计算机图形学实验（三）梁友栋-Barskey线段裁剪和多边形裁剪算法实现

- 日理万妓 2022-02-04 13:23 377阅读 0赞

# 梁友栋-Barskey裁剪算法 #

直接上代码吧：

// ConsoleApplication2.cpp: 定义控制台应用程序的入口点。
    //
    #include "stdafx.h"
    #include<gl/GLUT.H>
    #include<cmath>
    #include<iostream>
    #include"node.h"
    using namespace std;
    void Initial(void)//初始化函数 
    { 
    	glClearColor(1.0f, 1.0f, 1.0f, 1.0f);//白色背景，前3个是RGB，最后是Alpha值，用来控制透明，1.0表示完全不透明
    	glMatrixMode(GL_MODELVIEW);//OpenGL按照三维方式来处理图像，所以需要一个投影变换将三维图形投影到显示器的二维空间中
    	glLoadIdentity();
    	gluOrtho2D(0.0, 400, 0.0, 400.0);//指定使用正投影将一个x坐标在0~200，y坐标0~150范围内的矩形坐标区域投影到显示器窗口
    
    }
    bool ClipT(float p, float q, float *u1, float *u2)
    { 
    	float r;
    	if (p < 0)
    	{ 
    		r = q / p;
    		
    		if (r > *u2)
    			return false;
    		if (r > *u1)
    			* u1 = r;
    	}
    	else if (p > 0)
    	{ 
    		r = q / p;
    		if (r < *u1)
    			return false;
    		if (r < *u2)
    			*u2 = r;
    	}
    	else
    		return (q >= 0);
    	return true;
    }
    void LB_LineClip(float x1, float y1, float x2, float y2, float XL, float XR, float YB, float YT)
    { 
    	float dx, dy, u1, u2;
    	 u1 = 0, u2 = 1;
    	dx = x2 - x1;
    	dy = y2 - y1;
    	glClearColor(0.0f, 0.0f, 0.0f, 0.0f);//绘图颜色为黑色 
    	glClear(GL_COLOR_BUFFER_BIT);
    	glColor3f(1.0, 0.0, 0.0);
    	glViewport(0, 0, 400, 400);
    	glBegin(GL_LINES);
    	glVertex2f(x1, y1);
    	glVertex2f(x2, y2);
    	glEnd();
    	//glClearColor(0.0f, 0.0f, 0.0f, 0.0f);//绘图颜色为黑色 
    	//glClear(GL_COLOR_BUFFER_BIT);
    	glColor3f(1.0, 1.0, 1.0);
    	glViewport(0, 0, 400, 400);
    	glBegin(GL_LINES);
    	glVertex2f(XL,YB);
    	glVertex2f(XL,YT);
    	glVertex2f(XL,YT);
    	glVertex2f(XR,YT);
    	glVertex2f(XR, YT);
    	glVertex2f(XR, YB);
    	glVertex2f(XL, YB);
    	glVertex2f(XR, YB);
    	if (ClipT(-dx, x1 - XL, &u1, &u2))
    		if (ClipT(dx, XR - x1, &u1, &u2))
    			if (ClipT(-dy, y1 - YB, &u1, &u2))
    				if (ClipT(dy, YT - y1, &u1, &u2))
    				{ 
    
    					glVertex2f(x1 + u1 * dx, y1 + u1 * dy);
    					glVertex2f(x1 + u2 * dx, y1 + u2 * dy);
    					
    
    				}
    	glEnd();
    	glFlush();
    }
    node* Sutherland(node *m1, node *m2, side ClipBoundary, int Inlength, int &Outlength)
    { 
    	node S, P, ip;
    	int j;
    	Outlength = 0;
    	S = m1[Inlength - 1];
    	for (j = 0; j < Inlength; j++)
    	{ 
    		P = m1[j];
    		if (Inside(P, ClipBoundary))
    		{ 
    			if (Inside(S, ClipBoundary))
    				Output(P, Outlength, m2);
    			else
    			{ 
    				Intersect(S, P, ClipBoundary, ip);
    				Output(ip, Outlength, m2);
    				Output(P, Outlength, m2);
    			}
    		}
    		else if (Inside(S, ClipBoundary))
    		{ 
    			Intersect(S, P, ClipBoundary, ip);
    			Output(ip, Outlength, m2);
    		}
    		S = P;
    	}
    
    	return m2;
    }
    void drawFront(node m1[],node m2[],int length1,int length2)
    { 
    	glClearColor(0.0f, 0.0f, 0.0f, 0.0f);//绘图颜色为黑色 
    	glClear(GL_COLOR_BUFFER_BIT);
    	glColor3f(1.0, 1.0, 0.0);
    	glViewport(0, 0, 400, 400);
    	glBegin(GL_LINES);
    	for (int i = 0; i < length1 - 1; i++)
    	{ 
    		glVertex2d(m1[i].x, m1[i].y);
    		glVertex2d(m1[i+1].x, m1[i+1].y);
    	}
    	glVertex2d(m1[length1-1].x, m1[length1-1].y);
    	glVertex2d(m1[0].x, m1[0].y);
    	glEnd();
    	glColor3f(0.0, 1.0, 0.0);
    	glBegin(GL_LINES);
    	for (int i = 0; i < length2 - 1; i++)
    	{ 
    		glVertex2d(m2[i].x, m2[i].y);
    		glVertex2d(m2[i + 1].x, m2[i + 1].y);
    	}
    	glVertex2d(m2[length2 - 1].x, m2[length2 - 1].y);
    	glVertex2d(m2[0].x, m2[0].y);
    
    	glEnd();
    	glFlush();
    }
    void drawBack()
    { 
    	
    	glClearColor(0.0f, 0.0f, 0.0f, 0.0f);//绘图颜色为黑色 
    	glClear(GL_COLOR_BUFFER_BIT);
    	glColor3f(1.0, 1.0, 0.0);	
    	glViewport(0, 0, 400, 400);
    	glBegin(GL_LINES);
    	node *m1=new node[100],*m2=new node[100],*r1=new node[100],*r2=new node[100],*r3=new node[100],*r4=new node[100];
    	node n1(100, 100), n2(100, 200), n3(200, 200), n4(200, 100), n5(50, 150), n6(150, 220),n7(150,150);
        node ploy[3] = {  n5,n6,n7};
    	side s1(n2, n1), s2(n1, n4), s3(n4, n3), s4(n3, n2);
    	m1 = &ploy[0];
    	int nodeNum = 0;
    	r1=Sutherland(m1,m2,s1,3,nodeNum);//用第一条边裁剪剩下的图形
    	m2 = new node();
    	r2 = Sutherland(r1, m2, s2, nodeNum, nodeNum);//用第二条边裁剪剩下的图形
    	m2 = new node();
    	r3 = Sutherland(r2, m2, s3, nodeNum, nodeNum); //用第三条边裁剪剩下的
    	m2 = new node();
    	r4 = Sutherland(r3, m2, s4, nodeNum, nodeNum);//最后一条边裁剪后剩下的
    	//r1 = r2 = r3 = m1=r4=NULL;
    	//delete r1, r2, r3, m1,r4;
    	for (int i = 0; i < nodeNum - 1; i++)//画出被裁减后的图形
    	{   
    		glVertex2d(m2[i].x, m2[i].y);
    		glVertex2d(m2[i + 1].x, m2[i + 1].y);
    	}
    	glVertex2d(m2[nodeNum - 1].x, m2[nodeNum - 1].y);
    	glVertex2d(m2[0].x, m2[0].y);
    	//glVertex2d(100, 200);
    	//glVertex2d(200, 300);
    	//cout << m2[0].x << " " << m2[0].y;
    	glEnd();
    	glFlush();
    	
    }
    node *nn = new node[100];
    int nodeNumber = 0;
    void draw()
    { 
    	node n1(100, 100), n2(100, 200), n3(200, 200), n4(200, 100), n5(50, 150), n6(150, 220), n7(150, 150);
    	node ploy[3] = {  n5,n6,n7 };
    	node ploy2[4] = {  n1,n2,n3,n4 };
    	drawFront(ploy,ploy2,3,4);
    	
    	/*result=Bezier(nodeNumber,&nn[0]); glClearColor(0.0f, 0.0f, 0.0f, 0.0f);//绘图颜色为黑色 glClear(GL_COLOR_BUFFER_BIT); glColor3f(1.0, 1.0, 0.0); glViewport(0, 0, 400, 400); glBegin(GL_POINTS); for (int i = 0; i < 100; i++) { glVertex2f(result[i].x, result[i].y); //cout <<result[i].x<<" "<<result[i].y<<"\n"; } //result = NULL; //delete result; glEnd(); glColor3f(0.0, 1.0, 1.0); glViewport(0, 0, 400, 400); glBegin(GL_LINES); for (int i = 0; i < nodeNumber-1; i++) { glVertex2f(nn[i].x, nn[i].y); glVertex2f(nn[i+1].x, nn[i+1].y); } glEnd(); glFlush();*/
    
    }
    //鼠标响应函数
    void mouseClick(int btn, int state, int x, int y)
    { 
    	
    	if (btn == GLUT_LEFT_BUTTON && state == GLUT_DOWN) { 
    	node temp(x, 400-y);
    	nn[nodeNumber] = temp;
    	nodeNumber++;
    	glColor3f(0.0, 1.0, 1.0);
    	glViewport(0, 0, 400, 400);
    	glBegin(GL_POINTS);
    	glVertex2d(x,400-y);
    	glEnd();
    	glFlush();
    	}
    	if (btn == GLUT_RIGHT_BUTTON && state == GLUT_DOWN) 
    	{ 
    		node *result = new node[1000];
    		//drawFront(ploy,ploy2,3,4);
    
    		result = Bezier(nodeNumber, nn);
    		glClearColor(0.0f, 0.0f, 0.0f, 0.0f);//绘图颜色为黑色 
    		//glClear(GL_COLOR_BUFFER_BIT);
    		glColor3f(1.0, 1.0, 0.0);
    		glViewport(0, 0, 400, 400);
    		glBegin(GL_POINTS);
    		for (int i = 0; i < 1000; i++)
    		{ 
    			glVertex2f(result[i].x, result[i].y);
    
    			//cout <<result[i].x<<" "<<result[i].y<<"\n";
    		}
    		//result = NULL;
    		//delete result;
    		glEnd();
    		glColor3f(0.0, 1.0, 1.0);
    		glViewport(0, 0, 400, 400);
    		glBegin(GL_LINES);
    		for (int i = 0; i < nodeNumber - 1; i++)
    		{ 
    			glVertex2f(nn[i].x, nn[i].y);
    			glVertex2f(nn[i + 1].x, nn[i + 1].y);
    		}
    		//result = NULL;
    		nn = NULL;
    		nn = new node[100];
    		nodeNumber = 0;
    		glEnd();
    		glFlush();
    		
    
    	}
    }
    //鼠标移动函数
    void display()
    { 
    	glClearColor(0.0f, 0.0f, 0.0f, 0.0f);//绘图颜色为黑色 
        //glClear(GL_COLOR_BUFFER_BIT);
        glColor3f(1.0, 1.0, 0.0);
    	glViewport(0, 0, 400, 400);
    	LB_LineClip(50, 150, 200, 250, 100, 300, 20, 200);
    }
    int main(int argc, char * argv[])//这是使用glut库函数进行窗口管理
    { 
    	glutInit(&argc, argv);//使用glut库需要进行初始化
    	glutInitDisplayMode(GLUT_RGB | GLUT_SINGLE);//设定窗口显示模式，颜色模型和缓存，这里是RGB颜色模型和单缓存
    	glutInitWindowPosition(100, 100);//设定窗口的初始位置，屏幕左上角为原点，单位为像素
    	glutInitWindowSize(400, 400);//设定窗口的大小
    
    	glutCreateWindow("裁剪线段图形");//创建一个窗口，参数是窗口标题名 
    	Initial();
    	glutDisplayFunc(&display);//将myDisplay指定为当前窗口的显示内容函数*/
    	
    	glutCreateWindow("初始图形");//创建一个窗口，参数是窗口标题名 
    	Initial();
    	glutDisplayFunc(&draw);//将myDisplay指定为当前窗口的显示内容函数*/
    
    	glutCreateWindow("裁剪后的图");//创建一个窗口，参数是窗口标题名 
    	Initial();
    	glutDisplayFunc(&drawBack);//将myDisplay指定为当前窗口的显示内容函数 
    	glutMainLoop();//使窗口框架运行起来，使显示回调函数开始工作
    	return 0;
    }

##### 加个有关函数的头文件： #####

#pragma once
    #pragma once
    struct node//点结构 
    { 
    	double x;
    	double y;
    	node()
    	{ 
    		x = 0.0;
    		y = 0.0;
    	}
    	node(double xx, double yy)
    	{ 
    		x = xx;
    		y = yy;
    	}
    	/*node & operator=(const node& a) { node m; m.x = a.x; m.y = a.y; return m; }*/
    };
    
    struct side//边结构
    { 
    	node a;
    	node b;
    	side(node aa, node bb)
    	{ 
    		a.x = aa.x;
    		a.y = aa.y;
    		b.y = bb.y;
    		b.x = bb.x;
    	}
    	side(int n)
    	{ 
    		a.x = 0;
    		a.y = 0;
    		b.x = 0;
    		b.y = 0;
    	}
    	side()
    	{ 
    		a.x = 0;
    		a.y = 0;
    		b.x = 0;
    		b.y = 0;
    	}
    };
    
    double sideYmax(side mside)
    { 
    	if (mside.a.y < mside.b.y)
    		return mside.b.y;
    	else
    		return mside.a.y;
    }
    bool Inside(node &TestPt, side ClipBoundray)
    { 
    	if (ClipBoundray.b.x > ClipBoundray.a.x)//裁剪边为窗口下边
    	{ 
    		if (TestPt.y >= ClipBoundray.a.y)
    			return TRUE;
    	}
    	else if (ClipBoundray.b.x < ClipBoundray.a.x)//裁剪边为窗口下边
    	{ 
    		if (TestPt.y <= ClipBoundray.a.y)
    			return TRUE;
    	}
    	else if (ClipBoundray.b.y > ClipBoundray.a.y)
    		{ 
    			if (TestPt.x <= ClipBoundray.a.x)
    				return TRUE;
    		}
    	else if (ClipBoundray.b.y < ClipBoundray.a.y)
    		{ 
    			if (TestPt.x >= ClipBoundray.a.x)
    				return TRUE;
    		}
    		return FALSE;
    }
    void Intersect(node &S,node &P,side ClipBoundary,node &IntersectPt)//求两条边的交点
    { 
    	if (ClipBoundary.a.y == ClipBoundary.b.y)
    	{ 
    		IntersectPt.y = ClipBoundary.a.y;
    		IntersectPt.x = S.x + (ClipBoundary.a.y - S.y)*(P.x - S.x) / (P.y - S.y);
    	}
    	else
    	{ 
    		IntersectPt.x = ClipBoundary.a.x;
    		IntersectPt.y = S.y + (ClipBoundary.a.x - S.x)*(P.y - S.y) / (P.x - S.x);
    	}
    }
    void  Output(node P, int &Outlength, node *m2)
    { 
    	m2[Outlength] = P;
    	Outlength++;
    }
    node *Bnode(float t, int nodeNumber,node *n)//求出点集第几次后的在t分段上的点
    { 
    
    	node *temp=new node[nodeNumber-1];
    	for (int i = 0; i < nodeNumber-1; i++)
    	{ 
    		temp[i].x = (1 - t)*n[i].x + t * n[i + 1].x;
    		temp[i].y = (1 - t)*n[i].y + t * n[i + 1].y;
    	}
    	if (nodeNumber == 2)
    		return temp;
    	else
    		return Bnode(t,nodeNumber-1,temp);
    }
    node * Bezier(int nodeNumber,node * n)
    { 
    	float t = 0.0; int i = 0;
    	node *result = new node[1000];
    	for (t; t < 1; t = t + 0.001)
    	{ 
    		result[i].x = Bnode(t, nodeNumber, n)[0].x;
    		result[i].y = Bnode(t, nodeNumber, n)[0].y;
    		//result[i] = Bnode(t, nodeNumber, n)[0];
    		i++;
    		//cout << result[i].x << " " << result[i].y<<"\n";
    	}
    	return result;
    }

##### 显示效果 #####

![图形学裁剪][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM4MjQ3NTQ0_size_16_color_FFFFFF_t_70]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM4MjQ3NTQ0_size_16_color_FFFFFF_t_70]: /images/20220204/f19f7963c68c45eaba8591003477558d.png