图形学算法设计和流程图ppt课件.ppt

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1、DDA算法设计,A、数据结构设计函数定义：DDA算法函数：void CTestView:DDALine(int xa,int ya,int xb,int yb)方法调用函数：void CTestView :OnDDALineFunc1()鼠标响应函数：void CTestView :OnDDALineMouse1()鼠标按下事件：void CTestView :OnLButtonDown(UINT nFlags, CPoint point) 鼠标抬起事件：void CTestView :OnLButtonUp(UINT nFlags, CPoint point)B、核心算法设计DDA算法：设直

2、线起点（x0,y0），终点(x1,y1)，k为直线斜率，因有直线公式为y=kx+b，则有斜率k=（y1-y0）/(x1-x0)；当|k|=1时，y坐标：yi+1=yi+1，x坐标：xi+1=xi+1/k；当|k|1时，y坐标：yi+1=yi+k，x坐标：xi+1=xi+1。,DDA算法（1）输入,DDA算法（2）处理,DDA算法（3）输出,DDA算法,void CTestView:OnDDALineFunc1()/调用DDALine函数CTestView:DDALine(50,50,150,200);/起点（50,50），终点（150,200）void CTestView:OnDDALineM

3、ouse1() /鼠标响应调用DDALine函数flag=5;void CTestView:OnLButtonDown(UINT nFlags, CPoint point) /鼠标按下事件bx=point.x; /获取鼠标按下时的横坐标by=point.y; /获取鼠标按下时的横坐标CView:OnLButtonDown(nFlags, point);void CTestView:OnLButtonUp(UINT nFlags, CPoint point)/鼠标抬起事件CClientDC dc(this);if(flag=5)CTestView:DDALine(bx,by,point.x,po

4、int.y); /鼠标响应调用DDALine函数CView:OnLButtonUp(nFlags, point);,DDA算法,void CTestView:DDALine(int xa,int ya,int xb,int yb) /DDALine函数算法CClientDC dc(this);float x,y,k,dx,dy,temp;if(xa=xb)/当xa=xb时，k=0，直线垂直于y轴for(y=ya;y=yb;y+)dc.SetPixel(xa,y,RGB(255,0,0);else/当xa!=xb时，计算斜率k，判断绝对值值域dx=(float)(xb-xa);dy=(float

5、)(yb-ya);k=dy/dx;/求斜率,DDA算法,if(xaxb) if(xaxb)/确保直线从左向右画temp=xa;xa=xb;xb=temp;temp=ya;ya=yb;yb=temp;y=ya;for(x=xa;x=1)/判断k的绝对值，|k|=1时执行if(yayb)/确保直线从左向右画temp=xa;xa=xb;xb=temp;temp=ya;ya=yb;yb=temp;x=xa;for(y=ya;y=yb;y+)/循环yi+1=yi+1dc.SetPixel(int)(x+0.5),y,RGB(255,0,0);/画点x=x+1/k; ,中点画圆算法,A.数据结构设计：函数

6、定义：中点画圆算法函数：void CTestView:midpointcircle(int xa,int ya,int xb,int yb)鼠标按下事件：void CTestView :OnLButtonDown(UINT nFlags, CPoint point) 鼠标抬起事件：void CTestView :OnLButtonUp(UINT nFlags, CPoint point)圆心在原点中点画圆事件：void CTestView :Onzero1()圆心在任意点中点画圆事件：void CTestView :Onanypoint1()B.中点画圆算法设计： 函数为F(x,y)=x2+y

7、2-r2的构造圆，半径r等于鼠标响应事件得到的亮点坐标的距离，即r=sqrt(xb-xa)*(xb-xa)+(yb-ya)*(yb-ya)。 设d=F(x,y)，判断d的符号，d=0的M点在圆上，d0的M点在圆外，d=0时，d更新为d+2x+3，(x,y)更新为(x+1,y)；当d0时，d更新为d+2*(x-y)+5，(x,y)更新为(x+1,y+1)。 当xy时，重复计算绘制点。,中点画圆算法-流程图,中点画圆算法-1,void CTestView :midpointcircle(int xa,int ya,int xb,int yb)CClientDC dc(this);int fzbj=

8、(xb-xa)*(xb-xa)+(yb-ya)*(yb-ya);int r=int(sqrt(double)fzbj),c=0;int x,y;float d;x=0;y=r;d=1.25-r;dc.SetPixel(xa+x,ya+y,c);dc.SetPixel(xa-x,ya+y,c);dc.SetPixel(xa+x,ya-y,c);dc.SetPixel(xa-x,ya-y,c);dc.SetPixel(xa+y,ya+x,c);dc.SetPixel(xa-y,ya+x,c);dc.SetPixel(xa+y,ya-x,c);dc.SetPixel(xa-y,ya+x,c);,中点

9、画圆算法-2,while(x=y)if(d0) d+=2*x+3;else d+=2*(x-y)+5;y-;x+;dc.SetPixel(xa+x,ya+y,c);dc.SetPixel(xa-x,ya+y,c);dc.SetPixel(xa+x,ya-y,c);dc.SetPixel(xa-x,ya-y,c);dc.SetPixel(xa+y,ya+x,c);dc.SetPixel(xa-y,ya+x,c);dc.SetPixel(xa+y,ya-x,c);dc.SetPixel(xa-y,ya-x,c);void CTestView :Onzero1()flag=6;void CTestV

10、iew :Onanypoint1()flag=7;,中点画圆算法-3,void CTestView :OnLButtonDown(UINT nFlags, CPoint point)bx=point.x;by=point.y;CView:OnLButtonDown(nFlags, point);void CTestView :OnLButtonUp(UINT nFlags, CPoint point)CClientDC dc(this);else if(flag=6) CTestView :midpointcircle(0,0,point.x,point.y);else if(flag=7)

11、CTestView :midpointcircle(bx,by,point.x,point.y);CView:OnLButtonUp(nFlags, point);,二维图形裁剪-线段裁剪,计算点的code值流程图,二维图形裁剪-线段裁剪,计算直线与边界交点流程图,二维图形裁剪-线段裁剪,算法流程图1,二维图形裁剪-线段裁剪,算法流程图2,二维图形裁剪-线段裁剪,算法流程图总,二维图形裁剪-1,void CTestView :OnCohenSutherland1() flag=8;CClientDC dc(this);/边框dc.MoveTo(200,100); /LEFTdc.LineTo(

12、200,400);dc.MoveTo(500,100); /RIGHTdc.LineTo(500,400);dc.MoveTo(200,100);/TOPdc.LineTo(500,100);dc.MoveTo(200,400); /BOTTONdc.LineTo(500,400);void CTestView :OnLButtonDown(UINT nFlags, CPoint point) bx=point.x;by=point.y;CView:OnLButtonDown(nFlags, point);,二维图形裁剪-1,void CTestView :OnLButtonUp(UINT n

13、Flags, CPoint point) CClientDC dc(this);if(flag=8)dc.MoveTo(bx,by);dc.LineTo(point.x,point.y);ClipLine(bx,by,point.x,point.y);CView:OnLButtonUp(nFlags, point); int CTestView :encode(float x,float y)int c;c=0;if(xXR)c=c|RIGHT;if(yYB)c=c|BOTTOM;else if(yYT)c=c|TOP;return c;,二维图形裁剪-2,void CTestView :Cl

14、ipLine(float x1,float y1,float x2,float y2)CClientDC dc(this);float x,y;int code,code1,code2;code1=encode(x1,y1);code2=encode(x2,y2);while(code1!=0 |code2!=0) if(code1,二维图形裁剪-3,/当直线和左边界有交点if(LEFT,二维图形裁剪-4,if(code=code1)x1=x;y1=y;code1 =encode(x,y); elsex2=x;y2=y;code2 =encode(x,y);CPen pen,*old;pen.CreatePen(0,2,RGB(255,0,0);old=dc.SelectObject(,