System.Drawing.Rectangle(pictureBox2.Location,
pictureBox2.Size);
if (rect1.IntersectsWith(rect2))
{
//code when collided
}
I am stuck trying to figure out how to alter my collision detection to work correctly, i got all my wall objects stacked inside a List and then when the player moves i loop thru each wall object and call the DetectCollision method, this returns true or false depending on if the object is inside the wall or not.
Wall detect collision (X- and Y-coordinate is the position of the wall)
public bool DetectCollision(float x, float y)
{
if ((x >= this.XCoordinate && x <= (this.XCoordinate + this.BlockWidth)) && (y >= this.YCoordinate && y <= (this.YCoordinate + this.BlockHeight)))
return true;
else
return false;
}
So in my player function when the player tries to move, i add the movement to a temporary X,Y coordinate and check if those Collide against the wall, if they do nothing happens, otherwise i move the player.
But i have noticed that it doesn't work as it should be, if i add a piece of wall inside of the gamefield it only checks the bottom right corner for collision detection?
Player movement method:
float x, y;
if (direction == Direction.E)
{
x = LiveObjects.player.XCoordinate - MovementSpeed;
y = LiveObjects.player.YCoordinate;
}
else if (direction == Direction.W)
{
x = LiveObjects.player.XCoordinate + MovementSpeed;
y = LiveObjects.player.YCoordinate;
}
else if (direction == Direction.N)
{
x = LiveObjects.player.XCoordinate;
y = LiveObjects.player.YCoordinate - MovementSpeed;
}
else
{
x = LiveObjects.player.XCoordinate;
y = LiveObjects.player.YCoordinate + MovementSpeed;
}
if (GameMechanics.DetectWallCollision(x, y) || GameMechanics.DetectWallCollision((x + LiveObjects.player.BlockWidth), (y + LiveObjects.player.BlockHeight))
{
OnPlayerInvalidMove(null, new PlayerEventArgs());
return;
}
and the loop for DetectWallCollision is just:
foreach (Wall wall in LiveObjects.walls)
{
if (wall.DetectCollision(x, y))
return true;
}
return false;
Any ideas?
I'm assuming there isn't anything in your world that is infinitely small (i.e. is the size of a pixel). To have true bounding box collision, you've got to consider the size of both objects, not just one.
boolean intersectsEntity(Entity e)
{
return (e.position.x <= position.x + size.x) &&
(e.position.y <= position.y + size.y) &&
(e.position.x + e.size.x >= position.x) &&
(e.position.y + e.size.y >= position.y);
}
That's of course assuming an Entity has a vector for its position and for its size. So size.x == width, and size.y == height.
There is something that disturbs me, you said that the DetectCollision method gets the position of the wall - but if I interpret your code correctly you hand to the DetectWallCollision the x and y parameter which is the position (after movement) of the player and hand that position down to the DetectCollision method...
have you debugged your code to see what coordinates are passed to the collision methods and traced the routes your if-statements are going?
if it is not possible to debug your code for whatever reason - write a trace file - I think the solution will fall into your lap ;)
Your east and west are the wrong way around. With a coordinate system of 0,0 at the top left, increasing positively as you move down or to the right, then a movement West would normally mean a movement left, which means decreasing values of X, and the reverse for East. You are doing the opposite.