OpenGL - 渲染成纹理

我希望能够在OpenGL上将某些内容渲染成纹理，这样我可以随时进一步使用它，而无需重新渲染所有内容。这个网站给了我这样做的指南，而不使用FrameBuffer。由于兼容性问题，我不想使用 FrameBuffer 对象执行此操作，因为这台旧机器不支持它。我已经完成了一些代码，用于创建我的纹理，渲染我的场景，然后创建一个 Quad 来渲染其上的纹理。唯一的问题是纹理被渲染得像"阿尔法蒙版"，这意味着，看起来它只考虑了阿尔法值，保持我的矩形始终具有相同的颜色，但只是改变像素的透明度。这是我到目前为止完成的一些代码：

void CreateTexture ()
{
    xSize = 512;
    ySize = 512; //size of texture
//new array
    char* colorBits = new char[ xSize * ySize * 3 ];
//texture creation..
    glGenTextures(1,&texture);
    glBindTexture(GL_TEXTURE_2D,texture);
    glTexImage2D(GL_TEXTURE_2D,0 ,3 , xSize,
                 ySize, 0 , GL_RGB,
                 GL_UNSIGNED_BYTE, colorBits);
//you can set other texture parameters if you want
    glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER, GL_LINEAR);
//clean up
    delete[] colorBits;
}

然后：

int viewport[4];
    glGetIntegerv(GL_VIEWPORT,(int*)viewport);
    glViewport(0,0,xSize,ySize);

    DrawScene(hDC);
    //save data to texture using glCopyTexImage2D
    glBindTexture(GL_TEXTURE_2D,texture);
    glCopyTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA,
                     0,0, xSize, ySize, 0);
    glClearColor(.0f, 0.5f, 0.5f, 1.0f);                // Set The Clear Color To Medium Blue
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glViewport(viewport[0],viewport[1],viewport[2],viewport[3]);
    // glBindTexture(GL_TEXTURE_2D,texture);

最后：

glEnable(GL_TEXTURE_2D);                    // Enable 2D Texture Mapping
        glBlendFunc(GL_DST_COLOR,GL_ONE);               // Set Blending Mode
        glEnable(GL_BLEND);
        glClear(GL_COLOR_BUFFER_BIT);
        glBindTexture(GL_TEXTURE_2D,texture);
        glRotatef(theta, 0.0f, 0.0f, 0.01f);
        glBegin(GL_QUADS);
         //Front Face
        glTexCoord2f(0.0f, 0.0f);
        glVertex3f(-0.5, -0.5f,  0.5f);
        glTexCoord2f(1.0f, 0.0f);
        glVertex3f( 0.5f, -0.5f,  0.5f);
        glTexCoord2f(1.0f, 1.0f);
        glVertex3f( 0.5f,  0.5f,  0.5f);
        glTexCoord2f(0.0f, 1.0f);
        glVertex3f(-0.5f,  0.5f,  0.5f);
        glEnd();
        SwapBuffers(hDC);

DrawScene（） 函数只是渲染一个矩形，上面有一个三角形，每个顶点都有不同的颜色......没什么特别的。

glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
glClear(GL_COLOR_BUFFER_BIT );//| GL_DEPTH_BUFFER_BIT);
glPushMatrix();
//    glRotatef(theta, 0.0f, 0.0f, 1.0f);
glBegin(GL_QUADS);
glColor3f(1.0f, 0.0f, 0.0f);
glVertex3f(-1.0f, -1.0f,  1.0f);
glColor3f(0.0f, 1.0f, 0.0f);
glVertex3f( 1.0f, -1.0f,  1.0f);
glColor3f(0.0f, 0.0f, 1.0f);
glVertex3f( 1.0f,  1.0f,  1.0f);
glColor3f(1.0f, 1.0f, 1.0f);
glVertex3f(-1.0f,  1.0f,  1.0f);
glEnd();
glBegin(GL_TRIANGLES);
glColor3f(1.0f, 0.0f, 0.0f);
glVertex2f(0.0f,   1.0f);
glColor3f(0.0f, 1.0f, 0.0f);
glVertex2f(0.87f,  -0.5f);
glColor3f(0.0f, 0.0f, 1.0f);
glVertex2f(-0.87f, -0.5f);
glEnd();
glPopMatrix();