也围绕自身中心旋转对象

Question

star.rotation += star.speed;
float angleRadian = star.rotation * PI_DIV_180;
star.position = ccp(windowSize.width/2 + (star.radius * sinf(angleRadian)), windowSize.height/2 + (star.radius * cosf(angleRadian)));

上面是调用每一帧时沿窗口中心点旋转star子画面。锚点是星体的中心。如何使星星也沿着自心旋转？

Answer 1

您想要围绕彼此旋转的对象，以及沿自己的轴旋转/旋转？像这样的东西？

旋转测试.h

@interface RotationTest : CCLayer
{
    CCSprite *star;
    CCSprite *planet;
    CCSprite *satellite;
    float dist_star_planet;
    float dist_planet_satellite;
    float relative_angle_star_planet;
    float relative_angle_planet_satellite;
}
@end

旋转测试.m

#import "RotationTest.h"
@implementation RotationTest
-(id) init
{
    if( (self=[super init]))
    {
        CGSize s = [[CCDirector sharedDirector] winSize];
        star = [CCSprite spriteWithFile:@"Icon.png"];
        planet = [CCSprite spriteWithFile:@"Icon.png"];
        satellite = [CCSprite spriteWithFile:@"Icon.png"];
        [self addChild: star];
        [self addChild:planet];
        [self addChild:satellite];
        star.position = ccp(s.width / 2.0f, s.height / 2.0f);
        planet.position = ccpAdd(star.position, ccp(100.0f, 0.0f));
        satellite.position = ccpAdd(planet.position, ccp(50.0f, 0.0f));
        star.scale = 0.5f;
        planet.scale = 0.35f;
        satellite.scale = 0.2f;
        dist_star_planet = ccpDistance(planet.position, star.position);
        dist_planet_satellite = ccpDistance(satellite.position, planet.position);
        relative_angle_star_planet = 0.0f;
        relative_angle_planet_satellite = 0.0f;
        [self scheduleUpdate];
    }
    return self;
}
-(void) update:(ccTime) dt
{
    star.rotation += 1.0f; // degs
    planet.rotation -= 1.0f;
    satellite.rotation += 2.0f;
    relative_angle_star_planet += 0.01f; // rads
    relative_angle_planet_satellite -= 0.01f;
    planet.position = ccpAdd(star.position, ccp(dist_star_planet * sinf(relative_angle_star_planet), dist_star_planet * cosf(relative_angle_star_planet)));
    satellite.position = ccpAdd(planet.position, ccp(dist_planet_satellite * sinf(relative_angle_planet_satellite), dist_planet_satellite * cosf(relative_angle_planet_satellite)));
}
@end

Answer 2

旋转

将始终围绕(0,0)旋转，因此您只需平移p要成为中心的点，就可以(0,0)的角度旋转，然后平移回来！

编辑：

因此，如果您想旋转轴，第一个是屏幕的中心p，第二个是星星q的中心，旋转角度P和Q。

Set Star to (0,0) rotate by Q
Translate Star by the distance you want around p
Rotate by P
Translate (0,0) to p