更改 Sprite Anchorpoint 而不移动它？

Question

我正在尝试更改我的 Sprite 锚点，以便可以在 0.0f,0.0f 锚点上旋转。起初我的对象是在默认锚点（0.5f，0.5f）处旋转。但是后来我需要它在 0.0,0.0 AnchorPoint 上旋转。

问题是我无法更改锚点并相应地更改位置，因此它保持在同一位置，而对象似乎不会快速移动并重新定位到其原始点。

有没有一种方法可以一次设置我的 Sprite 的锚点和位置，而不需要它移动？谢谢。

-奥斯卡

Answer 1

Cocos2d-x + 固定比例

YourClass.h

virtual cocos2d::Vec2 positionFromSprite(cocos2d::Vec2 newAnchorPoint, cocos2d::Sprite *sprite);

YourClass.m

Vec2 YourClass::positionFromSprite(Vec2 newAnchorPoint, cocos2d::Sprite *sprite) {
    Rect rect = sprite->getSpriteFrame()->getRect();
    Vec2 oldAnchorPoint = sprite->getAnchorPoint();
    float scaleX = sprite->getScaleX();
    float scaleY = sprite->getScaleY();

    Vec2 newPoint = Vec2(rect.size.width * newAnchorPoint.x * scaleX, rect.size.height * newAnchorPoint.y * scaleY);
    Vec2 oldPoint = Vec2(rect.size.width * oldAnchorPoint.x * scaleX, rect.size.height * oldAnchorPoint.y * scaleY);

    Vec2 position = sprite->getPosition();

    position.x -= oldPoint.x;
    position.x += newPoint.x;

    position.y -= oldPoint.y;
    position.y += newPoint.y;

    return position;
}

Answer 2

我需要这个几次，并决定为 CCNode 做一个扩展，测试了一下，似乎工作正常。对某些人来说真的很有用:)

它在 1.x 中经过测试，但在 2.x 中也应该可以正常工作。支持转换节点和高清。

只需将它添加到您的项目并在需要时导入 - 它将添加到从 CCNode 派生的所有类中。 (CCSprite, CCLayer)

界面

#import "cocos2d.h"

@interface CCNode (Extensions)

// Returns the parent coordinate for an anchorpoint. Useful for aligning nodes with different anchorpoints for instance
-(CGPoint)positionOfAnchorPoint:(CGPoint)anchor;

// As above but using anchorpoint in points rather than percentage
-(CGPoint)positionOfAnchorPointInPoints:(CGPoint)anchor;

//Sets the anchorpoint, to not move the node set lockPosition to `YES`. Setting it to `NO` is equal to setAnchorPoint, I thought this would be good for readability so you always know what you do when you move the anchorpoint
-(void)setAnchorPoint:(CGPoint)a lockPosition:(BOOL)lockPosition;

@end

实施

#import "CCNode+AnchorPos.h"

@implementation CCNode (Extensions)

-(CGPoint)positionOfAnchorPoint:(CGPoint)anchor
{
    float x = anchor.x * self.contentSizeInPixels.width;
    float y = anchor.y * self.contentSizeInPixels.height;

    CGPoint pos = ccp(x,y);

    pos = CGPointApplyAffineTransform(pos, [self nodeToParentTransform]);

    return ccpMult(pos, 1/CC_CONTENT_SCALE_FACTOR());
}

-(CGPoint)positionOfAnchorPointInPoints:(CGPoint)anchor;
{
    CGPoint anchorPointInPercent = ccp(anchor.x/self.contentSize.width, anchor.y/self.contentSize.height);
    return [self positionOfAnchorPoint:anchorPointInPercent];
}

-(void)setAnchorPoint:(CGPoint)a lockPosition:(BOOL)lockPosition
{
    CGPoint tempPos = [self positionOfAnchorPoint:a];
    self.anchorPoint = a;

    if(lockPosition)
    {
        self.position = tempPos;
    }
}

@end

Answer 3

我在别处找到了一个 UIView 的解决方案，并为 cocos2d 重写了它：

- (void)setAnchorPoint:(CGPoint)anchorPoint forSprite:(CCSprite *)sprite
{
    CGPoint newPoint = CGPointMake(sprite.contentSize.width * anchorPoint.x, sprite.contentSize.height * anchorPoint.y);
    CGPoint oldPoint = CGPointMake(sprite.contentSize.width * sprite.anchorPoint.x, sprite.contentSize.height * sprite.anchorPoint.y);

    newPoint = CGPointApplyAffineTransform(newPoint, [sprite nodeToWorldTransform]);
    oldPoint = CGPointApplyAffineTransform(oldPoint, [sprite nodeToWorldTransform]);

    CGPoint position = sprite.position;

    position.x -= oldPoint.x;
    position.x += newPoint.x;

    position.y -= oldPoint.y;
    position.y += newPoint.y;

    sprite.position = position;
    sprite.anchorPoint = anchorPoint;
}

Answer 4

这是一个很好的问题，我还不知道完整的答案。

您可能已经注意到，在不影响缩放和旋转的情况下无法更改锚点。

对于缩放的精灵：

您必须同时更改精灵的锚点和位置。见this question for a hint

对于旋转的精灵：

直觉说您需要同时更改锚点、旋转和位置。 （我不知道如何计算。）

注意：我还在学习图形编程，所以我还不能 100% 计算这些东西。