Box2D计算轨迹

Question

我试图使物理体以随机速度的随机位置生成，以达到目标。我从使用Chipmunk在Box2D中运行的网络中收集并稍微修改了此代码

+ (CGPoint) calculateShotForTarget:(CGPoint)target from:(CGPoint) launchPos with:(float) velocity
{
    float xp = target.x - launchPos.x;
    float y = target.y - launchPos.y;
    float g = 20;
    float v = velocity;
    float angle1, angle2;

    float tmp = pow(v, 4) - g * (g * pow(xp, 2) + 2 * y * pow(v, 2));

    if(tmp < 0){
        NSLog(@"No Firing Solution");
    }else{
        angle1 = atan2(pow(v, 2) + sqrt(tmp), g * xp);
        angle2 = atan2(pow(v, 2) - sqrt(tmp), g * xp);
    }

    CGPoint direction = CGPointMake(cosf(angle1),sinf(angle1));
    CGPoint force = CGPointMake(direction.x * v, direction.y * v);

    NSLog(@"force = %@", NSStringFromCGPoint(force));
    NSLog(@"direction = %@", NSStringFromCGPoint(direction));

    return force;
}

问题是我不知道如何将其应用于我的程序，我的重力为-20，但为g投入20，而较低的速度像10的v速度为v，除了“没有射击解决方案”，我什么都没有。

我究竟做错了什么？

Answer 1

较低的速度为10永远不会起作用。弹丸没有足够的动力来行驶距离。

计算中的错误是，除了像素中的距离计算外，所有内容均为米！

将代码更改为此修复了我得到的疯狂速度：

+ (CGPoint) calculateShotForTarget:(CGPoint)target from:(CGPoint) launchPos with:(float) velocity
{
    float xp = (target.x - launchPos.x) / PTM_RATIO;
    float y = (target.y - launchPos.y) / PTM_RATIO;
    float g = 20;
    float v = velocity;
    float angle1, angle2;

    float tmp = pow(v, 4) - g * (g * pow(xp, 2) + 2 * y * pow(v, 2));

    if(tmp < 0){
        NSLog(@"No Firing Solution");
    }else{
        angle1 = atan2(pow(v, 2) + sqrt(tmp), g * xp);
        angle2 = atan2(pow(v, 2) - sqrt(tmp), g * xp);
    }

    CGPoint direction = CGPointMake(cosf(angle1),sinf(angle1));
    CGPoint force = CGPointMake(direction.x * v, direction.y * v);

    NSLog(@"force = %@", NSStringFromCGPoint(force));
    NSLog(@"direction = %@", NSStringFromCGPoint(direction));

    return force;
}