#include <GL/glut.h>
typedef GLfloat point2d[2];                    	//a point data type 

void triangle( point2d a, point2d b, point2d c)	//display a triangle
{
    glBegin(GL_TRIANGLES);
    glVertex2fv（a）;
    glVertex2fv（b）;
    glVertex2fv（c）;
    glEnd();
}
void display(void) 
{
    point2d v[3] = {{-1.0, -0.58}, {1.0, -0.58}, {0.0, 1.15}};
    glClear(GL_COLOR_BUFFER_BIT);
    glColor3f(0.0,0.0,1.0);  
    glLoadIdentity();
    glViewport(0, 0, 300, 400);
    triangle(v[0], v[1], v[2]); 
    glColor3f(1.0,0.0,0.0);         
    glViewport(300, 0, 300, 400);    
    glRotatef(90.0, 0.0, 0.0, 1.0); 
    triangle(v[0], v[1], v[2]);   
    glFlush();
}

void init() 
{
    glMatrixMode(GL_PROJECTION);
    gluOrtho2D(-2.0, 2.0, -2.0, 2.0);
    glMatrixMode(GL_MODELVIEW);
    glClearColor(1.0, 1.0, 1.0,1.0); 
}

void main(int argc, char **argv)
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);
    glutInitWindowSize(600, 400);
    glutCreateWindow("Triangle");

    glutDisplayFunc(display);
    init();

    glutMainLoop();
}

#include <GL/glut.h>
GLint winWidth = 600, winHeight = 600; 	//设置初始化窗口大小

/* 观察坐标系参数设置*/
GLfloat x0 = 0.0, y0= 0.0, z0 =5.0;	//设置观察坐标系原点 
GLfloat xref = 0.0, yref =0.0, zref = 0.0;	//设置观察坐标系参考点（视点） 
GLfloat Vx = 0.0, Vy = 1.0, Vz = 0.0;	//设置观察坐标系向上向量（y轴） 

/*观察体参数设置 */
//设置裁剪窗口坐标范围
GLfloat xwMin = -1.0, ywMin = -1.0, xwMax = 1.0, ywMax = 1.0;
GLfloat dnear = 1.5, dfar = 20.0;	//设置远、近裁剪面深度范围

void init (void)
{
  glClearColor(1.0,1.0,1.0,0.0);  
  
  /*①观察变换*/
   gluLookAt (x0, y0, z0, xref, yref, zref, Vx, Vy, Vz);  //指定三维观察参数
  
  /*模型变换*/
  glMatrixMode (GL_MODELVIEW);
  glScalef (2.0, 2.0, 2.0);	//比例放缩变换
  glRotatef(45.0, 0.0, 1.0, 1.0);	//旋转变换

  /*②投影变换*/
  glMatrixMode (GL_PROJECTION);
  glLoadIdentity ();

//透视投影，设置透视观察体
  glFrustum (xwMin, xwMax, ywMin, ywMax, dnear, dfar);  
}
void display (void)
{
  glClear (GL_COLOR_BUFFER_BIT);

  glColor3f (0.0, 1.0, 0.0);	//设置前景色为绿色
  glutSolidCube (1.0);	//绘制单位立方体实体
  glColor3f (0.0, 0.0, 0.0);	//设置前景色为黑色
  glLineWidth (2.0);         	//设置线宽
  glutWireCube (1.0);	//绘制单位立方体线框
  
  glFlush ();
}

void reshape (GLint newWidth, GLint newHeight)
{
  /*③视口变换 */
  glViewport (0, 0, newWidth, newHeight);	//定义视口大小

  winWidth = newWidth; 
  winHeight = newHeight;
}
void main (int argc, char** argv)
{
  glutInit (&argc, argv);
  glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB); 
  glutInitWindowPosition (100, 100); 
  glutInitWindowSize (winWidth, winHeight); 
  glutCreateWindow ("单位立方体的透视投影");

  init ();
  glutDisplayFunc (display); 
  glutReshapeFunc (reshape);
  glutMainLoop ();
}