Display element appears behind part of objects

OpenGL OpenGL: Basic Coding
1

Hello,

I have design an rendering an mesh object and a point. Here is the code I use:

void RenderingEngine::RenderShaded(Model *model, GLenum polyonMode,
                                   bool drawAll, bool use_position_color,
                                   bool need_to_finish) {
  glViewport(0, 0, width_, height_);

  glClear(GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT);

  if (model->IsInitialized() || drawAll) {
    Matx44f pose = model->GetPose();

    Matx44f modelViewMatrix = lookAtMatrix_ * pose;

    Matx33f normalMatrix = modelViewMatrix.get_minor<3, 3>(0, 0).inv().t();

    Matx44f modelViewProjectionMatrix = projectionMatrix_ * modelViewMatrix;

    phongblinn_shader_program_->bind();
    phongblinn_shader_program_->setUniformValue(
        "uMVMatrix", QMatrix4x4(modelViewMatrix.val));
    phongblinn_shader_program_->setUniformValue(
        "uMVPMatrix", QMatrix4x4(modelViewProjectionMatrix.val));
    phongblinn_shader_program_->setUniformValue("uNormalMatrix",
                                                QMatrix3x3(normalMatrix.val));
    phongblinn_shader_program_->setUniformValue("uLightPosition1",
                                                QVector3D(10, 10, -20));
    phongblinn_shader_program_->setUniformValue("uLightPosition2",
                                                QVector3D(-10, 10, -20));
    phongblinn_shader_program_->setUniformValue("uLightPosition3",
                                                QVector3D(0.0, 0.0, 10));
    phongblinn_shader_program_->setUniformValue("uShininess", 100.1f);
    phongblinn_shader_program_->setUniformValue("uAlpha", 0.1f);

    glPolygonMode(GL_FRONT_AND_BACK, polyonMode);

    if (polyonMode == GL_POINT) {
      glPointSize(2);
      model->Draw(phongblinn_shader_program_, use_position_color, GL_POINTS);
    } else {
      model->Draw(phongblinn_shader_program_, use_position_color);
    }
  }
  if (need_to_finish) glFinish();
}

void RenderingEngine::RenderExternalElementShaded(
    cv::Matx44f &pose, GLenum polyonMode, QOpenGLBuffer &vertex_buffer,
    QOpenGLBuffer &color_buffer, int element_size, bool need_to_finish) {
  Matx44f modelViewMatrix = lookAtMatrix_ * pose;

  Matx33f normalMatrix = modelViewMatrix.get_minor<3, 3>(0, 0).inv().t();

  Matx44f modelViewProjectionMatrix = projectionMatrix_ * modelViewMatrix;

  phongblinn_shader_program_->bind();
  phongblinn_shader_program_->setUniformValue("uMVMatrix",
                                              QMatrix4x4(modelViewMatrix.val));
  phongblinn_shader_program_->setUniformValue(
      "uMVPMatrix", QMatrix4x4(modelViewProjectionMatrix.val));
  phongblinn_shader_program_->setUniformValue("uNormalMatrix",
                                              QMatrix3x3(normalMatrix.val));
  phongblinn_shader_program_->setUniformValue("uLightPosition1",
                                              QVector3D(10, 10, -20));
  phongblinn_shader_program_->setUniformValue("uLightPosition2",
                                              QVector3D(-10, 10, -20));
  phongblinn_shader_program_->setUniformValue("uLightPosition3",
                                              QVector3D(0.0, 0.0, 10));
  phongblinn_shader_program_->setUniformValue("uShininess", 100.1f);
  phongblinn_shader_program_->setUniformValue("uAlpha", 0.1f);

  glPolygonMode(GL_FRONT_AND_BACK, polyonMode);

  vertex_buffer.bind();
  phongblinn_shader_program_->enableAttributeArray("aPosition");
  phongblinn_shader_program_->setAttributeBuffer("aPosition", GL_FLOAT, 0, 3,
                                                 sizeof(Vec3f));
  color_buffer.bind();
  phongblinn_shader_program_->enableAttributeArray("aColor");
  phongblinn_shader_program_->setAttributeBuffer("aColor", GL_FLOAT, 0, 3,
                                                 sizeof(Vec3f));

  glPointSize(60);

  glDrawElements(GL_POINTS, element_size, GL_UNSIGNED_INT, 0);

  if (need_to_finish) {
    glFinish();
  }
}

Here is the result I have:
image

First the white element should be a sphere, I don’t understand why the shader generates a square.
Then I want the sphere to be above the mesh, what should I do?