Intersect text with PolytopeIntersector or LineSegmentIntersector

[TP-David]

Pull Request Template

Description

Adds support for intersecting text using PolytopeIntersector or LineSegmentIntersector.

Adds computeBillboardMatrix method.

Type of change

• New feature (non-breaking change which adds functionality)

How Has This Been Tested?

Tested in vsgtext using the following eventHandler:

    class IntersectionHandler : public vsg::Inherit<vsg::Visitor, IntersectionHandler>
    {
    public:
        vsg::ref_ptr<vsg::Camera> camera;
        vsg::ref_ptr<vsg::Group> scenegraph;
        IntersectionHandler(
            vsg::ref_ptr<vsg::Camera> in_camera,
            vsg::ref_ptr<vsg::Group> in_scenegraph) :
            camera(in_camera),
            scenegraph(in_scenegraph)
        {
        }

        void apply(vsg::ButtonPressEvent& pointerEvent) override
        {
#if 1
            double size = 5.0;
            double xMin = static_cast<double>(pointerEvent.x) - size;
            double xMax = static_cast<double>(pointerEvent.x) + size;
            double yMin = static_cast<double>(pointerEvent.y) - size;
            double yMax = static_cast<double>(pointerEvent.y) + size;

            auto intersector = vsg::PolytopeIntersector::create(*camera, xMin, yMin, xMax, yMax);
#else
            auto intersector = vsg::LineSegmentIntersector::create(*camera, pointerEvent.x, pointerEvent.y);
#endif
            scenegraph->accept(*intersector);

            std::cout << "Hits: " << intersector->intersections.size() << std::endl;
        }

    };
    viewer->addEventHandler(IntersectionHandler::create(camera, scenegraph));

It prints 0 when clicking outside of text, and non-zero when clicking text (billboarded, CPU/GPU, different layouts).

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules