反回曲线上一定距离的点（默认从起点开始计算）
pCurve:曲线指针，dist：距离，point：要返回的点
Adesk::Boolean isGotoNext true:沿着正向寻找，false：沿着反方向寻找
static void GetPtAtDistOnCurve(const AcGeCurve2d* pCurve,const AcGePoint2d& ptInput,double dist,AcGePoint2d& point,Adesk::Boolean isGotoNext)
{
if(pCurve == NULL)
{
return;
}
AcGePoint2d ptS;
ptS = ptInput;
double pa = 0.0;
double datumParam = 0.0;
//Adesk::Boolean posParamDir = Adesk::kTrue;
datumParam = pCurve->paramOf(ptS);
pa = pCurve->paramAtLength(datumParam,dist,isGotoNext);
point = pCurve->evalPoint(pa);
}
