如何在OpenGL中绘制一个立方体？

Question

I need a help. I have found several solutions to draw cube in OpenGl, but I have a problem.

My code is:

    wglMakeCurrent(pDC->m_hDC, m_hrc);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();

glTranslatef(1.5f, 0.0f, -7.0f);  // Move right and into the screen

glBegin(GL_QUADS);                // Begin drawing the color cube with 6 quads
                                  // Top face (y = 1.0f)
                                  // Define vertices in counter-clockwise (CCW) order with normal pointing out
glColor3f(0.0f, 1.0f, 0.0f);     // Green
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);

// Bottom face (y = -1.0f)
glColor3f(1.0f, 0.5f, 0.0f);     // Orange
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);

// Front face  (z = 1.0f)
glColor3f(1.0f, 0.0f, 0.0f);     // Red
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);

// Back face (z = -1.0f)
glColor3f(1.0f, 1.0f, 0.0f);     // Yellow
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);

// Left face (x = -1.0f)
glColor3f(0.0f, 0.0f, 1.0f);     // Blue
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);

// Right face (x = 1.0f)
glColor3f(1.0f, 0.0f, 1.0f);     // Magenta
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();  // End of drawing color-cube

glFlush();                  

SwapBuffers(pDC->m_hDC);
wglMakeCurrent(NULL, NULL);

Bellow is the image I want to get and the image I get. expected image and the image I get

How to solve this problem? Thanks in advance.

Answer 1

You'll have to enable depth testing. Otherwise triangles are drawn in the order the are given in code which leads to overdraws even if a triangle is behind another one. To enable depth-testing call

glEnable(GL_DEPTH_TEST);

before issuing the first draw-call.