OpenGL 混合功能

void RenderScene()
{
    //清除缓存区
    glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT|GL_STENCIL_BUFFER_BIT);
    
    //设置四个固定矩形颜色
    GLfloat vRed[] = {1.0f, 0.0f, 0.0f, 0.5f};
    GLfloat vGreen[] = {0.0f, 1.0f, 0.0f, 1.0f};
    GLfloat vBlue[] = {0.0f, 0.0f, 1.0f, 1.0f};
    GLfloat vBlack[] = {0.0f, 0.0f, 0.0f, 1.0f};
    
    //绘制四个固定矩形
    //GLT_SHADER_IDENTITY：单元着色器
    shaderManager.UseStockShader(GLT_SHADER_IDENTITY, vRed);
    redBatch.Draw();
    shaderManager.UseStockShader(GLT_SHADER_IDENTITY, vGreen);
    greenBatch.Draw();
    shaderManager.UseStockShader(GLT_SHADER_IDENTITY, vBlue);
    blueBatch.Draw();
    shaderManager.UseStockShader(GLT_SHADER_IDENTITY, vBlack);
    blackBatch.Draw();
    
    //移动矩形设置混合功能
    //开启混合功能
    glEnable(GL_BLEND);
    //设置混合因子
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
    //使用固定管线着色器
    shaderManager.UseStockShader(GLT_SHADER_IDENTITY, vRed);
    //绘制
    squareBatch.Draw();
    //关闭混合功能
    glDisable(GL_BLEND);
    
    //后台渲染完成交给前台
    glutSwapBuffers();
}