在OpenGL(C++)中绘制三维场景中的二维文本

Question

我正在OpenGL中尝试3D图形，并成功创建了一个3D级别。然而，我也想在屏幕上显示一些2D文本，这些文本保持不变（类似于你在第一人称射击游戏中看到的HP或弹药统计）。这是我用来渲染关卡的整个方法。除了文本（根本不会出现在屏幕上）之外，一切都按照我的意愿进行。如何使文本正确显示？

void render_Scene(void)
{
    int i;
    int j;
    glClearColor(0.0, 0.0, 0.0, 1.0);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glLoadIdentity();

    //Camera perspective
    gluLookAt(x, y, 1.0, x + lx, y + ly, 1.0, 0.0, 0.0, 1.0);
    glColor3f(0.4, 0.4, 0.4);

    //Draw walls around the level
    glEnable(GL_TEXTURE_2D);
    glBindTexture(GL_TEXTURE_2D, wall_Texture);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glBegin(GL_QUADS);
    glNormal3f(0.0, 1.0f, 0.0f);
    glTexCoord2f(0.0f, 0.0f);
    glVertex3f(-75, -75, 0);
    glTexCoord2f(1.0f, 0.0f);
    glVertex3f(-75, -75, 1.2);
    glTexCoord2f(1.0f, 1.0f);
    glVertex3f(75, -75, 1.2);
    glTexCoord2f(0.0f, 1.0f);
    glVertex3f(75, -75, 0);
    glEnd();
    glBegin(GL_QUADS);
    glNormal3f(0.0, 1.0f, 0.0f);
    glTexCoord2f(0.0f, 0.0f);
    glVertex3f(-75, 72, 0);
    glTexCoord2f(1.0f, 0.0f);
    glVertex3f(-75, 72, 1.2);
    glTexCoord2f(1.0f, 1.0f);
    glVertex3f(75, 72, 1.2);
    glTexCoord2f(0.0f, 1.0f);
    glVertex3f(75, 72, 0);
    glEnd();
    glBegin(GL_QUADS);
    glNormal3f(0.0, 1.0f, 0.0f);
    glTexCoord2f(0.0f, 0.0f);
    glVertex3f(-75, -75, 0);
    glTexCoord2f(1.0f, 0.0f);
    glVertex3f(-75, 72, 0);
    glTexCoord2f(1.0f, 1.0f);
    glVertex3f(-75, 72, 1.2);
    glTexCoord2f(0.0f, 1.0f);
    glVertex3f(-75, -75, 1.2);
    glEnd();
    glBegin(GL_QUADS);
    glNormal3f(0.0, 1.0f, 0.0f);
    glTexCoord2f(0.0f, 0.0f);
    glVertex3f(75, -75, 0);
    glTexCoord2f(1.0f, 0.0f);
    glVertex3f(75, 72, 0);
    glTexCoord2f(1.0f, 1.0f);
    glVertex3f(75, 72, 1.2);
    glTexCoord2f(0.0f, 1.0f);
    glVertex3f(75, -75, 1.2);
    glEnd();
    glDisable(GL_TEXTURE_2D);

    //Draw ground texture
    for (int m = -150; m <= 140; m += 10)
    {
        for (int n = -150; n <= 140; n += 10)
        {
             glEnable(GL_TEXTURE_2D);
             glBindTexture(GL_TEXTURE_2D, ground_Texture);
             glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
             glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
             glBegin(GL_QUADS);
             glNormal3f(0.0, 1.0f, 0.0f);
             glTexCoord2f(0.0f, 0.0f);
             glVertex3f(n, m, 0.0);
             glTexCoord2f(1.0f, 0.0f);
             glVertex3f(n, m + 10, 0.0);
             glTexCoord2f(1.0f, 1.0f);
             glVertex3f(n + 10, m + 10, 0.0);
             glTexCoord2f(0.0f, 1.0f);
             glVertex3f(n + 10, m, 0.0);
             glEnd();
             glDisable(GL_TEXTURE_2D);
         }
    }

    //Draw trees in level (uses a seperate method)
    for (i = -9; i < 9; i++)
    {
         for (j = -9; j < 9; j++)
         {
             glPushMatrix();
             glTranslatef(i*7.5, j*7.5, 0);
             draw_Trees();
             glPopMatrix();
         }
    }
    //Create light
    GLfloat lightColor0[] = { 1.0, 1.0f, 1.0f, 1.0f };
    GLfloat lightPos0[] = { lx, ly, deltaMove, 1.0f };
    glLightfv(GL_LIGHT0, GL_DIFFUSE, lightColor0);
    glLightfv(GL_LIGHT0, GL_POSITION, lightPos0);

    //Here's where I'm trying to render the text (I've heard that glPushAttrib and glPopAttrib may be important for this part) but it does not appear anywhere on the screen
    glColor3f(1.0, 1.0, 1.0);
    glPushMatrix();
    glPushAttrib(GL_LIGHTING);
    glDisable(GL_TEXTURE_2D);
    glDisable(GL_LIGHTING);
    glLoadIdentity();
    glRasterPos2i(10, 30);
    void * font = GLUT_BITMAP_8_BY_13;
    for (string::iterator i = strings[stage].begin(); i != strings[stage].end(); ++i)
    {
        glutBitmapCharacter(font, *i);
    }
    glPopAttrib();
    glPopMatrix();
    glutSwapBuffers();
}  

编辑：有人告诉我应该使用glWindowPos2i而不是glRasterPos2i。此解决方案的问题是glWindowPos2i未被识别，并导致生成错误。在一些在线研究之后，我添加了以下代码行：

PFNGLWINDOWPOS2IPROC glWindowPos2i;
glWindowPos2i = (PFNGLWINDOWPOS2IPROC)glutGetProcAddress("glWindowPos2i");

现在程序可以正常运行，但当我尝试使用glWindowPos2i函数时，它会崩溃。我使用和作为包含的标头，以防有人提出解决方案，使glWindowPos2i正常工作。

Answer 1

使用glWindowPos2i而不是glRasterPos2i。glRasterPos2i使用世界坐标中的位置。glWindowPos2i使用屏幕坐标中的位置。https://www.opengl.org/sdk/docs/man2/xhtml/glWindowPos.xmlhttps://www.opengl.org/sdk/docs/man2/xhtml/glRasterPos.xml