wglUseFontBitmaps函数
The wglUseFontBitmaps() function creates a set of bitmap display lists based on the glyphs in the currently selected font in the current DC for use in the current OpenGL RC. It basically creates a series of sequential display lists which can be executed using the function glCallLists. The function takes care of aligning the raster positions of subsequent bitmaps once we specify the raster position for the first bitmap. We use the glRasterPos function to set the current raster position, where the bitmapped text would start appearing.
The glRasterPos function works exactly the same way as glVertex function, the only difference being that the position is being transformed and not the object. Thus when we use wglUseFontBitmaps to generate display lists and then call them, the resulting text is displayed, starting at the current raster position, and the bitmaps are copied to the raster buffer, giving the effect of always having the text positioned in the xy plane of the screen.
Thus we would use wglUseFontBitmaps when we need the text to be visible to the user and that the size of the text relative to its distance from the viewpoint doesn't matter.
wglUseFontOutlines函数
The wglUseFontOutlines function creates a set of 3D polygon or line based primitive display lists, based on the glyphs in the currently selected TrueType font in the current DC for use in the current OpenGL RC. Stroke and Raster fonts are not supported. These objects can then be used to draw 3D characters. This function also has additional arguments that control the extrusion of the 3D characters in the +Z direction, the deviation of the generated primitive vertices from the design outline of the font, whether to generated filled polygons or a wireframe primitives and an array of structures to hold the metrics of each of the generated characters.
1，在CCY457OpenGLView类中加入下述变量：
//For Text
GLuint m_3DTextList;
GLuint m_2DTextList;
BOOL m_b3DText, m_b2DText;
并在构造函数中进行初始化：
CCY457OpenGLView::CCY457OpenGLView()
{
m_xRot = 0.0f;
m_yRot = 0.0f;
m_b3DText = FALSE;
m_b2DText = FALSE;
}
2，加入两个用来创建文本的菜单项及其事件处理函数
void CCY457OpenGLView::OnText2dtext()
{
m_b3DText = FALSE;
m_b2DText = TRUE;
InvalidateRect(NULL,FALSE);
}
void CCY457OpenGLView::OnText3dtext()
{
m_b3DText = TRUE;
m_b2DText = FALSE;
InvalidateRect(NULL,FALSE);
}
void CCY457OpenGLView::OnUpdateText2dtext(CCmdUI* pCmdUI)
{
pCmdUI->SetRadio(m_b2DText);
}
void CCY457OpenGLView::OnUpdateText3dtext(CCmdUI* pCmdUI)
{
pCmdUI->SetRadio(m_b3DText);
}