The Call

I know this isn't exactly what comments are for, but my membership is pending on Greenfoot-Discuss and I have a quick programming question. I'm currently making a Super Mario Brothers games, but I'm getting tired of having the levels only as big as the world (640, 480). I'm working on making the world scroll. Here's what's happening. When the player is past the middle of the world, and he's moving right, the background image, and mask image, should scroll with him. As for moving leftwards. They DO scroll with him, but they get out of sync. Here's the code snippet. Player extends Actor //mworld is equal to getWorld() //x is equal to getX() //isGround is true if the color BLACK is found on the mask at the given location, relative to the Player public void act() { if(mworld.Scrolling==true & x >= 640/2 & xs >0 && !mworld.isGround(getX()+14, getY())) { if(scrollPosition <= mworld.mask.getWidth()) { scrollPosition += scrollSpeed; maskImage = getMaskImage(640, 480); //see getMaskImage(int, int) and getBackgroundImage(int, int) scrollSpeed = xs; //xs is the speed of the Players movement } paint(-scrollPosition); //see paint(int) } if(mworld.Scrolling==true & x <= 640/2 & xs <0 && !mworld.isGround(getX()-14, getY())) { if(scrollPosition >= -mworld.mask.getWidth()) { scrollPosition -= scrollSpeed; maskImage = getMaskImage(640, 480); scrollSpeed = -xs; //xs is the speed of the Players movement } paint(-scrollPosition); } } /** * Paints an image. */ private void paint(int position) { mworld.background.drawImage(scrollingImage, position, 0); mworld.mask.drawImage(maskImage, position, 0); if(position > 0) { mworld.background.drawImage(scrollingImage, position - scrollingImage.getWidth(), 0); mworld.mask.drawImage(maskImage, position - maskImage.getWidth(), 0); } else { mworld.background.drawImage(scrollingImage, position + scrollingImage.getWidth(), 0); mworld.mask.drawImage(maskImage, position + maskImage.getWidth(), 0); } } /** * Returns a background image with the given dimensions. */ private GreenfootImage getScrollingImage(int width, int height) { GreenfootImage Image = new GreenfootImage(width, height); for(int l = 0; l < width; l += mworld.background.getWidth()) { for(int m = 0; m < height; m += mworld.background.getHeight()) { Image.drawImage(mworld.background, l, m); } } return Image; } /** * Returns a mask image with the given dimensions. */ private GreenfootImage getMaskImage(int width, int height) { GreenfootImage image = new GreenfootImage(width, height); for(int n = 0; n < width; n += mworld.mask.getWidth()) { for(int o = 0; o < height; o += mworld.mask.getHeight()) { image.drawImage(mworld.mask, n, o); } } return image; } Of course I can't take credit for all of that programming. Anyways. You seem to know your way around so if you can point out what I'm doing wrong or an alternative to scroll the background and mask image simultaneously, please let me know. It's not a problem if you don't know, or don't want to help. Thanks bourne

Also, in your game here, the "a" and "d" keys seem to make the Player run faster than the "w" and "s" keys or any combination.

Haha, I fixed my problem, the world was scrolling then adding player location to it. Disregard my desperate plea for help. Thanks anyways :)

Ha well, glad you got it fixed. And regarding the player running faster in my game, it just looks that way because running left and right is more pixels wide because the tiles are farther apart on screen. But it takes the same time to run to any surrounding tile. I suppose it should take slightly longer to run diagonally since its a farther distance on a 2d plane.

Okay. Also, I was just wondering, in "The Call" when stationary actors are located off the edge of the applet (such as doors and whatnot) they must have a set location. When the Player moves, does it increment an "x" and "y" variable telling everything whether to appear or not? I'll examine your source code because I'm not sure if that made perfect sense... I ask because I have an exit door in my game, positioned about 500 pixels off to the right of the worlds edge and I need to find a method to make it enter the screen when the player gets near enough. I'm new to scrolling games.

Well with Greenfoot 2.0 you can add actors off the screen. And will appear on screen as it moves left (heading towards the viewing screen) as you would 'move' right. And as for my game, objects that appear on screen are drawn as images on a single actor instead of individual actors.