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Thread: intersects method

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    Default intersects method

    ball.jpg

    here is what i trying to do and having no luck with it.

    1st check if ball and rectangle are touching
    2nd :
    if ball intersects rect from top than i want ball to go up.
    if ball intersect rect from bottom than i want ball to go down.
    if ball intersect rect from left than i want ball to go left.
    if ball intersect rect from right than i want ball to go right.

    1st part is easy. i'll i have to do is set up a getBounds() method on ball and rect. this is the red box u see on image. than test using intersects() method if two object are touching each other.

    2nd part i have no idea how to do. the intersects() method doesnt tell you if ball is touching the rectangle from top,bottom,right,or left. this is the problem!


    if(this.getBounds_ball().intersects(this.getBounds_box())) 
    {	
    	//How to test where the ball is touching the box!!!		
    }
    plz any ideas? every one i ask seem to explain to me how to test is two object are touching each other. BUT THIS IS NOT THE PROBLEM i already know how to do this. i need help with 2nd part. not 1st part.

    any ideas? plz let me know.


  2. #2
    Super Moderator Norm's Avatar
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    Default Re: intersects method

    . the intersects() method doesnt tell you if ball is touching the rectangle from top,bottom,right,or left.
    You'll have to code that. Look at the locations of the centers of the shapes.
    If you don't understand my answer, don't ignore it, ask a question.

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    Default Re: intersects method

    ops u can igore the white line in image. i wasnt sure what i was doing there. but to find middle of shapes.

    (x+width/2)
    i am sure how to get started bc i do not even know what is the best approach.

  4. #4
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    Default Re: intersects method

    Take a piece of paper and draw the shapes in the different positions and see what the relationships are between their centers.
    If you don't understand my answer, don't ignore it, ask a question.

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    Default Re: intersects method

    i am lil confuse how will that help me to find:

    if ball intersects rect from top than i want ball to go up.
    if ball intersect rect from bottom than i want ball to go down.
    if ball intersect rect from left than i want ball to go left.
    if ball intersect rect from right than i want ball to go right.

  6. #6
    Super Moderator Norm's Avatar
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    Default Re: intersects method

    Look at the values for the x,y locations of the center of each of the shapes drawn on paper.
    For example:
    when one shape is above the other, what are their x and y values?
    when one shape is to the left of the other, what are their x and y values?
    If you don't understand my answer, don't ignore it, ask a question.

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    Default Re: intersects method

    if some one is having same problem as i do, here is a solution. i am not sure if this is the best way but it seem to be working for me. hope it helps.

    if(this.getBoundsBall().intersects(this.getBoundsRect())) 
    {	 
     
    	if(ballY+ballHeight >= rectY && ballY <= rectY)
    	{
    		System.out.println("collision from top");
    	}
    	if(ballY <= rectY+rectHeight && ballY+ballHeight >= rectY+rHeight)
    	{
    		System.out.println("collision from bottom");
    	}
    	if(ballX+ballWidth >= rectX && ballX <= rectX)
    	{
    		System.out.println("collision from left");
    	}
    	if(ballX <= rectX+rectWidth && ballX+ballWidth >= rectX+rectWidth)
    	{
    		System.out.println("collision from right");
    	}
    }

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