for(i=0;i<=MaxY;i++)
{
pNET[i]=new NET;
pNET[i]->next=NULL;
}
/扫描并建立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);
