引擎测试：在屏幕上渲染立方体（OpenGL）

Question

首先，我想说明我在这里所做的只是试图测试我的OpenGL知识的能力，仅此而已。

以下代码表示一个无限循环，它可以在屏幕上呈现立方体，然后将其保留在静态投影中。无论出于何种原因，它都拒绝展示。最重要的是，我没有使用白色背景色，而是使用黑色背景色。

代码

MainLoop语句

const int FIELD_OF_VIEW_Y = 60; 

     glMatrixMode(GL_PROJECTION); 
     glLoadIdentity(); 

     gluPerspective(FIELD_OF_VIEW_Y, 640.0/480.0, 1.0, 1028); 

     glMatrixMode(GL_MODELVIEW); 

     glTranslatef(0.0, 0.0, -2.0f); 

     Vector3f cam(0, 0, 0); 

     QPoint3F position(3, 3, 3); 

     const double CUBE_SIZE = 1; 

     while(true) 
     { 
      while(SDL_PollEvent(mEvent)) 
      { 
       TestCubeRender(CUBE_SIZE, cam, position); 
       mControls->DoKeyHandling(mEvent); 
       mCamera->ReceiveInput(mEvent->key); 
       mCamera->UpdateCamera(); 
      } 
     } 

TestCubeRender

void TestCubeRender(const double size, const Vector3f& cameraPos, const QPoint3F& position) 
    { 
     glClear(GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT); 

     glClearColor(1, 1, 1, 1); 

     int x1 = 0, x2 = 0; 
     int y1 = 0, y2 = 0; 
     int z1 = 0, z2 = 0; 

     x1 = (position.x() - size); 
     x2 = position.x() + size; 

     y1 = (position.y() - size); 
     y2 = position.y() + size; 

     z1 = (position.z() - size); 
     z2 = position.z() + size; 

     qreal camZ = cameraPos.Z; 
     qreal camY = cameraPos.Y; 
     qreal camX = cameraPos.X; 

     glMatrixMode(GL_PROJECTION); 

     //glOrtho(0.0, 0.0, 0.0, 0.0, 0.0, 0.0); 

     glMatrixMode(GL_MODELVIEW); 
     glPushMatrix(); 

     //glTranslatef(0.0, 0.0, -10.0); 

     /* 
     * if axis > mCamera.axis; then normal3f -1.0 on the axis. 
     *  axis point is axis1 
     * else if axis < mCamera.axis; then nomral3f 1.0 on the axis. 
     *  axis point is axis2 
     */ 

     /* Pattern: one axis is written twice, with the other variant of the same axis written twice as well, then the 
     * order at which those axes are written is flipped, yet still following the same pattern. 
     * Pattern2: one type of axis is still written twice, and the other group of the same axis written twice as well, 
     * the only difference being that the first group is written once, with the next group written twice, and then that 
     * first group written once again. The third axis type is written using one type, depending on the camera comparisons. 
     */ 

     glBegin(GL_QUADS); 

     glColor4f(1.0, 0, 1, 1); 

     if (z1 <= camZ) 
     { 
      glNormal3f(0.0, 0.0, -1.0); 
      glVertex3i(x1, y1, z1); //1 
      glVertex3i(x1, y2, z1); //1 
      glVertex3i(x2, y2, z1); //1 
      glVertex3i(x2, y1, z1); //1 
     } 

     if (z2 >= camZ) 
     { 
      glNormal3f(0.0, 0.0, 1.0); 
      glVertex3i(x2, y1, z2); //2 
      glVertex3i(x2, y2, z2); //2 
      glVertex3i(x1, y2, z2); //2 
      glVertex3i(x1, y1, z2); //2 
     } 

     glColor4f(0, 1, 0, 1); 

     if (y1 >= camY) 
     { 
      glNormal3f(0.0, -1.0, 0.0); 
      glVertex3i(x2, y1, z1); 
      glVertex3i(x2, y1, z2); 
      glVertex3i(x1, y1, z2); 
      glVertex3i(x1, y1, z1); 
     } 

     if (y2 <= camY) 
     { 
      glNormal3f(0.0, 1.0, 0.0); 
      glVertex3i(x1, y2, z1); 
      glVertex3i(x1, y2, z2); 
      glVertex3i(x2, y2, z2); 
      glVertex3i(x2, y2, z1); 
     } 

     glColor4f(1, 0, 0, 1); 

     if (x1 >= camX) 
     { 
      glNormal3f(-1.0, 0.0, 0.0); 
      glVertex3i(x1, y1, z1); 
      glVertex3i(x1, y1, z2); 
      glVertex3i(x1, y2, z2); 
      glVertex3i(x1, y2, z1); 
     } 

     if (x2 <= camX) 
     { 
      glNormal3f(1.0, 0.0, 0.0); 
      glVertex3i(x2, y2, z1); 
      glVertex3i(x2, y2, z2); 
      glVertex3i(x2, y1, z2); 
      glVertex3i(x2, y1, z1); 
     } 

     glEnd(); 

     glPopMatrix(); 
    } 

我已经调试和调试这很多很多次。我知道值应该至少显示东西。如果我甚至可以看到我的背景颜色变化，我至少知道正在做某件事。 我该怎么办？

Answer 1

缺少两件事：将视口（glViewport）设置为窗口内部大小。渲染后交换缓冲区（SDL_GL_SwapBuffers）。