《基于MFC的OpenGL编程》 13 part 创建2D 和 3D 文字

本文对第11篇文章进行修改，使用显示列表来存储渲染命令。

显示列表

OpenGL provides a facility to create a preprocessed set of OpenGL commands called a display list. Creating a display list is a straight forward process. We just have to delimit the display list code with glNewList and glEndList. The display list is named by an integer and this name is used to call the list to be executed later on. Display lists are very useful for scenes which have lot of geometry that don't change in from frame to frame. If we have to rerender something that doesn't change it is not worth going through all the calculations required once again - it is better to store them somewhere in memory and reuse it. This is exactly what the display list lets us achieve. Thus if we are going to repeatedly execute the same sequence of OpenGL commands we can create and store a display list and then have this cached sequence of calls repeated with minimal overhead, since all the vertices, lighting calculations, textures and matrix operations are calculated only when the list is created and not when it is replayed. Only the results of the calculations end up being stored in display lists. This means we cannot modify the list once we create it.

1,CY457OpenGLView类中加入一个变量来保存显示列表名称

    GLuint m_sceneList;

2,创建显示列表

void CCY457OpenGLView::CreateSceneList()
{//创建显示列表
    m_sceneList = glGenLists(1);
    glNewList(m_sceneList, GL_COMPILE);
        SetupLighting();
        glEnable(GL_TEXTURE_2D);
        glBindTexture(GL_TEXTURE_2D,m_Texture[0]);
        //Front Face
        glBegin(GL_POLYGON);
            glTexCoord2f(0,0);
            glVertex3f(-1.0f,-1.0f,0.0f);
            glTexCoord2f(1,0);
            glVertex3f( 1.0f,-1.0f,0.0f);
            glTexCoord2f(1,1);
            glVertex3f( 1.0f, 1.0f,0.0f);
            glTexCoord2f(0,1);
            glVertex3f(-1.0f, 1.0f,0.0f);
        glEnd();
        //Back Face
        glBegin(GL_POLYGON);
            glTexCoord2f(1,0);
            glVertex3f(-1.0f,-1.0f,-1.0f);
            glTexCoord2f(1,1);
            glVertex3f(-1.0f, 1.0f,-1.0f);
            glTexCoord2f(0,1);
            glVertex3f( 1.0f, 1.0f,-1.0f);
            glTexCoord2f(0,0);
            glVertex3f( 1.0f,-1.0f,-1.0f);
        glEnd();
        glBindTexture(GL_TEXTURE_2D,m_Texture[1]);
        
        //Left Face
        glBegin(GL_POLYGON);
            glTexCoord2f(1,0);
            glVertex3f(-1.0f,-1.0f, 0.0f);
            glTexCoord2f(1,1);
            glVertex3f(-1.0f, 1.0f, 0.0f);
            glTexCoord2f(0,1);
            glVertex3f(-1.0f, 1.0f,-1.0f);
            glTexCoord2f(0,0);
            glVertex3f(-1.0f,-1.0f,-1.0f);
        glEnd();
        //Right Face
        glBegin(GL_POLYGON);
            glTexCoord2f(0,0);
            glVertex3f(1.0f,-1.0f, 0.0f);
            glTexCoord2f(1,0);
            glVertex3f(1.0f,-1.0f,-1.0f);
            glTexCoord2f(1,1);
            glVertex3f(1.0f, 1.0f,-1.0f);
            glTexCoord2f(0,1);
            glVertex3f(1.0f, 1.0f, 0.0f);
        glEnd();
        glBindTexture(GL_TEXTURE_2D,m_Texture[2]);
        //Top Face
        glBegin(GL_POLYGON);
            glTexCoord2f(0,0);
            glVertex3f(-1.0f, 1.0f,  0.0f);
            glTexCoord2f(0,1);
            glVertex3f( 1.0f, 1.0f,  0.0f);
            glTexCoord2f(1,1);
            glVertex3f( 1.0f, 1.0f, -1.0f);
            glTexCoord2f(1,0);
            glVertex3f(-1.0f, 1.0f, -1.0f);
        glEnd();
        //Botton Face
        glBegin(GL_POLYGON);
            glTexCoord2f(0,1);
            glVertex3f(-1.0f, -1.0f,  0.0f);
            glTexCoord2f(0,0);
            glVertex3f(-1.0f, -1.0f, -1.0f);
            glTexCoord2f(1,0);
            glVertex3f( 1.0f, -1.0f, -1.0f);
            glTexCoord2f(1,1);
            glVertex3f( 1.0f, -1.0f,  0.0f);
        glEnd();
        glDisable(GL_TEXTURE_2D);
    glEndList();
}

3，在InitializeOpenGL函数中加入对上述函数的调用：

    //创建显示列表
    CreateSceneList();

4，修改RenderScene的绘制代码

void CCY457OpenGLView::RenderScene ()
{//绘制函数
        glTranslatef(0.0f,0.0f,-5.0f);
        glRotatef(m_xRot,1.0f,0.0f,0.0f);
        glRotatef(m_yRot,0.0f,1.0f,0.0f);
        glCallList(m_sceneList);
}