glDrawArrays在原點繪製隨機點？

我有幾個對象是通過三角形粉絲繪製的，但是一旦我設置了我的glVertexPointer並調用了glDrawArrays，我始終沒有指定至少顯式指定原點的一個點。以下是我如何繪製場景。 DrawScene函數被設置爲一個定時器，每30ms調用一次。glDrawArrays在原點繪製隨機點？

// initialize openGL scene 
    InitializeGL(){ 
    glViewport(0, 0, 800, 600); 
    glEnable(GL_MULTISAMPLE); 
    glClearDepth(1.0f); 
    glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_FASTEST); 
    glShadeModel(GL_FLAT); 
    glEnable(GL_DEPTH_TEST); 
    glEnable(GL_CULL_FACE); 
    glClearColor(0.0f,0.0f,0.0f,0.0f); 
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); 

    setUpView() // optional makes a call to glRotate() and glTranslate() in MODELVIEW matrix mode 

    drawAxis() //optional method to draw x,y,z axis 

    startDrawSceneTimer() // method that just starts the DrawScene timer to 30ms 

    } 


    DrawScene() 
    { 
     glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); 
     glPolygonMode(GL_FRONT_AND_BACK, GL_FILL); 
     glEnable(GL_VERTEX_ARRAY); 
     //poly2 is a 7 point sided polygon, array is pointX, pointY, pointZ of each vertex 
     GLfloat poly2 [21] ={ -761.805 , 0.0 , 165.184 , -750.39 , 0.0 , 160.456 , 
     -745.47 , 0.0 , 160.456 , -745.47 , 0.0 , 170.298 , -749.425 , 0.0 , 177.359 , 
     -755.31 , 0.0 , 180.141 , -765.155 , 0.0 , 177.421}; 
     glVertexPointer(3,GL_FLOAT,0,poly2); 
     glDrawArrays(GL_TRIANGLE_FAN,0,21); 
     glDisable(GL_VERTEX_ARRAY); 
    }

在圖像的左下象限中只有一個多邊形，類似於六邊形。與起源的長期聯繫是異常現象。我的頂點「poly2」數組不包含頂點（0,0,0）。

這裏是我得到的圖像：