绘制多边形时用桶结构,其实类似于图里面的邻接表,从上到下是桶(bucket),右边链接的指针是边(edge).
class Bucket //桶类
{
public:
Bucket();
virtual ~Bucket();
int ScanLine;
AET *p;//桶上的边表指针
Bucket *next;
};
class Edge //边类
{
public:
Edge();
virtual ~Edge();
double x;
int yMax;
double k;//代替1/k
Edge *next;
};
边链表E[]中保存的是: yMax表示一条线段的下面点的Y值,x表示上面点的X值(扫描下一条线时会加 1/k, 其中k为斜率)
绘制扫描线时,有时扫描线被分为几段,但每次都是取二个点并绘制(如Y0中的L1,L2)如下图所示:
源代码如下:
// TestView.cpp : implementation of the CTestView class
//
#include "stdafx.h"
#include "Test.h"
#include "TestDoc.h"
#include "TestView.h"
#ifdef _DEBUG
#define new DEBUG_NEW
#undef THIS_FILE
static char THIS_FILE[] = __FILE__;
#endif
#define ROUND(a) int(a+0.5)//四舍五入
/
// CTestView
IMPLEMENT_DYNCREATE(CTestView, CView)
BEGIN_MESSAGE_MAP(CTestView, CView)
//{{AFX_MSG_MAP(CTestView)
ON_COMMAND(ID_MENUAET, OnMenuAET)
//}}AFX_MSG_MAP
// Standard printing commands
ON_COMMAND(ID_FILE_PRINT, CView::OnFilePrint)
ON_COMMAND(ID_FILE_PRINT_DIRECT, CView::OnFilePrint)
ON_COMMAND(ID_FILE_PRINT_PREVIEW, CView::OnFilePrintPreview)
END_MESSAGE_MAP()
/
// CTestView construction/destruction
CTestView::CTestView()
{
// TODO: add construction code here
//设置多边形的7个顶点
Point[0]=CPoint(550,400);//P0
Point[1]=CPoint(350,600);//P1
Point[2]=CPoint(250,350);//P2
Point[3]=CPoint(350,50);//P3
Point[4]=CPoint(500,250);//P4
Point[5]=CPoint(600,50);//P5
Point[6]=CPoint(800,450);//P6
}
CTestView::~CTestView()
{
}
BOOL CTestView::PreCreateWindow(CREATESTRUCT& cs)
{
// TODO: Modify the Window class or styles here by modifying
// the CREATESTRUCT cs
return CView::PreCreateWindow(cs);
}
/
// CTestView drawing
void CTestView::OnDraw(CDC* pDC)
{
CTestDoc* pDoc = GetDocument();
ASSERT_VALID(pDoc);