Check if node is visible on the screen

Question

I currently have a large map that goes off the screen, because of this its coordinate system is very different from my other nodes. This has led me to a problem, because I'm needing to generate a random CGPoint within the bounds of this map, and then if that point is frame/on-screen I place a visible node there. However the check on wether or not the node is on screen continuously fails.

I'm checking if the node is in frame with the following code: CGRectContainsPoint(self.frame, values) (With values being the random CGPoint I generated). Now this is where my problem comes in, the coordinate system of the frame is completely different from the coordinate system of the map.

For example, in the picture below the ball with the arrows pointing to it is at coordinates (479, 402) in the scene's coordinates, but they are actually at (9691, 9753) in the map's coordinates. enter image description here

I determined the coordinates using the touchesBegan event for those who are wondering. So basically, how do I convert that map coordinate system to one that will work for the frame?

Because as seen below, the dot is obviously in the frame however the CGRectContainsPoint always fails. I've tried doing scene.convertPoint(position, fromNode: map) but it didn't work.

Edit: (to clarify some things)

My view hierarchy looks something like this: enter image description here

The map node goes off screen and is about 10,000x10,000 for size. (I have it as a scrolling type map). The origin (Or 0,0) for this node is in the bottom left corner, where the map starts, meaning the origin is offscreen. In the picture above, I'm near the top right part of the map. I'm generating a random CGPoint with the following code (Passing it the maps frame) as an extension to CGPoint:

static func randPoint(within: CGRect) -> CGPoint {
    var point = within.origin

    point.x += CGFloat(arc4random() % UInt32(within.size.width))
    point.y += CGFloat(arc4random() % UInt32(within.size.height))

    return point;
}

I then have the following code (Called in didMoveToView, note that I'm applying this to nodes I'm generating - I just left that code out). Where values is the random position.

let values = CGPoint.randPoint(map.totalFrame)
if !CGRectContainsPoint(self.frame, convertPointToView(scene!.convertPoint(values, fromNode: map))) { 
      color = UIColor.clearColor()
}

To make nodes that are off screen be invisible. (Since the user can scroll the map background). This always passes as true, making all nodes invisible, even though nodes are indeed within the frame (As seen in the picture above, where I commented out the clear color code).

Yup, I'm currently centering the camera on the "unamed" node you see in the center of the screen above. I left that out of the view heirarchy but that would be a node of world. — Aaron

sangony sangony · Accepted Answer · 2015-05-30T15:30:50

Using a worldNode which includes a playerNode and having the camera center on this node, you can check on/off with this code:

float left = player.position.x - 700;
float right = player.position.x + 700;
float up = player.position.y + 450;
float down = player.position.y - 450;

if((object.position.x > left) && (object.position.x < right) && (object.position.y > down) && (object.position.y < up)) {
    if((object.parent == nil) && (object.dead == false)) {
        [worldNode addChild:object];
    }
} else {
    if(object.parent != nil) {
        [object removeFromParent];
    }
}

The numbers I used above are static. You can also make them dynamic:

CGRect screenRect = [[UIScreen mainScreen] bounds];
CGFloat screenWidth = screenRect.size.width;
CGFloat screenHeight = screenRect.size.height;

Diving the screenWidth by 2 for left and right. Same for screenHeight.

Check if node is visible on the screen

2 Answers