point.h

演示一个火车头沿着轨道运行的动画。轨道可自定义(用鼠标绘制)

#ifndef MY_POINT_H
#define MY_POINT_H
/* file: point.h
*/

#include <math.h>

typedef enum{FALSE, TRUE} BOOL; 

typedef struct
{
	int x;
	int y;
}POINT;

/* 求a,b点间距离 */
static float Distance(POINT* a, POINT* b)
{
	long x = a->x - b->x;
	long y = a->y - b->y;

	return sqrt(x*x+y*y);
}/*end Distance*/

/* 求∠abc */
static float Angle(POINT* a, POINT* b, POINT* c)
{
	float th;
	long xa = a->x - b->x;
	long ya = a->y - b->y;
	long xc = c->x - b->x;
	long yc = c->y - b->y;
	long	x=xa*xc+ya*yc;
	double	y=xc*ya-xa*yc;

	if( x == 0 )
		{
		return (y>0.0)?M_PI_2:(-M_PI_2);
		}
	else	{
		th=atan(y/x);
		if( x<0 )
			{
			if( th<0.0 )
				{
				th+=M_PI;
				}
			else	{
				th-=M_PI;
				}/*end if*/
			}/*end if*/
		return th;
		}/*end if*/
}/*end Angle*/

/* 求与向量pf->pt 同向的单位向量（*px, *py）*/
static void GetDirection(POINT* pf, POINT* pt, float* px, float* py)
{
	double dx = pt->x - pf->x;
	double dy = pt->y - pf->y;
	double m=1.0/sqrt(dx*dx+dy*dy);

	*px=dx*m;
	*py=dy*m;
}/*end GetDirection*/

/* 将点 p 绕原点旋转 arctan(dy/dx) 度，（dx,dy）为单位向量 */
static void Rotate(POINT* p, float dx, float dy)
{
	POINT t=*p;

	p->x = 0.5+t.x*dx-t.y*dy;
	p->y = 0.5+t.y*dx+t.x*dy;
}/*end Rotate*/

#endif /*define MY_POINT_H*/