A fast, easy to use, free, and community supported 2D game engine
bsharp42
Member
Hello, new here and new to the framework/cocoa/obj-c :)
Anyway, I have this sprite image.
Right now, when the sprite image goes off screen, as in moves towards the edge of the screen and keeps going. In other words, it doesn't bounch off the wall (screen boundary).
I want to make it so that when it goes off the screen towards the right side of the screen, i want it to show up on the left screen and continue doing whatever its suppose to do.
Is there an easy way to do this ?
The easiest way is to compare your sprite's position to the edges of the screen and reset to the opposite side. For example
// assuming landscape
if(sprite.position.x > 480) sprite.position.x = 0;
if(sprite.position.x < 0) sprite.position.x = 480;
I hope that helps,
Serban
bsharp42
Member
To give more information.
Lets say I have a Sprite that goes around in random location on the screen.
It is using several bezierBy functions to generate semi-random movement/speed.
So it is important that when it passes through the boundary and appear on the otherside, it keeps the current movement pattern.
Codemattic
Moderator
"error: lvalue required as left operand of assignment"
bsharp42 - I make the same mistake all the time. I think its bc position is a struct not a pointer to an object, so sprite.position returns a copy of the struct.
"What if I have, lets say, 40 of these sprites moving at a relatively fast speed"
Doubt it. Write the code however is easiest - worry about optimizing later. The bottlenecks are often not where you thought at the beginning of the project.
good luck!
You're right Codemattic. Position is a property setup in CocosNode.h as @property(readwrite,assign) CGPoint position; and will return a CGPoint by value. The snippet I provided was meant to be pseudo code.
@bsharp42, the problem you describe is a bit harder. BezierBy (or any other part of cocos2d) doesn't have any notion/understanding of screen wrapping. That's something you're going to have to take care of yourself.
There might be a "better" way, but the simplest approach that comes to mind is to have an invisible, phantom sprite that gets moved around by BezierBy. Every frame you query the phantom sprite's position (which is potentially way off screen), you map the off screen coordinates to on screen coordinates, and set the position of a visible sprite.
Here's the mapping:
xwrapped = phantomSprite.position.x % screen_width;
ywrapped = phantomSprite.position.y % screen_height;
visibleSprite.position = CGPointMake(xwrapped, ywrapped);
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