键盘回调函数的使用

#include <GL/glut.h> 
#include<stdio.h>
#include <math.h>

#define DEG_TO_RAD 0.017453  //角度转为弧度的参数，即 2*PI/360

 
GLboolean rotate = GL_TRUE;
float theta=30.0; //直线与X轴正方向的夹角

float length=200.0;  //直线的长度

float x=300.0, y=200.0; //直线的第一个端点

 

void init (void)

{

    glClearColor (1.0, 1.0, 1.0, 0.0); 

    glMatrixMode (GL_PROJECTION);      

    gluOrtho2D (0.0, 640.0, 0.0, 480.0);

}

 

void display (void)

{

    glClear (GL_COLOR_BUFFER_BIT); 

 

    glColor3f (1.0, 0.0, 0.0);     

    glBegin (GL_POLYGON);

        glVertex2f (x, y);     

        glVertex2f ( x + length*cos(DEG_TO_RAD*theta),

 y + length*sin(DEG_TO_RAD*theta) );

              glVertex2f ( x + length*cos(DEG_TO_RAD* (theta+30) ),

y + length*sin(DEG_TO_RAD* (theta+30)) );

    glEnd ( );

    glutSwapBuffers ( );     //交换前后台缓存

}

 

void myKeyboard(unsigned char key,  int x, int y)

{

       if(key == 'a' || key == 'A')

              theta += 5.0;

       if(key == 's' || key == 'S')

              theta -= 5.0;

    if(key == 'c' || key == 'C')

              exit(0);

       if (theta>360) theta -=360;

       if (theta<0) theta +=360;

       glutPostRedisplay(); //重新调用绘制函数

}

void main (int argc, char** argv)

{

    glutInit (&argc, argv);                        

       glutInitDisplayMode (GLUT_DOUBLE | GLUT_RGB); 

    glutInitWindowPosition (100, 100);  

    glutInitWindowSize (640, 480);     

    glutCreateWindow("Draw Triangle with Double Buffer");
	init();                           

    glutDisplayFunc (display);      

  glutKeyboardFunc( myKeyboard);

    glutMainLoop ( );                  

}

通过键盘控制曲线的粗细

#include<GL/glut.h>
#include <math.h>
#define PI 3.14
GLint size = 1;
void drawMyLines()
{
	float t;
	float x,y,z;
	float a=2,b=3,c=18;
	glColor3f(1.0,0.5,0.5);
	glLineWidth(size);
	glBegin(GL_LINE_STRIP);
		for(t=0.0;t<=2*PI;t+=0.0002)
		{
			x=a*t*cos(c*t)+b;
			y=a*t*sin(c*t)+b;
			z=c*t;
			glVertex3f(x,y,z);
		}
	glEnd();
    glLineWidth(1);
	glColor3f(1.0,1.0,1.0);
	glBegin(GL_LINES);  //建立坐标轴
		glVertex3f(0,0,0);
		glVertex3f(12,0,0);
	glEnd();
	glBegin(GL_LINES);  //建立坐标轴
         glVertex3f(0,0,0);
		glVertex3f(0,0,12);
	glEnd();
	glBegin(GL_LINES);  //建立坐标轴
		glVertex3f(0,0,0);
		glVertex3f(0,12,0);
	glEnd();
}
void display()
{
	glClear(GL_COLOR_BUFFER_BIT);
	drawMyLines();    //调用drawMyLines函数
			
	glFlush();
}
void myKeyboard(unsigned char key,int x,int y)
{
   switch(key)
	     
   {
   case '1':
	   size++;
	   break;
   case '2':
	   size--;
	   break;
   }
   glutPostRedisplay();
}
void init()
{
	glClearColor(0.0,0.0,0.0,0.0);

	glColor3f(1.0,1.0,1.0);
    
	gluLookAt(1,1,1,   //更改视角
		3,3,3,
		-1,-1,1
		);

	glMatrixMode(GL_PROJECTION);  //设置投影模式
	glLoadIdentity();            //设置单位矩形
	glOrtho(-12.0,12.0,-12.0,12.0,-12,12);

}


int main(int argc, char* argv[])
{
	 
    glutInit(&argc, argv);

	glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
    glutInitWindowSize(500, 500);
	glutInitWindowPosition(0, 0);
	glutCreateWindow("Simple");

	glutDisplayFunc(display);
    
	init();
      glutKeyboardFunc(myKeyboard);
	glutMainLoop();   //使程序一直处在监听状态中
        
  
	return 0;
}