我在z=0上画了两个三角形，从上方居中漫射光照。如果我在z轴上缩放其中一个，它会改变光照。由于z=0，我认为在z轴上缩放不会有任何影响。
我错过了什么？

渲染代码

// Set up the a light centered horizontally.
  glEnable(GL_LIGHTING);
  glEnable(GL_LIGHT0);
  float light1Position[] = { 0.0f, 2.0f, 0.0f, 1.0f };
  float light1Diffuse[] = { 1.0f, 1.0f, 1.0f, 1.0f };
  glLightfv(GL_LIGHT0, GL_POSITION, light1Position);
  glLightfv(GL_LIGHT0, GL_DIFFUSE, light1Diffuse);

  // Set up the material.
  float material1Diffuse[] = { 1.0f, 1.0f, 1.0f, 1.0f };
  glMaterialfv(GL_FRONT, GL_DIFFUSE, material1Diffuse);

  // Transform such that we can draw in (-1, -1) to (1, 1) at z = 0.
  glTranslated(0, 0, -1);
  glScaled(2, 2, 1);

  // Draw two triangles, symmetric w.r.t. to the light and camera.
  glBegin(GL_TRIANGLES);
    glVertex3d(-1, -1,  0);
    glVertex3d( 0,  1,  0);
    glVertex3d(-1,  1,  0);
  glEnd();

  glScaled(1, 1, 5.0);  // This should be a no-op since 5 * 0 = 0.
                        // However, the following triangle is darker.
  glBegin(GL_TRIANGLES);
    glVertex3d( 1, -1,  0);
    glVertex3d( 1,  1,  0);
    glVertex3d( 0,  1,  0);
  glEnd();

渲染结果

我已经上传了一个Cocoa项目来表示这个on github，我已经在Objective-C和C++中尝试过了。