I have subclassed UIImageView to create a soccer ball.
The ball bounces and moves along an x & y axis, and depending on where you touch the ball, the ball will move as you'd expect a soccer ball would.
My problem is that I would like to rotate the Ball(UIImageView), but still know the x & y positions from it's original position.
I am rotating it with the following code:
ball.superview.transform = CGAffineTransformMakeRotation(M_PI+(ball.center.x*.015));
ball.transform= CGAffineTransformMakeRotation(M_PI+(ball.center.x*.015));
When I rotate it, the x & y position also rotate. Can I somehow get the x/y distance from the centre of the UIImageView? Any other ideas?
Thanks,
James.
I think if you set the anchor of your CALayer of the UIIMageView to be the center of the UIImageView youll be ok, right now its set to the upper left corner and so are expiriencing the x and y moving.
Why are you rotating the superview also? If you don't do that the center x,y will not be affected.
Why not just use ball.center as the position. This way, rotations will have no effect on the position (assuming your image is correctly centered).
Related
I noticed that in Sprite Kit the coordinate system is flipped.
For example, here is a SKSpriteNode:
SKSpriteNode *car = [SKSpriteNode spriteNodeWithImageNamed:#"car"];
car.position = CGPointMake(0, 0);
[road addChild:car];
The car is positioned in the center of it's parent.
When I set position to:
car.position = CGPointMake(-50, 0);
then it is positioned more to the left.
But when I want to move it down, and increase Y, it moves UP!
car.position = CGPointMake(-50, 20);
In UIKit increasing Y always means something moves down. It feels more logical to me. Is there a way to flip the coordinate system in Sprite Kit?
You can set your scene's yScale property to -1. Everything will render upside down, but you can also set the yScale property for each node to -1, which will cause them to render right side up.
You could also make a class category and create a property called invertedPosition with a custom getter/setter that inverts the default position property.
Sprite Kit uses a coordinate orientation that starts from the bottom left corner of the scene (0,0), and the values increase as you move to the right (increasing x) and up (increasing y).
I have the following view where I'm using a pan gesture in the upwards or downwards direction to rotate it positively or negatively:
I'm wondering, is there a mathematical equation to precisely covert the amount panned to the amount it should be rotated so the timing is correct to keep the users finger on the view while it is rotating? For instance, if the pan translation comes back as 1, what would the proper amount be to rotate it?.
There are a few details you need to provide to give a meaningful answer:
Are you rotating the view about its centre (the default) or is there an anchor point?
Since the view is rotating, while the touch is moving strictly vertically in the superview, what's the expected behaviour as the view rotates further away from the vertical line defining the pan?
Is there a reason you're using a pan gesture instead of a rotation gesture, or even just direct touch tracking? It seems like it creates more problems than it solves.
I'm going to assume the view is rotating about its centre for the sake of simplicity, and I'll use a pan starting on the right side of the view as an example, with the rotation not exceeding ±90°. Here are two options:
Movement up and down translates linearly to the angle of rotation, i.e., a pan of a given distance rotates the view the same amount, no matter where the pan starts. In that case, you need to decide what the top and bottom limits of the pan are. They might be the bounds of the superview. Regardless, you want to convert the distance travelled in the Y direction to a value between -1 and 1, where -1 represents the bottom limit and 1 represents the top limit. Something like 2 * (dy / superview.bounds.size.height - 0.5). Multiply that by π/2 (M_PI_2 in math.h) to scale from the range [-1, 1] to the range [-π/2, π/2] and you've got the angle to add/subtract from the view's rotation at the beginning of the gesture.
The view tracks the touch so that its right edge is always "pointed at" the touch. In this case, pan isn't terribly useful because you only need the location of the touch in the superview, not the distance travelled. Calculate dx and dy as the difference in x and y coordinates from the view's centre to the touch location. Then calculate atan2(dy, dx) and you've got the absolute angle of rotation for the view.
I hope this puts you on the right track.
The answer is the angle would be panAmount.y / rectangleWidth.
Here is proof: https://math.stackexchange.com/questions/322694/angle-of-rotated-line-segment
I am new to Cocos2D on iPhone. I see that Cocos2D uses a coordinate axis where 0,0 is at the bottom left corner and X positives are to the right and Y positives up.
Now I have created a sprite and added several sprites as subsprites of this one. For my surprise the subsprites appear mirrored in Y!!! The point 10,10 will be on the upper left corner of the sprite!!!
I can simply flip the sprite in Y to make it follow the same screen coordinate, but then the content will be reversed.
Is this a bug or what?
thanks.
Without seeing any example code is a shot in the dark, but I think you need to use Anchor points.
Each sprite has an anchor point of x, y.
ccp(0.5f, 0.5f) would be the center of the sprite.
(0,0) is the bottom left....(1.0f,1.0f) is top right etc.... Over 1.0 goes outside the sprite.
Child nodes (CCSprite) will use their anchor point on the parent node coordinates.
MySprite.anchorPoint = ccp(0.5f,0.5f);
I am trying to get a each position of a sprite(curve),not only the center point,from starting point to end point.My sprite will rotate by 30deg when i tap on the screen.so i can't use sprite.position.x-sprite.contentSize.width/2 or some thing like that.Is there any way to get the position of a sprite or is there any other way to do this.
My need is i have different curve path.when i join those curve path,the new sprite should move along the curve path.
I think you are looking for convertToWorldSpace function of CCNode.
If I correctly understood you, you want to get sprite coord(not center, bottom left corner) rotated by 30 degrees? For x axis use formula: newX = X + cos(30) * pathLong. For y use the same but replace cos by sin and x by y of course :).
When changing the center point of an 10 degrees rotated view, the specified coordinates for the center point will not match the coordinate system of the superview.
As an example, when you want to go straight up by y - 50, and no horizontal movement (i.e. x = theRotatedView.center.x), the shift in y-direction will be rotated. The view will go up and right, and not just up.
The rotation is done on the view, not on the layer.
I could wrap it in a superview that does the movement, while the subview does the rotation. Then I had no problems with converting. But maybe there is some simple solution. I just want to move the center of an rotated view as if the view was not rotated, i.e. when wanting y to be decremented by 10, just do so without worrying about the rotated coordinates. Are there any methods or functions for converting between the coordinate systems, so that I can just specify the center point coordinates in superview coordinates and it will just be right when applying these to the rotated view's center property?
Look at the CGAffineTransform methods, such as CGAffineTransformMake, for an easier way to generate the transforms you need. You can combine rotation and translation in one matrix.
You can multiply your coordinates by a transformation matrix. This puts your coordinates into your parent view's "coordinate space". You can also use the inverse matrix of the parent view to take coordinates that are in the parent view and return them to "world space".
http://en.wikipedia.org/wiki/Rotation_matrix
Read further down the page for pseudo-code examples.