奇OpenGL的行爲繪製一個立方體

Question

當我畫一個立方體與此代碼

glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); 
glLoadIdentity(); 
gluLookAt(
x, y, z, 
x+xp, y+yp, z+zp, 
0.0f, 1.0f, 0.0f); 
glBegin(GL_QUADS);    

glColor3f(0.0f,1.0f,0.0f);    
glVertex3f(1.0f, 1.0f,-1.0f);   
glVertex3f(-1.0f, 1.0f,-1.0f);  
glVertex3f(-1.0f, 1.0f, 1.0f);  
glVertex3f(1.0f, 1.0f, 1.0f);   

glColor3f(1.0f,0.5,0.0f);   
glVertex3f(1.0f,-1.0f, 1.0f);   
glVertex3f(-1.0f,-1.0f, 1.0f);   
glVertex3f(-1.0f,-1.0f,-1.0f);  
glVertex3f(1.0f,-1.0f,-1.0f);   

glColor3f(1.0f,0.0f,0.0f);    
glVertex3f(1.0f, 1.0f, 1.0f);   
glVertex3f(-1.0f, 1.0f, 1.0f);  
glVertex3f(-1.0f,-1.0f, 1.0f);   
glVertex3f(1.0f,-1.0f, 1.0f);   

glColor3f(1.0f,1.0f,0.0f);    
glVertex3f(1.0f,-1.0f,-1.0f);   
glVertex3f(-1.0f,-1.0f,-1.0f);   
glVertex3f(-1.0f, 1.0f,-1.0f);   
glVertex3f(1.0f, 1.0f,-1.0f);   

glColor3f(0.0f,0.0f,1.0f);    
glVertex3f(-1.0f, 1.0f, 1.0f);  
glVertex3f(-1.0f, 1.0f,-1.0f);   
glVertex3f(-1.0f,-1.0f,-1.0f);  
glVertex3f(-1.0f,-1.0f, 1.0f);   

glColor3f(1.0f,0.0f,1.0f);    
glVertex3f(1.0f, 1.0f,-1.0f);   
glVertex3f(1.0f, 1.0f, 1.0f);   
glVertex3f(1.0f,-1.0f, 1.0f);  
glVertex3f(1.0f,-1.0f,-1.0f); 
glEnd(); 

我得到一個奇怪的cude繪圖：

和

即使沒有gluLookAt（）我仍然結束一張奇怪的圖畫。

奇怪的是我在python OpenGL項目中使用了完全相同的代碼，並且沒有任何問題。所以它似乎是一個C錯誤？

它似乎也是第一個2個四邊形（綠色和橙色）沒有被繪製。

Answer 1

加入正好解決我自己的問題：

glEnable(GL_DEPTH_TEST); 

我的代碼。