Question

我一直在研究旋转功能。每个循环，这些点随着滑动中心移动到旋转中心。它取决于获取中心和旋转点之间距离的函数：

struct Vector3F
{
    float x, y, z;
};

inline float GetDistance3FX_inline(Vector3F* v1, Vector3F* v2) 
{ 
    return v1->x - v2->x; 
}

inline float GetDistance3FZ_inline(Vector3F* v1, Vector3F* v2) 
{ 
    return v1->z - v2->z; 
}

实际的旋转功能，工作：

void Rotate3FY(Vector3F* point, Vector3F* center, float rad)
{
    float x = GetDistance3FX_inline(point, center);
    float z = GetDistance3FZ_inline(point, center);
    point->x = x * cos(rad) - z * sin(rad) + center->x;
    point->z = z * cos(rad) + x * sin(rad) + center->z;
}

不的功能：

void Rotate3FY(Vector3F* point, Vector3F* center, float rad)
{
    point->x = GetDistance3FX_inline(point, center) * cos(rad) - GetDistance3FZ_inline(point, center) * sin(rad) + center->x;
    point->z = GetDistance3FZ_inline(point, center) * cos(rad) + GetDistance3FX_inline(point, center) * sin(rad) + center->z;
}

我不知道这两者之间存在什么逻辑差异。感谢您的任何建议。

Answer 1

在您更新point->x时的第二个功能中，您正在更改point的属性。因此，当您在设置point->z期间再次调用相同的功能时，point->x的值已经更改。

void Rotate3FY(Vector3F* point, Vector3F* center, float rad)
{
    point->x = GetDistance3FX_inline(point, center) * cos(rad) - GetDistance3FZ_inline(point, center) * sin(rad) + center->x;
    // point is now different to what it was at the start because you just 
    // changed is x member!!!!!!!
    point->z = GetDistance3FZ_inline(point, center) * cos(rad) + GetDistance3FX_inline(point, center) * sin(rad) + center->z;
}

在第一个函数中，您需要在修改point之前将所需的值存储在单独的变量中。

旋转功能奇怪的行为

1 个答案: