CODEWITHSUNDEEP
iosiphonesprite-kitfloating-point-conversion
Marcus
Marcus

Reputation: 95

Converting between coordinate spaces SpriteKit

I have a node with the shape of a box in a scene. The shape node should have its own coordinate space, so if I declare a point at (100,100) in the nodes coordinate space and rotate the box pi/4 rad the point should change in the scenes coordinate space.

My problem is I cant get this to work, I'm using the following code to convert a point in the nodes coord space to the scenes coord space, the placement of the node is 200,200 in the scene:

startPointInNodeSpace = CGPointMake(0, size.height/2);
CGPoint start = [self.scene convertPoint:CGPointMake(startPointInNodeSpace.x, startPointInNodeSpace.y) fromNode:self.parent];
CGPoint end = [self.scene convertPoint:CGPointMake(startPointInNodeSpace.x, startPointInNodeSpace.y + 100) fromNode:self.parent];
NSLog(@"start position in node: (%f,%f)\nend position in node: (%f,%f)",startPointInNodeSpace.x,startPointInNodeSpace.y,startPointInNodeSpace.x,startPointInNodeSpace.y + 100);
NSLog(@"start position in scene: (%f,%f)\nend position in scene: (%f,%f)",start.x,start.y,end.x,end.y);

The code is inside a subclass of SKSpriteNode.

My log:

start position in node: (0.000000,20.000000)
end position in node: (0.000000,120.000000)
start position in scene: (0.000000,20.000000)
end position in scene: (0.000000,120.000000)

As you can see it is not converting the points at all but I dont know what I am doing wrong.

Visual Illustration of what I want to achieve:

Conversion

Upvotes: 0

Views: 1816

Answers (2)

Marcus
Marcus

Reputation: 95

I was using the following code in the scene to rotate the node:

SKAction *rotation = [SKAction rotateByAngle: M_PI/4.0 duration:0];
[MYNODE runAction: rotation];

When I changed it to this inside the nodeclass instead it worked as expected:

self.zRotation = M_PI/4;

Upvotes: 0

Austin
Austin

Reputation: 5655

I think the problem is that you're converting from self.parent instead of self — the node's parent is the scene, so there's no conversion to be done. Try converting from self instead:

startPointInNodeSpace = CGPointMake(0, size.height/2);
endPointInNodeSpace = CGPointMake(startPointInNodeSpace.x, startPointInNodeSpace.y + 100);
CGPoint start = [self.scene convertPoint:startPointInNodeSpace fromNode:self];
CGPoint end = [self.scene convertPoint:endPointInNodeSpace fromNode:self];

(Note that you can just pass startPointInNodeSpace into the method, rather than creating an identical point. Structs are copied by value, so the method can't mutate your variable.)

Upvotes: 2

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