Question

我正在使用Box2D在Objective C中创建一个汽车游戏。我想根据CCSprite（转向）旋转来旋转车轮。

所以为此，我成功地根据触摸设置了CCSprite Steering的角度。但是当我试图获得Steer旋转的价值时，它并没有得到完美的结果，尽管Steer旋转完美。但Radian Angle值有时并不完美。 所以我无法按照转向旋转

旋转车轮

我的代码是设置转向角度如下

触摸开始，设置起始角度

-(void)getAngleSteer:(UITouch *) touch
{
    CGPoint location = [touch locationInView: [touch view]];
    location = [[CCDirector sharedDirector] convertToGL: location];
    float adjacent = steering.position.x - location.x;
    float opposite = steering.position.y - location.y;

    self.startAngleForSteer = atan2f(adjacent, opposite);
}

触摸移动，移动转向和设置轿厢角度

-(void)rotateSteer:(UITouch *) touch
{
    CGPoint location = [touch locationInView: [touch view]];
    location = [[CCDirector sharedDirector] convertToGL: location];

    float adjacent = steering.position.x - location.x;
    float opposite = steering.position.y - location.y;

    float angle = atan2f(adjacent, opposite);
    angle = angle - self.startAngleForSteer;
    steering.rotation = CC_RADIANS_TO_DEGREES(angle);

    //Main issue is in below line
    NSLog(@"%f %f", angle, CC_RADIANS_TO_DEGREES(angle));       
    if(angle > M_PI/3 || angle < -M_PI/3) return;
    steering_angle = -angle;//This is for Box2D Car Angle
}

这是Log，当移动Steer时，逆时针方向

-0.127680 -7.315529
-0.212759 -12.190166
-0.329367 -18.871363
5.807306 332.734131    // Why is 5.80 cuming just after -0.32 it should be decrease.
5.721369 327.810303
5.665644 324.617462

Answer 1

终于得到了答案。感谢Box2D论坛（http://box2d.org/forum/viewtopic.php?f=5&t=4726）

对于Objective C，我们必须将角度标准化，如下面的函数。

-(float) normalizeAngle:(float) angle
{
    CGFloat result = (float)((int) angle % (int) (2*M_PI));

    return (result) >= 0 ? (angle < M_PI) ? angle : angle - (2*M_PI) : (angle >= -M_PI) ? angle : angle + (2*M_PI);
}

在条件检查M_PI / 3之前调用它

steering.rotation = CC_RADIANS_TO_DEGREES(angle);
angle = [self normalizeAngle:angle];//This is where to call.
if(angle > M_PI/3 || angle < -M_PI/3) return;
steering_angle = -angle;

Box2d Objective-C中的弧度角检查

1 个答案: