Touches in a non Square Object « cocos2d for iPhone

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Touches in a non Square Object

(9 posts) (4 voices)

Started 2 years ago by cbakker
Latest reply from cbakker

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cbakker
Member

Seems everything i find uses CGRect for touch detection. Is there any way to use a non square object (Hexagon, Octogon, Circle) for touch detecting like in the code below?

- (CGRect) rect
{
float x = [self position].x - [self contentSize].width/2;
float y = [self position].y - [self contentSize].height/2;
float h = [self contentSize].height;
float w = [self contentSize].width;
return CGRectMake(x,y,w,h);
}

The problem is if everything is squares on close objects clicks happen on multiple items.

-- Thanks

Posted 2 years ago #
Codemattic
Moderator

Axis aligned rects are very easy to hittest. Circles are very easy to hittest. Everything else gets much harder. Convex polys are probably next easiest, and then concave polys.

Posted 2 years ago #
ob1
Member

You can also do a alpha or mask hitTest. Pretty easy and accurate.

This method has its own problems though.

Posted 2 years ago #
jotajota
Member

@ob1 do you mean is possible to detect if a touch happened on a transparent pixel of a Sprite? how?!

Posted 2 years ago #
ob1
Member

I guess that if you have the sprite you can do something with the texture. That's how they do it in UIKit (it causes problems the other way around, i.e. when you want the whole sprite to be touch sensitive and not only the opaque part). Maybe someone more knowledgeable than me can chime in.

Otherwise, add a bitmask to your sprite.

Posted 2 years ago #
cbakker
Member

Thanks Codemattic for sending me in the right direction. Works like a charm. Below is what i used if anyone else needs it.

Used this Method to figure the distance between the middle of the CGRect and the ClickPoint.

- (CGFloat) DistanceBetweenTwoPoints: (CGPoint)startPoint andEndPoint: (CGPoint)endPoint
{
CGFloat x = endPoint.x - startPoint.x;
CGFloat y = endPoint.y - startPoint.y;

return sqrt(x * x + y * y);
}

Then used in another method to figure if the touch was inside the circle.:

CGFloat objPositionCenterX = CGRectGetMidX([obj rect]);
CGFloat objPositionCenterY = CGRectGetMidY([obj rect]);

CGFloat clickPositionX = pos.x;
CGFloat clickPositionY = pos.y;

CGPoint startingPoint = CGPointMake(objPositionCenterX, objPositionCenterY);
CGPoint endingPoint = CGPointMake(clickPositionX, clickPositionY);
CGFloat distance = [obj DistanceBetweenTwoPoints:(CGPoint)startingPoint andEndPoint:(CGPoint)endingPoint];

if (distance > 16)
{
return NO;
}
else
{
return YES;
}

Thanks Again

Posted 2 years ago #
ob1
Member

You can probably do:

- (CGFloat) DistanceBetweenTwoPoints: (CGPoint)startPoint andEndPoint: (CGPoint)endPoint
{
CGFloat x = endPoint.x - startPoint.x;
CGFloat y = endPoint.y - startPoint.y;

return (x * x + y * y);
}

...
if (distance > 16*16)
{
return NO;
}

Saves the cost of the square root, that's what I do in my code. I don't know if sqrt is that expensive though.

Posted 2 years ago #
Codemattic
Moderator

cbakker, you may want to check out the CGPointExtension.h and CGPointExtension.m, it has ccpLengthSQ and ccpLength as well as some other vector/point math you may find useful!

Posted 2 years ago #
cbakker
Member

Thanks for the tip ill check that out.

Posted 2 years ago #

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