OpenGL编码剪裁算法Cohen-Surtherland算法

#include
#include
#include

#define LEFT_EDGE 1
#define RIGHT_EDGE 2
#define BOTTOM_EDGE 4
#define TOP_EDGE 8

void LineGL(int x0,int y0,int x1,int y1)
{
	glBegin(GL_LINES);
	glColor3f(1.0f,0.0f,0.0f);		glVertex2f(x0,y0);    
	glColor3f(0.0f,1.0f,0.0f);		glVertex2f(x1,y1);		//虽然两个点的颜色设置不同，但是最终线段颜色是绿色
	glEnd();												//因为glShadeModel(GL_FLAT)设置为最后一个顶点的颜色
}															//决定整个图元的颜色。

struct Rectangle
{
	float xmin,xmax,ymin,ymax;
};

Rectangle rect;
int x0,y0,x1,y1;

int CompCode(int x,int y,Rectangle rect)
{
	int code=0x00;	//此处是二进制
	if(yrect.ymax)
		code=code|8;
	if(x>rect.xmax)
		code=code|2;
	if(x2)				//total>2,说明此函数进入死循环，是cohen-Sutherland算法的意外情况
			{
				done=1;flag=1;
			}
		}		
	}while(!done);
	
	if(accept)			//线段位于窗口内或者线段剪裁过accept=1;
		LineGL(x0,y0,x1,y1);
	else
	{
		x0=0;y=0;x1=0;y1=0;
		LineGL(x0,y0,x1,y1);
	}
		
	return accept;
}

void myDisplay()
{
	glClear(GL_COLOR_BUFFER_BIT);
	glColor3f(1.0f,0.0f,0.0f);
	glRectf(rect.xmin,rect.ymin,rect.xmax,rect.ymax);
	LineGL(x0,y0,x1,y1);
	glFlush();
}

void Init()
{
	glClearColor(0.0,0.0,0.0,0.0);
	glShadeModel(GL_FLAT);

	rect.xmin=100;
	rect.xmax=300;
	rect.ymin=100;
	rect.ymax=300;

	x0=150,y0=0,x1=50,y1=150;
	printf("Press key 'c' to Clip!\nPress key 'r' to Restore!\n");
}

void Reshape(int w,int h)
{
	glViewport(0,0,(GLsizei) w,(GLsizei) h);
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	gluOrtho2D(0.0,(GLdouble) w,0.0,(GLdouble) h);
	//printf("######Reshape\n");
}
void keyboard(unsigned char key,int x,int y)
{
	switch (key)
	{
		case 'c':
			cohensutherlandlineclip(rect,x0,y0,x1,y1);
			glutPostRedisplay();
			break;
		case 'r':
			Init();
			glutPostRedisplay();
			break;
		case 'x':
			exit(0);
			break;
		default:
			break;
	}
}

int main(int argc,char *argv[])
{
	glutInit(&argc,argv);
	glutInitDisplayMode(GLUT_RGB|GLUT_SINGLE);
	glutInitWindowPosition(100,100);
	glutInitWindowSize(640,480);
	glutCreateWindow("Hello World");

	Init();
	glutDisplayFunc(myDisplay);
	glutReshapeFunc(Reshape);
	glutKeyboardFunc(&keyboard);//按下键盘后会调用该函数，键和鼠标点击位置作为变量传给keyboard函数
	glutMainLoop();
	
	return 0;
}

#include
#include
#include

#define LEFT_EDGE 1
#define RIGHT_EDGE 2
#define BOTTOM_EDGE 4
#define TOP_EDGE 8
float ymin=100;int ymax=300;int xmin=100;int xmax=300;

struct Linea
{
	int x0;
	int y0;
	int x1;
	int y1;
};
Linea l1={l1.x0=450,l1.y0=0,l1.x1=0,l1.y1=450};
Linea l2={l2.x0=450,l2.y0=200,l2.x1=0,l2.y1=200};
Linea l3={l3.x0=200,l3.y0=0,l3.x1=200,l3.y1=450};

void LineGL(Linea &li)			//没有&，引用改变li的值
{
	glBegin(GL_LINES);
	glColor3f(1.0f,0.0f,0.0f);		glVertex2f(li.x0,li.y0);    
	glColor3f(0.0f,1.0f,0.0f);		glVertex2f(li.x1,li.y1);		//虽然两个点的颜色设置不同，但是最终线段颜色是绿色
	glEnd();												//因为glShadeModel(GL_FLAT)设置为最后一个顶点的颜色
}															//决定整个图元的颜色。

int CompCode(int x,int y)
{
	int code=0x00;	//此处是二进制
	if(yymax)
		code=code|8;
	if(x>xmax)
		code=code|2;
	if(x3)				//total>3,执行两次后total又加一
			{
				done=1;flag=1;
			}
		}		
	}while(!done);
	if(accept)		//线段位于窗口内或者线段剪裁过accept=1;
	{
		LineGL(li);
	}	
	else
	{
		li.x0=0;li.y0=0;li.x1=0;li.y1=0;
		LineGL(li);
	}	
	return accept;
}

void myDisplay()
{
	glClear(GL_COLOR_BUFFER_BIT);
	glColor3f(1.0f,0.0f,0.0f);
	glBegin(GL_LINE_LOOP);
	glVertex2f(100,100);
	glVertex2f(300,100);
	glVertex2f(300,300);
	glVertex2f(100,300);
	glEnd();
	LineGL(l1);
	LineGL(l2);
	LineGL(l3);
	glFlush();
}

void Init()
{
	glClearColor(0.0,0.0,0.0,0.0);
	glShadeModel(GL_FLAT);
	printf("Press key 'c' to Clip!\nPress key 'r' to Restore!\n");
}

void Reshape(int w,int h)
{
	glViewport(0,0,(GLsizei) w,(GLsizei) h);
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	gluOrtho2D(0.0,(GLdouble) w,0.0,(GLdouble) h);
	//printf("######Reshape\n");
}
void keyboard(unsigned char key,int x,int y)
{
	switch (key)
	{
		case 'c':
			cohensutherlandlineclip(l1);
			cohensutherlandlineclip(l2);
			cohensutherlandlineclip(l3);
			glutPostRedisplay();
			break;
		case 'r':
		l1.x0=450;l1.y0=0;l1.x1=0;l1.y1=450;
		l2.x0=450;l2.y0=200;l2.x1=0;l2.y1=200;
		l3.x0=200;l3.y0=0;l3.x1=200;l3.y1=450;
			Init();
			glutPostRedisplay();
			break;
		case 'x':
			exit(0);
			break;
		default:
			break;
	}
}

int main(int argc,char *argv[])
{
	glutInit(&argc,argv);
	glutInitDisplayMode(GLUT_RGB|GLUT_SINGLE);
	glutInitWindowPosition(100,100);
	glutInitWindowSize(640,480);
	glutCreateWindow("Hello World");

	Init();
	glutDisplayFunc(myDisplay);
	glutReshapeFunc(Reshape);
	glutKeyboardFunc(&keyboard);//按下键盘后会调用该函数，键和鼠标点击位置作为变量传给keyboard函数
	glutMainLoop();
	
	return 0;
}