Builder and alpha channel

[dov]

I'm trying to add an "overlay" by a second vsg::View that should contain a rectangle. Eventually, I will control this rectangle for selection by the mouse. As a shortcut I tried to use the builder and a quat for the rectangle, but what confuses me is that the the alpha channel of the color was not honored, and the rectangle was drawn opaque. Is there a some (state?) setting that can be used to get alpha transparency. Or do I have to write my own shader to get a transparent rectangle?

Here is the code that I used:

    // Create an another view that will be use for the selection
    auto static_camera = vsg::Camera::create(
      vsg::Orthographic::create(0, 1, 0, 1, -10,10), // left, right, bottom, top, near, far
      vsg::LookAt::create(vsg::dvec3(0.0, 0.0, 1.0),
                          vsg::dvec3(0.0, 0.0, 0.0),
                          vsg::dvec3(0.0, 1.0, 0.0)),
  
      vsg::ViewportState::create(window->extent2D()));

    auto view_overlay = vsg::View::create(static_camera);
    view_overlay->addChild(vsg::createHeadlight());
    vsg::ref_ptr<vsg::Node> quatNode;
    {
      auto w = window->extent2D().width;
      auto h = window->extent2D().height;
      vsg::GeometryInfo geomInfo;
      vsg::StateInfo stateInfo;
      geomInfo.color = vsg::vec4 {0.0f, 1.0f, 0.0f, 0.2f};
      geomInfo.transform = vsg::translate(0.5f, 0.5f, 0.0f)*vsg::scale(220.0f/w, 80.f/h, 1.0f)*vsg::translate(0.5f, 0.5f, 0.0f);
      
      quatNode = builder->createQuad(geomInfo, stateInfo);
      view_overlay->addChild(quatNode);

      geomInfo.color = vsg::vec4 {1.0f, 0.0f, 0.0f, 0.2f};
      geomInfo.transform = vsg::translate(0.51f, 0.51f, 0.0f)*vsg::scale(220.0f/w, 80.f/h, 1.0f)*vsg::translate(0.5f, 0.5f, 0.0f);
      quatNode = builder->createQuad(geomInfo, stateInfo);
      view_overlay->addChild(quatNode);

    }

    renderGraph->addChild(view_overlay);

    commandGraph->addChild(renderGraph);
    viewer->assignRecordAndSubmitTaskAndPresentation({commandGraph});

    viewer->compile();

[robertosfield]

Try setting:

 stateInfo.blending = true;

[dov]

Thanks @robertosfield ! That's what I was missing.