Sprite Collision - GameCreators Forum

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Marsh0

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Posted: 28th Jan 2010 18:14

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Hello i am making a simple Pong game. The problem i have run into is that i cannot get dbSpriteCollision to work. Once in awhile it will work but the majority of the time the ball will go right through the paddle.

here is my code. The return is there so that it will exit when it hits so i know something actually happened.

+ Code Snippet

		// If the ball Collides with a paddle
		if (dbSpriteHit(3,2) == 1 || dbSpriteHit(2,3) == 1)
		{
                   return;
		}

It works fine for the computer though i have it lining both x coordinates up exactly which is probably why it works. Any ideas on how i would detect the second the ball hits anywhere on the paddle?

Thanks for any help

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Mireben

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Posted: 30th Jan 2010 11:34

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In the first sentence you mention dbSpriteCollision, then show a code which contains dbSpriteHit. These are, AFAIK, not interchangeable. dbSpriteHit detects when the sprites are lined up alongside each other, while dbSpriteCollision detects overlap. For a fast moving ball, only overlap detection is suitable because it will almost never be lined up with the paddle.

If you use dbSpriteCollision and still cannot get it working, post some more code because from this is not really possible to spot the problem.

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Marsh0

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Posted: 30th Jan 2010 17:44 Edited at: 30th Jan 2010 17:58

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I used both and could not get either to work. I am not sure what other code i should post. Its in a loop it should work fine. Here is my entire code. its not to long at the moment.

#include "DarkGDK.h"
#include <stdio.h>

void DarkGDK ( void )
{

dbSyncOn   ( );
	dbSyncRate ( 60 );

dbDisableEscapeKey ( );
	dbRandomize ( dbTimer ( ) );

// Setup the backdrop for are game
	dbLoadImage ( "backdrop.bmp", 1 );
	dbSprite ( 1, 0, 0, 1 );

// Make yellow transparent on sprites
	dbSetImageColorKey ( 255, 255, 0 );

// Create the game sprites, such as the paddle and the ball.
	dbCreateAnimatedSprite(2,"paddle.bmp",1,4,2);
	dbCreateAnimatedSprite(3,"ball.bmp",1,1,3);

// Declare are Shiz
	int Score, AiScore, playerx, playery, compx, compy, ballx, bally;
	byte ballmove, PlayerSpeed, CompSpeed, BallSpeed;
	PlayerSpeed = 5; CompSpeed = 5; BallSpeed = 2;
	ballmove = 0; Score = 0; AiScore = 0; playerx = 280; playery = 450; compx = 280; compy = 15; ballx = 300; bally = 230;

// Set initial bar movement direction
	ballmove = dbRnd(3);

while ( LoopGDK ( ) )
	{

dbOffsetSprite ( 2,playerx + 50, playery ) ;

// Draw Sprites first so text will show up
		dbDrawSpritesFirst();

// Put a period on paddle position and ball position useful for debugging
		dbText ( playerx, playery, ".");
		dbText ( compx, compy, ".");
		dbText ( ballx, bally, ".");

// Set up Text
		dbSetTextFont("Trajan Pro");
		dbSetTextToBold();
		dbSetTextSize (22);

// Draw Score
		dbInk(dbRgb(255,0,0),0); 
		dbText (5,5,"Player1:");
		dbText (90,6,dbStr(Score));
		
		dbInk(dbRgb(0,255,0),0); 
		dbText (5,20,"Computer:");
		dbText (115,20,dbStr(AiScore));

// Make Text Red
		dbInk(dbRgb(255,0,0),0); 
		// show fps
		dbText( 555 , 5, "FPS: " );
		dbText ( 600, 5, dbStr(dbScreenFPS()));

// Show Curser Position
		dbText( 555 , 20, "M X: " );
		dbText( 555 , 35, "M Y: " );

dbText ( 600, 20, dbStr(dbMouseX()));
		dbText ( 600, 35, dbStr(dbMouseY()));

// Show the Players Paddle Position
		dbText( 555 , 50, "PP: " );
		dbText ( 600, 50, dbStr(playerx));

// Show the ball Position
		dbText( 555 , 65, "Ball: " );
		dbText ( 600, 65, dbStr(ballx));

// When user presses Left on the Keyboard and make sure the paddle position doesnt go off the screen.
		if (dbLeftKey() == 1 && playerx > 0)
		{
			dbSprite ( 2, playerx = playerx - PlayerSpeed, playery, 2 );	
		}

// When user presses Right on the Keyboard and make sure the paddle position doesnt go off the screen.
		if (dbRightKey() == 1 && playerx < 550)
		{
			dbSprite ( 2, playerx = playerx + PlayerSpeed, playery, 2 );
		}

// Computer Movement Crappy Ai code
		if (ballx > compx)
		{
		dbSprite ( 2, compx = compx + CompSpeed, compy, 2 );
		}

if (ballx < compx)
		{
		dbSprite ( 2, compx = compx - CompSpeed, compy, 2 );
		}

// If the ball Collides with a paddle
		if (dbSpriteCollision(3,2) == 1 || dbSpriteCollision(2,3) == 1)
		{

// Detect which paddle it hit
			if (bally > 400) // Hit Players Paddle so only move the ball up
			{
				// Move ball in a random direction but only up.
				ballmove = dbRnd(1);
			}

// Detect which paddle it hit
			if (bally < 70) // Hit Computers Paddle so only move the ball up
			{
				// Move ball in a random direction but only Down.
				ballmove = dbRnd(3);

// If its going to randomize a number to make it move up then reset it.
				if (ballmove == 0) {ballmove = 2;}
				if (ballmove == 0) {ballmove = 3;}
			}

}

// If the ball Collides with a wall || means or
		if (ballx < 0 || ballx > 600)
		{
			// Check what direction the ball is moving in. So the direction isnt back the way it came
			if (ballmove == 1 || ballmove == 0) // Ball is moving up
			{
				// Hit the left wall. So only bounce Right and Up
				if (ballx < 0)
				{
					ballmove = 0;
				}

// Hit the Right wall. So only bounce Left and Up
				if (ballx > 640)
				{
					ballmove = 1;
				}
			}

// Check what direction the ball is moving in. So the direction isnt back the way it came
			if (ballmove == 2 || ballmove == 3) // Ball is moving down
			{
				// Hit the left wall. So only bounce Right and Down
				if (ballx < 0)
				{
					ballmove = 2;
				}

// Hit the Right wall. So only bounce Left and Down
				if (ballx > 640)
				{
					ballmove = 3;
				}
			}
		}

// If the ball goes into the computers goal
		if (bally < 0)
		{
			// Set ball back to start position
			ballx = 300; bally = 230;

// Move ball in a random direction
			ballmove = dbRnd(3);

// Adjust Score ++ adds one to score Score++; also works
			++Score;
		}

// If the ball goes into the Players goal
		if (bally > 480)
		{
			// Set ball back to start position
			ballx = 300; bally = 230;

// Move ball in a random direction
			ballmove = dbRnd(3);

// Adjust Score ++ adds one to score AiScore++; also works
			++AiScore;
		}

// Select Sprite from Sheet and set to position we just declared above.

// Set Sprite to your paddle
	dbSetSpriteFrame(2,1);
	dbPasteSprite ( 2, playerx, playery );

// Set Sprite to enemies paddle
	dbSetSpriteFrame(2,3);
	dbPasteSprite ( 2, compx, compy );

if (ballmove == 0)
	{
		dbSprite ( 3, ballx = ballx + BallSpeed, bally = bally - BallSpeed, 3 );
	}

if (ballmove == 1)
	{
		dbSprite ( 3, ballx = ballx - BallSpeed, bally = bally - BallSpeed, 3 );
	}

if (ballmove == 2)
	{
		dbSprite ( 3, ballx = ballx + BallSpeed, bally = bally + BallSpeed, 3 );
	}
	
	if (ballmove == 3)
	{
		dbSprite ( 3, ballx = ballx - BallSpeed, bally = bally + BallSpeed, 3 );
	}

if ( dbEscapeKey ( ) ) {  break; }
	dbSync ( );

}

return;
}

+ Code Snippet


#include "DarkGDK.h"
#include <stdio.h>


void DarkGDK ( void )
{

	dbSyncOn   ( );
	dbSyncRate ( 60 );

	dbDisableEscapeKey ( );
	dbRandomize ( dbTimer ( ) );

	// Setup the backdrop for are game
	dbLoadImage ( "backdrop.bmp", 1 );
	dbSprite ( 1, 0, 0, 1 );

	// Make yellow transparent on sprites
	dbSetImageColorKey ( 255, 255, 0 );

	// Create the game sprites, such as the paddle and the ball.
	dbCreateAnimatedSprite(2,"paddle.bmp",1,4,2);
	dbCreateAnimatedSprite(3,"ball.bmp",1,1,3);

	// Declare are Shiz
	int Score, AiScore, playerx, playery, compx, compy, ballx, bally;
	byte ballmove, PlayerSpeed, CompSpeed, BallSpeed;
	PlayerSpeed = 5; CompSpeed = 5; BallSpeed = 2;
	ballmove = 0; Score = 0; AiScore = 0; playerx = 280; playery = 450; compx = 280; compy = 15; ballx = 300; bally = 230;

	
// Set initial bar movement direction
	ballmove = dbRnd(3);

	while ( LoopGDK ( ) )
	{

		dbOffsetSprite ( 2,playerx + 50, playery ) ;

		// Draw Sprites first so text will show up
		dbDrawSpritesFirst(); 

		// Put a period on paddle position and ball position useful for debugging
		dbText ( playerx, playery, ".");
		dbText ( compx, compy, ".");
		dbText ( ballx, bally, ".");

		// Set up Text
		dbSetTextFont("Trajan Pro");
		dbSetTextToBold();
		dbSetTextSize (22);

		// Draw Score
		dbInk(dbRgb(255,0,0),0); 
		dbText (5,5,"Player1:");
		dbText (90,6,dbStr(Score));
		
		dbInk(dbRgb(0,255,0),0); 
		dbText (5,20,"Computer:");
		dbText (115,20,dbStr(AiScore));

		// Make Text Red
		dbInk(dbRgb(255,0,0),0); 
		// show fps
		dbText( 555 , 5, "FPS: " );
		dbText ( 600, 5, dbStr(dbScreenFPS()));

		// Show Curser Position
		dbText( 555 , 20, "M X: " );
		dbText( 555 , 35, "M Y: " );

		dbText ( 600, 20, dbStr(dbMouseX()));
		dbText ( 600, 35, dbStr(dbMouseY()));

		// Show the Players Paddle Position
		dbText( 555 , 50, "PP: " );
		dbText ( 600, 50, dbStr(playerx));

		// Show the ball Position
		dbText( 555 , 65, "Ball: " );
		dbText ( 600, 65, dbStr(ballx));


		// When user presses Left on the Keyboard and make sure the paddle position doesnt go off the screen.
		if (dbLeftKey() == 1 && playerx > 0)
		{
			dbSprite ( 2, playerx = playerx - PlayerSpeed, playery, 2 );	
		}

		// When user presses Right on the Keyboard and make sure the paddle position doesnt go off the screen.
		if (dbRightKey() == 1 && playerx < 550)
		{
			dbSprite ( 2, playerx = playerx + PlayerSpeed, playery, 2 );
		}


		// Computer Movement Crappy Ai code
		if (ballx > compx)
		{
		dbSprite ( 2, compx = compx + CompSpeed, compy, 2 );
		}

		if (ballx < compx)
		{
		dbSprite ( 2, compx = compx - CompSpeed, compy, 2 );
		}



		// If the ball Collides with a paddle
		if (dbSpriteCollision(3,2) == 1 || dbSpriteCollision(2,3) == 1)
		{

			// Detect which paddle it hit
			if (bally > 400) // Hit Players Paddle so only move the ball up
			{
				// Move ball in a random direction but only up.
				ballmove = dbRnd(1);
			}

			// Detect which paddle it hit
			if (bally < 70) // Hit Computers Paddle so only move the ball up
			{
				// Move ball in a random direction but only Down.
				ballmove = dbRnd(3);

				// If its going to randomize a number to make it move up then reset it.
				if (ballmove == 0) {ballmove = 2;}
				if (ballmove == 0) {ballmove = 3;}
			}

		}

		// If the ball Collides with a wall || means or
		if (ballx < 0 || ballx > 600)
		{
			// Check what direction the ball is moving in. So the direction isnt back the way it came
			if (ballmove == 1 || ballmove == 0) // Ball is moving up
			{
				// Hit the left wall. So only bounce Right and Up
				if (ballx < 0)
				{
					ballmove = 0;
				}

				// Hit the Right wall. So only bounce Left and Up
				if (ballx > 640)
				{
					ballmove = 1;
				}
			}

			// Check what direction the ball is moving in. So the direction isnt back the way it came
			if (ballmove == 2 || ballmove == 3) // Ball is moving down
			{
				// Hit the left wall. So only bounce Right and Down
				if (ballx < 0)
				{
					ballmove = 2;
				}

				// Hit the Right wall. So only bounce Left and Down
				if (ballx > 640)
				{
					ballmove = 3;
				}
			}
		}

		// If the ball goes into the computers goal
		if (bally < 0)
		{
			// Set ball back to start position
			ballx = 300; bally = 230;

			// Move ball in a random direction
			ballmove = dbRnd(3);

			// Adjust Score ++ adds one to score Score++; also works
			++Score;
		}

		// If the ball goes into the Players goal
		if (bally > 480)
		{
			// Set ball back to start position
			ballx = 300; bally = 230;

			// Move ball in a random direction
			ballmove = dbRnd(3);

			// Adjust Score ++ adds one to score AiScore++; also works
			++AiScore;
		}

	// Select Sprite from Sheet and set to position we just declared above.

	// Set Sprite to your paddle
	dbSetSpriteFrame(2,1);
	dbPasteSprite ( 2, playerx, playery );

	// Set Sprite to enemies paddle
	dbSetSpriteFrame(2,3);
	dbPasteSprite ( 2, compx, compy );


	
	if (ballmove == 0)
	{
		dbSprite ( 3, ballx = ballx + BallSpeed, bally = bally - BallSpeed, 3 );
	}	

	if (ballmove == 1)
	{
		dbSprite ( 3, ballx = ballx - BallSpeed, bally = bally - BallSpeed, 3 );
	}	

	if (ballmove == 2)
	{
		dbSprite ( 3, ballx = ballx + BallSpeed, bally = bally + BallSpeed, 3 );
	}
	
	if (ballmove == 3)
	{
		dbSprite ( 3, ballx = ballx - BallSpeed, bally = bally + BallSpeed, 3 );
	}	





	if ( dbEscapeKey ( ) ) {  break; }
	dbSync ( );


	}

	return;
}

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Mireben

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Posted: 30th Jan 2010 19:19 Edited at: 30th Jan 2010 19:22

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Do I understand correctly that you want to use the same sprite for both the player paddle and the computer paddle? That will never work. You can use the same image but not the same sprite. The collision is detected by sprite coordinates, so you need two separate sprites, each with their own coordinates.

A few other tips:

You mix the dbSprite and dbPasteSprite calls, only one of these display methods should be necessary. dbSprite displays and positions the sprite, you don't need to paste it again. dbPasteSprite is when you want to control the sprite drawing yourself and that is usually used after hiding the original sprite first.

In dbSpriteCollision, you don't need to repeat the sprite ID numbers twice in reverse order, once is enough.

If you want to use dbSpriteCollision, then be careful with dbOffsetSprite. It displays the image at a different place than the sprite coordinates and I don't know which coordinate set is then used for collision detection... it may be correct but it needs some testing, I never tried.

Never use dbStr like this:

+ Code Snippet

dbText ( 600, 65, dbStr(ballx));

All Dark GDK functions which return a char pointer create a new string in memory every time they are called and if you do not delete the returned string, you create a memory leak. Use sprintf with a char array if you want to display a number in string format.

You use animated sprites like sprite sheets. Although they can be used like that, but this is not their purpose. They are mainly for creating animation and to be played with the dbPlaySprite command. Either create separate images for the sprites (advisable since the paddle sprites have to be separated anyway from each other) or if you want a sprite sheet, you may use dbSetSpriteTextureCoord to set the area of the image which that sprite should display.

General C++ things: Instead of the four "if" statements checking the value of ballmove, you could use a switch statement. Also, variables can (and should) be initialized with a value when they are declared, you don't need to first declare and then assign a value:

+ Code Snippet

int Score = 0;

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Mireben

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Posted: 30th Jan 2010 19:28 Edited at: 30th Jan 2010 19:28

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P.S. If you use two sprites for player paddle and computer paddle, you do not need to check coordinates to see which paddle the ball collided with. You just check collision with both sprites.

And one more coding tip. Instead of this:

+ Code Snippet

// Move ball in a random direction but only Down.
ballmove = dbRnd(3);

// If its going to randomize a number to make it move up then reset it.
if (ballmove == 0) {ballmove = 2;}
if (ballmove == 0) {ballmove = 3;}

(which is wrong anyway because in the last line it should check 1 probably, not a second zero), you can write this:

+ Code Snippet

ballmove = dbRnd(1) + 2;

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Marsh0

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Posted: 30th Jan 2010 19:43

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Thanks for all the advice Mireben, i figured it would save resources or something to make only one sprite for both paddles instead of two. Which is why im pasting the sprite and not just placing it because two paddles work off the same one

. Ill make it into two sprites this will hopefully solve my problem

. Thanks for the random code to i was thinking something like that but never really wrapped my head around it.

Also the paddles will be animated so no problems there. Also could you give me a example of a switch statement if you have some time? i kind of just jumped into c++ and didn't really learn how to do things properly. I think i have seen switch statements but have never written one.

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Mireben

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Posted: 31st Jan 2010 10:24

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Sure, here is an example. This was the original version:

+ Code Snippet

	if (ballmove == 0)
	{
		dbSprite ( 3, ballx = ballx + BallSpeed, bally = bally - BallSpeed, 3 );
	}	

	if (ballmove == 1)
	{
		dbSprite ( 3, ballx = ballx - BallSpeed, bally = bally - BallSpeed, 3 );
	}	

	if (ballmove == 2)
	{
		dbSprite ( 3, ballx = ballx + BallSpeed, bally = bally + BallSpeed, 3 );
	}
	
	if (ballmove == 3)
	{
		dbSprite ( 3, ballx = ballx - BallSpeed, bally = bally + BallSpeed, 3 );
	}

The switch:

+ Code Snippet

		switch (ballmove) 
		{
		case 0:
			dbSprite ( 3, ballx = ballx + BallSpeed, bally = bally - BallSpeed, 3 );
			break;
		case 1:
			dbSprite ( 3, ballx = ballx - BallSpeed, bally = bally - BallSpeed, 3 );
			break;
		case 2:
			dbSprite ( 3, ballx = ballx + BallSpeed, bally = bally + BallSpeed, 3 );
			break;
		case 3:
			dbSprite ( 3, ballx = ballx - BallSpeed, bally = bally + BallSpeed, 3 );
			break;
		}

There are good C++ references at several sites, it's worth to have a look. (A good book may be even better, but the on-line references are very useful and comprehensive too.)

http://www.cplusplus.com/doc/tutorial/
http://msdn.microsoft.com/en-us/beginner/cc305129.aspx
http://www.learncpp.com/

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Marsh0

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Posted: 31st Jan 2010 17:29

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Ah sweet thats handy thanks!

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Dark GDK / Sprite Collision