OpenGL多邊形卡在左上角？

我正在使用theallegro庫並通過它OpenGL。啓用深度測試，則在調整大小我做的：OpenGL多邊形卡在左上角？

glEnable(GL_CULL_FACE); 
    glCullFace(GL_BACK); 
    glEnable(GL_DEPTH_TEST); 
    glMatrixMode(GL_PROJECTION); 
    glLoadIdentity(); 
    glFrustum(0,event.display.width,event.display.height,0,1,300);

然後我的畫是這樣的：

float BOX_SIZE = 200.0f; 
     glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); 


     glRotatef(0.5, 0, 0.0f, 1.0f); 
     glBegin(GL_QUADS); 

     //Top face 
     glColor3f(1.0f, 1.0f, 0.0f); 
     glNormal3f(0.0, 1.0f, 0.0f); 
     glVertex3f(500 + -BOX_SIZE/2, BOX_SIZE/2, -BOX_SIZE/2); 
     glVertex3f(500 + -BOX_SIZE/2, BOX_SIZE/2, BOX_SIZE/2); 
     glVertex3f(500 + BOX_SIZE/2, BOX_SIZE/2, BOX_SIZE/2); 
     glVertex3f(500 + BOX_SIZE/2, BOX_SIZE/2, -BOX_SIZE/2); 

     //Bottom face 
     glColor3f(1.0f, 0.0f, 1.0f); 
     glNormal3f(0.0, -1.0f, 0.0f); 
     glVertex3f(-BOX_SIZE/2, -BOX_SIZE/2, -BOX_SIZE/2); 
     glVertex3f(BOX_SIZE/2, -BOX_SIZE/2, -BOX_SIZE/2); 
     glVertex3f(BOX_SIZE/2, -BOX_SIZE/2, BOX_SIZE/2); 
     glVertex3f(-BOX_SIZE/2, -BOX_SIZE/2, BOX_SIZE/2); 

     //Left face 
     glNormal3f(-1.0, 0.0f, 0.0f); 
     glColor3f(0.0f, 1.0f, 1.0f); 
     glVertex3f(-BOX_SIZE/2, -BOX_SIZE/2, -BOX_SIZE/2); 
     glVertex3f(-BOX_SIZE/2, -BOX_SIZE/2, BOX_SIZE/2); 
     glColor3f(0.0f, 0.0f, 1.0f); 
     glVertex3f(-BOX_SIZE/2, BOX_SIZE/2, BOX_SIZE/2); 
     glVertex3f(-BOX_SIZE/2, BOX_SIZE/2, -BOX_SIZE/2); 

     //Right face 
     glNormal3f(1.0, 0.0f, 0.0f); 
     glColor3f(1.0f, 0.0f, 0.0f); 
     glVertex3f(BOX_SIZE/2, -BOX_SIZE/2, -BOX_SIZE/2); 
     glVertex3f(BOX_SIZE/2, BOX_SIZE/2, -BOX_SIZE/2); 
     glColor3f(0.0f, 1.0f, 0.0f); 
     glVertex3f(BOX_SIZE/2, BOX_SIZE/2, BOX_SIZE/2); 
     glVertex3f(BOX_SIZE/2, -BOX_SIZE/2, BOX_SIZE/2); 

     glEnd(); 

     glEnable(GL_TEXTURE_2D); 

     glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); 
     glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); 
     glColor3f(1.0f, 1.0f, 1.0f); 
     glBegin(GL_QUADS); 

     //Front face 
     glNormal3f(0.0, 0.0f, 1.0f); 
     glTexCoord2f(0.0f, 0.0f); 
     glVertex3f(-BOX_SIZE/2, -BOX_SIZE/2, BOX_SIZE/2); 
     glTexCoord2f(1.0f, 0.0f); 
     glVertex3f(BOX_SIZE/2, -BOX_SIZE/2, BOX_SIZE/2); 
     glTexCoord2f(1.0f, 1.0f); 
     glVertex3f(BOX_SIZE/2, BOX_SIZE/2, BOX_SIZE/2); 
     glTexCoord2f(0.0f, 1.0f); 
     glVertex3f(-BOX_SIZE/2, BOX_SIZE/2, BOX_SIZE/2); 

     //Back face 
     glNormal3f(0.0, 0.0f, -1.0f); 
     glTexCoord2f(0.0f, 0.0f); 
     glVertex3f(-BOX_SIZE/2, -BOX_SIZE/2, -BOX_SIZE/2); 
     glTexCoord2f(1.0f, 0.0f); 
     glVertex3f(-BOX_SIZE/2, BOX_SIZE/2, -BOX_SIZE/2); 
     glTexCoord2f(1.0f, 1.0f); 
     glVertex3f(BOX_SIZE/2, BOX_SIZE/2, -BOX_SIZE/2); 
     glTexCoord2f(0.0f, 1.0f); 
     glVertex3f(BOX_SIZE/2, -BOX_SIZE/2, -BOX_SIZE/2); 

     glEnd(); 
     glDisable(GL_TEXTURE_2D); 
//code goes here 
al_flip_display();

出於某種原因立方體不管我怎麼翻譯好像從0,0和擴展theres總是一個頂點在0,0。我做錯了什麼？謝謝

來源

2010-06-17 jmasterx

我不知道allegro庫的任何細節，但在閱讀代碼片段時想到兩件事情。

你爲什麼不叫 glViewport(event.display.width,event.display.height) 在調整大小？ glFrustum調用通常不應該依賴於顯示器大小。
你有沒有打電話給 glMatrixMode(GL_MODELVIEW)？否則將所有矩陣運算應用於投影矩陣。

我希望有幫助。

來源

2010-06-17 06:22:15

OpenGL多邊形卡在左上角？

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