Looking for suggestion to move sprite in circular pattern

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Looking for suggestion to move sprite in circular pattern

(8 posts) (7 voices)

Started 2 years ago by Tim
Latest reply from mobilebros

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Tim
Member

I suspect I know the answer to this one and it looks like it'll take some effort...but thought I'd ask anyhow.

I'm just looking for a suggestion on how best to approach moving along a circular or oblong path in a looping fashion. I've been looking at bezier paths but they seem to have an abrupt movement when reversing.

TIA

Posted 2 years ago #
ddeaco
Member

I don't know if this would be the best way of doing it but it should work.

add a small invisible sprite,
parent the sprite you want to rotate to it and offset its position,
rotate the invisible sprite,
if you want to visible sprite to stay upright, correct its orientation based on its parents orientation.

Dave

Posted 2 years ago #
bradparks
Member

The guys at Mobile Bros made an Orbit / RotateAround action... that may do what you want....

http://www.cocos2d-iphone.org/forum/topic/2382

Posted 2 years ago #
Osiris
Member

is this movement via action, or more direct program control? You can always use trig.

Posted 2 years ago #
Tim
Member

Most excellent Brad...just what I was looking for and yes Osiris, this was for an Action. I had tried googling this before posting but kept getting references back to the cocos2d forum so this is a nice external find.

Posted 2 years ago #
ripp
Member

@bradparks, thanks so much for the link! I was already dusting off the trig books when I found this post

Posted 2 years ago #

yarri
Member

Hi, I wrote (but didn't test) a menu alignItemsCircular() method I'll post a patch:

CGPoint ccp_rot( CGPoint v, float ang, float dist )
{
	float X = v.x + dist * sinf( ang * 0.017453f );		//  == PI / 180 deg
	float Y = v.y - dist * cosf( ang * 0.017453f );		//  == PI / 180 deg
	return ccp (X,Y);
}

-(void) alignItemsCircular
{
	return [self alignItemsCircularWithPadding:kDefaultPadding];
}

-(void) alignItemsCircularWithPadding:(float)padding
{
	// padding equals radius
	float angle = 360.f / (float)[children count];

	for(MenuItem* item in children) {
		[item setPosition:ccp_rot(anchorPoint_, angle, padding)];
	}
}

--yarri

Posted 2 years ago #

mobilebros
Moderator
Glad to see our post was useful :) Just wanted to mention that you can also easily create another action based off this action that keeps the node "facing" the center point relative to how it's orientation was at the start of the action. For example this would be useful for something like propeller blades, without the "facing" code the propeller blades would rotate around a point but remain upright. Anywho.... heres the function overloads needed (subclass RotateAround):
```
-(void) start
{
       [super start];
       _startRotation = [(CocosNode*)target rotation];
}

-(void) update: (ccTime) t
{
       [super update:t];

       float rot = _startRotation + -CC_RADIANS_TO_DEGREES(_spanAngle * t);
       [(CocosNode*)target setRotation:rot];
}
```
p.s. _startRotation is a member variable (float)
Posted 2 years ago #

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