计算机图形学实验报告实验2裁剪算法实验

一、 实验目的：

直线段的裁剪：编码裁剪算法，中点分割裁剪算法。

二、实验内容：

//BasicGraph.cpp

//请将下列裁剪程序补充完整，并用注释说明是何种裁剪算法

void Encode (int x,int y,int *code,int XL,int XR,int YB,int YT) {

//请将此程序补充完整 int c=0;

if(x

else if(x>XR) c=c|RIGHT; if(yYT) c=c|TOP; (*code)=c; }

//编码裁剪算法：

void C_S_Line(POINT &p1,POINT &p2,int XL,int XR,int YB,int YT) {

//请将此程序补充完整

int x1,x2,y1,y2,x,y,code1,code2,code; x1=p1.x; x2=p2.x; y1=p1.y; y2=p2.y; Encode(x1,y1,&code1,XL,XR,YB,YT); Encode(x2,y2,&code2,XL,XR,YB,YT); while(code1!=0||code2!=0) {

if((code1&code2)!=0) return; code=code1;

if(code1==0) code=code2; if((LEFT&code)!=0)

{x=XL;y=y1+(y2-y1)*(XL-x1)/(x2-x1);} else if((RIGHT&code)!=0)

{x=XR;y=y1+(y2-y1)*(XR-x1)/(x2-x1);} if((BOTTOM&code)!=0)

{y=YB;x=x1+(x2-x1)*(YB-y1)/(y2-y1);} else if((TOP&code)!=0)

{y=YT;x=x1+(x2-x1)*(YT-y1)/(y2-y1);} if(code==code1)

{x1=x;y1=y;Encode(x,y,&code1,XL,XR,YB,YT);} else

{x2=x;y2=y;Encode(x,y,&code2,XL,XR,YB,YT);} }

p1.x=x1;p1.y=y1;p2.x=x2;p2.y=y2; }

int IsInArea(POINT point,int XL,int XR,int YB,int YT) {

//请将此程序补充完整

if(point.x>=XL && point.x<=XR && point.y>YB && point.y

else return 0; }

int NotIntersect(POINT begin,POINT end,int XL,int XR,int YB,int YT) {

//请将此程序补充完整

int maxx,maxy,minx,miny;

maxx=(begin.x>end.x)?begin.x:end.x; minx=(begin.xend.y)?begin.y:end.y; miny=(begin.y

if(maxxXR||maxyYT) return 1; else return 0; }

//中点裁剪算法：

POINT ClipMid(POINT begin,POINT end,int XL,int XR,int YB,int YT) {

//请将此程序补充完整 POINT mid,temp;

if(IsInArea(begin,XL,XR,YB,YT)) temp=begin;

else if(NotIntersect(begin,end,XL,XR,YB,YT)) temp=begin; else {

mid.x=(begin.x+end.x)/2;mid.y=(begin.y+end.y)/2;

if(abs(mid.x-end.x)<=1&& abs(mid.y-end.y)<=1) temp=mid; else {

if(NotIntersect(begin,mid,XL,XR,YB,YT)) temp=ClipMid(mid,end,XL,XR,YB,YT); else

temp=ClipMid(begin,mid,XL,XR,YB,YT); } }

return temp; }

//Liang-Barsky直线裁剪算法：

void ClipParameter(POINT &p1,POINT &p2,int XL,int XR,int YB,int YT) {

float u1=0.0,u2=1.0;

float dx=p2.x-p1.x,dy=p2.y-p1.y; if(clipTest(-dx,p1.x-XL,&u1,&u2)) if(clipTest(dx,XR-p1.x,&u1,&u2)) if(clipTest(-dy,p1.y-YB,&u1,&u2)) if(clipTest(dy,YT-p1.y,&u1,&u2)) {

if(u2<1.0) {

p2.x=p1.x+u2*dx; p2.y=p1.y+u2*dy; }

if(u1>0.0) {

p1.x=p1.x+u1*dx; p1.y=p1.y+u1*dy; } } }

int clipTest(float p,float q,float *u1,float *u2) {

float r;

int remainFlag=1; if(p<0.0) {

r=q/p;

if(r>*u2) remainFlag=0; else if(r>*u1) *u1=r; }

else if(p>0.0) {

r=q/p;

if(r<*u1) remainFlag=0; else if(r<*u2) *u2=r; }

else //*p=0

if(q<0.0) remainFlag=0;

return remainFlag; }

//逐边裁剪算法：

//typedef struct tRes { int yes,isIn; POINT pout;} Res; Res TestIntersect(int edge,int type,POINT p1,POINT p2)

{//判断p2是否在所裁剪的窗边edge的内侧，是否与p1点分别在窗边edge的异侧

float dx,dy,m;

Res res;int isIn=0,yes=0;POINT pout; dy=p2.y-p1.y;dx=p2.x-p1.x;m=dy/dx; switch(type) {

case 1: /*right*/

if(p2.x<=edge){isIn=1;if(p1.x>edge)yes=1;} else if(p1.x<=edge)yes=1;break; case 2: /*bottom*/

if(p2.y>=edge){isIn=1;if(p1.y=edge)yes=1;break; case 3: /*left*/

if(p2.x>=edge){isIn=1;if(p1.x=edge)yes=1;break; case 4: /*top*/

if(p2.y<=edge){isIn=1;if(p1.y>edge)yes=1;} else if(p1.y<=edge)yes=1; default: break; }

if(yes) {

if((type==1) || (type==3))

{ pout.x=edge;pout.y=p1.y+m*(pout.x-p1.x);} if((type==2) || (type==4))

{ pout.y=edge;pout.x=p1.x+(pout.y-p1.y)/m;} }

res.isIn=isIn;res.yes=yes;res.pout=pout; return res; }

int clipSingleEdge(int edge,int type,int nin,POINT pin[50],POINT pout[50])

/*对多边形pin与窗边edge进行裁剪，返回裁剪后的多边形pout及点数*/ {

int i,k=0;POINT p;Res res;

p.x=pin[nin-1].x;p.y=pin[nin-1].y;

for(i=0;i

res=TestIntersect(edge,type,p,pin[i]); if(res.yes)

{ pout[k].x=res.pout.x;pout[k].y=res.pout.y;k++;} if(res.isIn)

{ pout[k].x=pin[i].x;pout[k].y=pin[i].y;k++;} p.x=pin[i].x;p.y=pin[i].y; }

return k; }

void ClipEdgePolygon(POINT ps[50],int &n,int XL,int XR,int YB,int YT) { /*对多边形ps进行逐边裁剪*/ int n1=0,n2=0; POINT pt[50];

n1=clipSingleEdge(XR,1,n,ps,pt); n2=clipSingleEdge(YB,2,n1,pt,ps); n1=clipSingleEdge(XL,3,n2,ps,pt); n2=clipSingleEdge(YT,4,n1,pt,ps); n=n2; }

//多边形编码裁剪算法：

void ClipEncodePolygon(POINT ps[50],int &n,int XL,int XR,int YB,int YT) {

POINT tp[50]; int k=0,m;

int code1,code2,code; int x,y;

for(int i=0;i

Encode(ps[i].x,ps[i].y,&code1,XL,XR,YB,YT);

Encode(ps[i+1].x,ps[i+1].y,&code2,XL,XR,YB,YT); code=code1;m=i;

for(int j=0;j<2;j++) {

if((code1 & code2)!=0) //线段两端都在窗口外的同一侧 {

switch(code) {

case 1:x=XL;y=ps[m].y;break; case 2:x=XR;y=ps[m].y;break; case 4:x=ps[m].x;y=YB;break; case 5:x=XL;y=YB;break; case 6:x=XR;y=YB;break;