图形学三维线段的裁剪显示.doc

三维线段的裁剪及显示专 业：信计0902小组成员：王文祥、高天宇、何弯弯、崔文强、王豹时 间：2011年12月28日课程设计题目： 三维线段的裁剪及显示题目要求： 对于三维线段，裁剪体为长方体，应用端点编码或Liang-Barsky裁剪算法对线段进行裁剪，做XOY平面的平行投影，要求分别绘制裁剪体、带裁剪线段和裁剪后线段。任务分析：（1）长方体及三维线段的显示流程 ；任务包括长方体的定义：三维点结构（齐次坐标，结构中应有x, y, z, w分量）；面结构，其实为面的外环，即构成该面的顶点序列（逆时针顺序）；三维线段的两个端点；三维几何变换；平行投影变换；窗口-视区变换；（2）三维线段的端点编码或Liang-Barsky裁剪算法；任务长方体的六个边界定义，三维点的端点编码，三维线段端点编码裁剪算法；核心算法描述：Liang _Barsky裁剪算法基本思想： 更快的直线裁剪算法基于线段的参数化方程的分析，可以把直线方程写成以下形式： 其中，若点满足：则该点在窗口内。首先按参数化形式写出该形式的裁剪条件： 这四个不等式可以表示为： 其中，参数p,q定义为：若，其中，k对应于该裁剪边界（k=0,1,2,3,4,5,6对应于左、右、下、上边界）若，则线段完全在边界外；若，则线段平行于该裁剪边界并且在窗口内；当，线段从裁剪边界延长线的外部延伸到内部；当，线段从裁剪边界的内部延伸到外部；算法步骤 定义结构和变量 定义三维齐次坐标结构和面结构；定义长方体表面模型，顶点表为顶点结构数组pts8，面表为面结构数组faces6；定义待裁剪线段的两个端点p1，p2和裁剪后线段的两个端点p3，p4。 变量初始化 在视图类构造函数中给顶点表赋值；给面表赋值（注意顶点序列顺序）；给待裁剪线段端点赋值；给待裁剪线段端点赋原点值进行初始化。 在视图类中添加计算端点编码的函数；添加三维线段裁决的函数。定义线段裁剪时用到的六条边界，各边界的取值为长方体相应的值。 分别对长方体、待裁剪线段、裁剪后线段进行绕X轴旋转，再绕Y轴旋转。 分别对长方体、待裁剪线段、裁剪后线段进行以XOY平面为投影平面的平行投影变换。 分别对长方体、待裁剪线段、裁剪后线段进行窗口视区变换，注意窗口的选区。 显示变换后长方体，用实线绘制待裁剪线段，定义画笔，用虚线绘制裁剪后线段。 程序核心代码：视图类头文件/ Draw3DView.h : interface of the CDraw3DView class/#if !defined(AFX_DRAW3DVIEW_H_49195EF8_8785_46EA_89D5_35CD8D2F85C7_INCLUDED_)#define AFX_DRAW3DVIEW_H_49195EF8_8785_46EA_89D5_35CD8D2F85C7_INCLUDED_#if _MSC_VER 1000#pragma once#endif / _MSC_VER 1000#define PI 3.1415926/定义三维齐次坐标结构typedef struct tagHOMOCOORDfloat x;float y;float z;float w;HOMOCOORD;/定义边的结构typedef struct tagLINEint p1,p2;LINE;/定义面的结构typedef struct tagPLANEint v0, v1, v2, v3;bool isvisible;PLANE;/定义点的结构，需要浮点数的x，ytypedef struct tagMYPOINTfloat x,y;MYPOINT;class CDraw3DView : public CViewprotected: / create from serialization onlyCDraw3DView();DECLARE_DYNCREATE(CDraw3DView)/ Attributespublic:CDraw3DDoc* GetDocument();/ Operationspublic:/ Overrides/ ClassWizard generated virtual function overrides/AFX_VIRTUAL(CDraw3DView)public:virtual void OnDraw(CDC* pDC); / overridden to draw this viewvirtual BOOL PreCreateWindow(CREATESTRUCT& cs);protected:virtual BOOL OnPreparePrinting(CPrintInfo* pInfo);virtual void OnBeginPrinting(CDC* pDC, CPrintInfo* pInfo);virtual void OnEndPrinting(CDC* pDC, CPrintInfo* pInfo);/AFX_VIRTUAL/ Implementationpublic:int CT(float p,float q,float *u1,float *u2);void LB(HOMOCOORD p1,HOMOCOORD p2,int xl,int xr,int yb,int yt,int zf,int zb);HOMOCOORD GetN(HOMOCOORD p1,HOMOCOORD p2,HOMOCOORD p3);void RotateY(int angle);void RotateX(int angle);void DrawMy3DGraphics();virtual CDraw3DView();#ifdef _DEBUGvirtual void AssertValid() const;virtual void Dump(CDumpContext& dc) const;#endifprotected:HOMOCOORD *pts,*p,*pp;MYPOINT *pts2D,*p2D,*pp2D;PLANE *faces;int ptn,fn;/ Generated message map functionsprotected:/AFX_MSG(CDraw3DView)/ NOTE - the ClassWizard will add and remove member functions here./ DO NOT EDIT what you see in these blocks of generated code !/AFX_MSGDECLARE_MESSAGE_MAP();#ifndef _DEBUG / debug version in Draw3DView.cppinline CDraw3DDoc* CDraw3DView:GetDocument() return (CDraw3DDoc*)m_pDocument; #endif/AFX_INSERT_LOCATION/ Microsoft Visual C+ will insert additional declarations immediately before the previous line.#endif / !defined(AFX_DRAW3DVIEW_H_49195EF8_8785_46EA_89D5_35CD8D2F85C7_INCLUDED_)视图类源文件/ Draw3DView.cpp : implementation of the CDraw3DView class/#include stdafx.h#include Draw3D.h#includemath.h#include Draw3DDoc.h#include Draw3DView.h#ifdef _DEBUG#define new DEBUG_NEW#undef THIS_FILEstatic char THIS_FILE = _FILE_;#endif/ CDraw3DViewIMPLEMENT_DYNCREATE(CDraw3DView, CView)BEGIN_MESSAGE_MAP(CDraw3DView, CView)/AFX_MSG_MAP(CDraw3DView)/ NOTE - the ClassWizard will add and remove mapping macros here./ DO NOT EDIT what you see in these blocks of generated code!/AFX_MSG_MAP/ Standard printing commandsON_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()/ CDraw3DView construction/destructionCDraw3DView:CDraw3DView()/ TODO: add construction code hereCDraw3DView:CDraw3DView()BOOL CDraw3DView:PreCreateWindow(CREATESTRUCT& cs)/ TODO: Modify the Window class or styles here by modifying/ the CREATESTRUCT csreturn CView:PreCreateWindow(cs);/ CDraw3DView drawingvoid CDraw3DView:OnDraw(CDC* pDC)CDraw3DDoc* pDoc = GetDocument();ASSERT_VALID(pDoc);/ TODO: add draw code for native data hereDrawMy3DGraphics();/ CDraw3DView printingBOOL CDraw3DView:OnPreparePrinting(CPrintInfo* pInfo)/ default preparationreturn DoPreparePrinting(pInfo);void CDraw3DView:OnBeginPrinting(CDC* /*pDC*/, CPrintInfo* /*pInfo*/)/ TODO: add extra initialization before printingvoid CDraw3DView:OnEndPrinting(CDC* /*pDC*/, CPrintInfo* /*pInfo*/)/ TODO: add cleanup after printing/ CDraw3DView diagnostics#ifdef _DEBUGvoid CDraw3DView:AssertValid() constCView:AssertValid();void CDraw3DView:Dump(CDumpContext& dc) constCView:Dump(dc);CDraw3DDoc* CDraw3DView:GetDocument() / non-debug version is inlineASSERT(m_pDocument-IsKindOf(RUNTIME_CLASS(CDraw3DDoc);return (CDraw3DDoc*)m_pDocument;#endif /_DEBUG/ CDraw3DView message handlersvoid CDraw3DView:DrawMy3DGraphics()p=new HOMOCOORD4;p0.x=2; p0.y=-3; p0.z=2; p0.w=1;p1.x=-2; p1.y=3; p1.z=-2; p1.w=1;p2.x=2; p2.y=-3; p2.z=2; p2.w=1;p3.x=-2; p3.y=3; p3.z=-2; p3.w=1;/形体定义ptn=8;pts=new HOMOCOORDptn;/设置长方体pts0.x=1; pts0.y=2; pts0.z=1; pts0.w=1;pts1.x=-1; pts1.y=2; pts1.z=1; pts1.w=1;pts2.x=-1; pts2.y=-2; pts2.z=1; pts2.w=1;pts3.x=1; pts3.y=-2; pts3.z=1; pts3.w=1;pts4.x=1; pts4.y=2; pts4.z=-1; pts4.w=1;pts5.x=-1; pts5.y=2; pts5.z=-1; pts5.w=1;pts6.x=-1; pts6.y=-2; pts6.z=-1; pts6.w=1;pts7.x=1; pts7.y=-2; pts7.z=-1; pts7.w=1;/给定义面的指针分配内存；fn=6;faces=new PLANEfn;/设置立方体各面faces0.v0=0; faces0.v1=1; faces0.v2=2; faces0.v3=3; faces0.isvisible =false;faces1.v0=4; faces1.v1=5; faces1.v2=1; faces1.v3=0; faces1.isvisible =false;faces2.v0=5; faces2.v1=6; faces2.v2=2; faces2.v3=1; faces2.isvisible =false;faces3.v0=6; faces3.v1=7; faces3.v2=3; faces3.v3=2; faces3.isvisible =false;faces4.v0=7; faces4.v1=4; faces4.v2=0; faces4.v3=3; faces4.isvisible =false;faces5.v0=7; faces5.v1=6; faces5.v2=5; faces5.v3=4; faces5.isvisible =false;pts2D=new MYPOINTptn;p2D=new MYPOINT2;int i;LB(p0,p1,-1,1,-2,2,1,-1); RotateX(20); RotateY(30);HOMOCOORD view; /视线方向view.x=0; view.y=0; view.z=1;view.w=1;for(i=0;i0)facesi.isvisible=true;/平行投影变换for(i=0;iptn;i+)pts2Di.x=ptsi.x;pts2Di.y=ptsi.y;for(i=0;i4;i+)p2Di.x=pi.x;p2Di.y=pi.y;/窗口-视区变换实现过程float wxl=-3,wxr=3,wyb=-3,wyt=3;int vxl=0,vxr=500,vyb=0,vyt=400;float sx=(vxr-vxl)/(wxr-wxl),sy=(vyt-vyb)/(wyt-wyb),dx=vxl-sx*wxl,dy=vyb-sy*wyb;for(i=0;iptn;i+)pts2Di.x=sx*pts2Di.x+dx;pts2Di.y=sy*pts2Di.y+dy;for(i=0;i4;i+)p2Di.x=sx*p2Di.x+dx;p2Di.y=sy*p2Di.y+dy;/图形显示CClientDC dc(this);dc.MoveTo (p2D0.x,p2D0.y);/实线dc.LineTo (p2D1.x,p2D1.y);CPen *pOld,newpen(PS_DOT,1,RGB(0,0,0);pOld=dc.SelectObject(&newpen); dc.MoveTo (p2D2.x,p2D2.y);dc.LineTo (p2D3.x,p2D3.y);for( i=0;ifn;i+) /显示每个面上的各边 /设置画笔为虚线PLANE f=facesi;if(!f.isvisible ) /如果该面为不可见面dc.MoveTo (pts2Df.v0 .x,pts2Df.v0.y);dc.LineTo (pts2Df.v1.x,pts2Df.v1.y);dc.LineTo (pts2Df.v2.x,pts2Df.v2.y);dc.LineTo (pts2Df.v3.x,pts2Df.v3.y);dc.LineTo (pts2Df.v0.x,pts2Df.v0.y);dc.SelectObject(pOld); /把画笔设置为原理的实线for( i=0;ifn;i+) /显示每个面上的各边PLANE f=facesi;if(f.isvisible ) /如果该面为不可见面dc.MoveTo (pts2Df.v0 .x,pts2Df.v0.y);dc.LineTo (pts2Df.v1.x,pts2Df.v1.y);dc.LineTo (pts2Df.v2.x,pts2Df.v2.y);dc.LineTo (pts2Df.v3.x,pts2Df.v3.y);dc.LineTo (pts2Df.v0.x,pts2Df.v0.y);void CDraw3DView:RotateX(int angle)float a=angle*PI/180;for(int i=0;iptn;i+)float x,y,z;y=ptsi.y;z=ptsi.z;x=ptsi.x;ptsi.y=y*cos(a)-z*sin(a);ptsi.z=y*sin(a)+z*cos(a);for(i=0;i4;i+)float x,y,z;y=pi.y;z=pi.z;x=pi.x;pi.y=y*cos(a)-z*sin(a);pi.z=y*sin(a)+z*cos(a);void CDraw3DView:RotateY(int angle)float b=angle*PI/180;for(int i=0;iptn;i+)float x,y,z;x=ptsi.x;z=ptsi.z;y=ptsi.y;ptsi.x=x*cos(b)-z*sin(b);ptsi.z=x*sin(b)+z*cos(b);for(i=0;i4;i+)float x,y,z;x=pi.x;z=pi.z;y=pi.y;pi.x=x*cos(b)-z*sin(b);pi.z=x*sin(b)+z*cos(b);HOMOCOORD CDraw3DView:GetN(HOMOCOORD p1, HOMOCOORD p2, HOMOCOORD p3) float x1=p2.x-p1.x, y1=p2.y-p1.y,z1=p2.z-p1.z;float x2=p3.x-p2.x, y2=p3.y-p2.y, z2=p3.z-p2.z;HOMOCOORD N;N.x=y1*z2-y2*z1; N.y=-(x1*z2-x2*z1); N.z=x1*y2-x2*y1;return N;void CDraw3DView:LB(HOMOCOORD p1, HOMOCOORD p2, int xl, int xr, int yb