一个简单的场景观察程序(OpenGL)

 

/**/ /*
旭东 2006.4
创建窗口、键盘响应等实现均采用glut库函数.
函数说明：
void DrawGroud()    绘制网格地面.
void AirRoam()      设置gluLookAt ，此函数为学习重点， 来源于www.GameRes.com
*/


#include  " windows.h "
#include  " gl/gl.h "
#include  " gl/glut.h "
#include  " math.h "
#define  KEY_DOWN(vk_code)((GetAsyncKeyState(vk_code) & 0x8000) ? 1 : 0)

void  DrawGroud() // 绘制网格地面
... {
    glPushMatrix();
    glColor3f(0.5,0.7,1.0);
    glTranslatef(0.0,-20.0,0.0); 
    glBegin(GL_LINES);
    for(int i=-300;i<=300;i=i+5)
    ...{
        glVertex3f(-i,0,-300);
        glVertex3f(-i,0,300);
    }
    for(int j=-300;j<=300;j+=5)
    ...{
        glVertex3f(-300,0,-j);
        glVertex3f(300,0,-j);
    }
    glEnd();
    glPopMatrix();
}


void  AirRoam( void )
... {

    // 追踪观察点的方向
    static GLfloat s_eye[] = ...{ 0, 8.0, 0};
    static GLfloat s_at[]  = ...{ 0.0, 0.0, 0.0 };
    static GLfloat s_angle = -90.0;
    float speed = 1.3f;
    float PI=3.14159f;

    // 旋转请求
    if (KEY_DOWN(VK_LEFT))
    ...{
        s_angle -= 2.0;
    }
    if (KEY_DOWN(VK_RIGHT))
    ...{
        s_angle += 2.0;
    }
    float rad =  float(PI*s_angle/180.0f);

    // 前进,后退请求
    if (KEY_DOWN(VK_UP))
    ...{
        s_eye[2] += (float)sin(rad) * speed;
        s_eye[0] += (float)cos(rad) * speed;
    }
    if (KEY_DOWN(VK_DOWN))
    ...{
        s_eye[2] -= (float)sin(rad) * speed;
        s_eye[0] -= (float)cos(rad) * speed;
    }

    // 观察点
    s_at[0] = float(s_eye[0] + 100*cos(rad));
    s_at[2] = float(s_eye[2] + 100*sin(rad));
    s_at[1] = s_eye[1];

    //设置观察点
    glLoadIdentity();
    gluLookAt(s_eye[0],s_eye[1],s_eye[2],
        s_at[0],s_at[1],s_at[2],
        0.0, 1.0, 0.0);
    glutPostRedisplay();
}

void  RenderScene( void )
... {
    glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
    DrawGroud();
    AirRoam();
    glutSwapBuffers();
}
void  SetupRC( void )
... {
    glEnable(GL_DEPTH_TEST);
    glColor3f(1.0,0.0,0.0);
    glClearColor(0.0f, 0.0f, 1.0f, 1.0f);
}

void  ChangeSize(GLsizei w,GLsizei h)
... {
    if(h==0)
        h=1;
    glViewport(0,0,w,h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluPerspective(60.0f,(float)w/(float)h,1.0f,200.0f);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    glTranslatef(0.0f, 0.0f, -50.0f); 
}


void  main()
... {
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB|GLUT_DEPTH);
    glutInitWindowSize(800,600);
    glutCreateWindow("Simple");
    glutDisplayFunc(RenderScene);
    glutReshapeFunc(ChangeSize);
    SetupRC();
    glutMainLoop();
}