C++多边形扫描转换算法

　　近期学习计算机图形学,写了个多边形扫描转换算法,贴出来分享一下;

　　MFC还不是太清楚,重要还是 使用OnDraw函数...

　　大家多指教...

void CPolyFillView::OnDraw(CDC* pDC)

{

CPolyFillDoc* pDoc = GetDocument();

ASSERT_VALID(pDoc);

// TODO: add draw code for native data here

const int POINTNUM=6; //多边形点数.

/定义 构造体用于活性边表AET和新边表NET/

typedef struct XET

{

float x;

float dx,ymax;

XET* next;

}AET,NET;

/定义点 构造体point*/

struct point

{

float x;

float y;

}polypoint[POINTNUM]={250,50,550,150,550,400,250,250,100,350,100,100};//多边形顶点

//mypoint[POINTNUM]={100,100,200,100,200,200,100,200};//正方形

/计算最高点的y坐标(扫描到此 完毕)**/

int MaxY=0;

int i;

for(i=0;i<POINTNUM;i++)

if(polypoint[i].y>MaxY)

MaxY=polypoint[i].y;

/*初始化AET表/

AET *pAET=new AET;

pAET->next=NULL;

/初始化NET表*/

NET *pNET[1024];

for(i=0;i<=MaxY;i++)

{

pNET[i]=new NET;

pNET[i]->next=NULL;

}

/扫描并 构建NET表*/

for(i=0;i<=MaxY;i++)

{

for(int j=0;j<POINTNUM;j++)

if(polypoint[j].y==i)

{

if(polypoint[(j-1+POINTNUM)%POINTNUM].y>polypoint[j].y)

{

NET *p=new NET;

p->x=polypoint[j].x;

p->ymax=polypoint[(j-1+POINTNUM)%POINTNUM].y;

p->dx=(polypoint[(j-1+POINTNUM)%POINTNUM].x-polypoint[j].x)/(polypoint[(j-1+POINTNUM)%POINTNUM].y-polypoint[j].y);

p->next=pNET[i]->next;

pNET[i]->next=p;

}

if(polypoint[(j+1+POINTNUM)%POINTNUM].y>polypoint[j].y)

{

NET *p=new NET;

p->x=polypoint[j].x;

p->ymax=polypoint[(j+1+POINTNUM)%POINTNUM].y;

p->dx=(polypoint[(j+1+POINTNUM)%POINTNUM].x-polypoint[j].x)/(polypoint[(j+1+POINTNUM)%POINTNUM].y-polypoint[j].y);

p->next=pNET[i]->next;

pNET[i]->next=p;

}

}

}

/ 构建并更新活性边表AET/

for(i=0;i<=MaxY;i++)

{

//计算新的交点x,更新AET/

NET *p=pAET->next;

while(p)

{

p->x=p->x + p->dx;

p=p->next;

}

//更新后新AET先排序