[ARX]随点画了N边形，请问怎么得到这个N边形的面积

uusky

随点画了个N边形，请问怎么得到这个N边形的面积，好象可以通过这种方法得到：
AcDbPolyline * pPline ;
double area=0;
pPline->getArea(area);
acutPrintf("\n面积为 %.3f\n",area);
可是我不知道如何添加？（加了几次了都取不到面积 很郁闷 ）
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include

ads_point pt1[512];
AcGePoint3d pt[512];
int NodeNumCount;
void area()
{
int i=0;
acedGetPoint(NULL,"\n请选择起始点:",asDblArray(pt[0]));

do {
acedGetPoint(asDblArray(pt),"\n拾取下一点:",asDblArray(pt[i+1]));
AcDbLine *pLine=new AcDbLine(pt,pt[i+1]);
AcDbBlockTable *pBlkTable2;
acdbHostApplicationServices()->workingDatabase()
->getSymbolTable(pBlkTable2, AcDb::kForRead);
AcDbBlockTableRecord *pBlockTableRecord;

pBlkTable2->getAt(ACDB_MODEL_SPACE, pBlockTableRecord,
AcDb::kForWrite);
pBlkTable2->close();

AcDbObjectId lineId=AcDbObjectId::kNull;
pBlockTableRecord->appendAcDbEntity(lineId, pLine);
pBlockTableRecord->close();
pLine->close();
changepoint(pt1[i+1],pt[i+1]);//转换点的类型
changepoint(pt1[0],pt[0]);//转换点的类型
i++;
NodeNumCount=i;//取得边数
}
while((Equal_Points (pt1, pt1[0]))==0);//起始点=终点时结束循环
}

int Equal_Points (const ads_point p1, const ads_point p2) //判断两点是否为同一点
{
// 指定误差范围
const ads_real Equality_Margin = (ads_real)0.0001;
int c ;
for (c = X ; c <= Z ; c++)
{
if (fabs(p1[c] - p2[c]) > Equality_Margin)
{return (0) ;}
}
{
AcDbLine *pLine=new AcDbLine(pt[0],pt[NodeNumCount]);
AcDbBlockTable *pBlkTable2;
acdbHostApplicationServices()->workingDatabase()
->getSymbolTable(pBlkTable2, AcDb::kForRead);

AcDbBlockTableRecord *pBlockTableRecord;

pBlkTable2->getAt(ACDB_MODEL_SPACE, pBlockTableRecord,
AcDb::kForWrite);
pBlkTable2->close();

AcDbObjectId lineId=AcDbObjectId::kNull;
pBlockTableRecord->appendAcDbEntity(lineId, pLine);
pBlockTableRecord->close();
pLine->close();
return (1) ;
}
}

void changepoint(ads_point& ads_pt,AcGePoint3d acge_pt) //AcGePoint3d转换成ads_point类型
{
double x=acge_pt[0];
double y=acge_pt[1];
double z=acge_pt[2];
ads_pt[X]=x;
ads_pt[Y]=y;
ads_pt[Z]=z;
}

c735023723

把多边形变成N个三角形，然后用海伦公式计算就可以了