Model rotation

[GaussGun3000]

I had following function to place a model at coordinates (had to change it for recent Result refactoring, but nothing else):

inline Result<IOResponse, Failure> placeModelAt(
    Application& app,
    const glm::dvec3& geoPt,
    const std::string& modelUri,
    double scale = 1.0,
    double zOffset = 0.0)
{
    entt::entity entity = entt::null;
    using IOResult = Result<IOResponse, Failure>;

    // 1) Read
    auto io = URI(modelUri).read(app.io());   // IOResult
    if (io.failed()) return io;

    // 2) Parse
    auto options = vsg::Options::create(*app.vsgcontext->readerWriterOptions);
    auto ext = std::filesystem::path(URI(modelUri).full()).extension();
    options->extensionHint = ext.empty()
        ? std::filesystem::path(io.value().content.type)
        : ext;

    std::stringstream in(io.value().content.data);
    auto node = vsg::read_cast<vsg::Node>(in, options);
    if (!node) return IOResult(Failure{"Failed to parse model"});

    // 3) Create entity
    auto [lk, registry] = app.registry.write();
    entity = registry.create();
    //  Host the VSG node
    auto& modelComp = registry.emplace<NodeGraph>(entity);
    modelComp.node  = node;
    //  Place & scale it geodetically, applying zOffset
    auto& xform = registry.emplace<Transform>(entity);
    xform.position    = GeoPoint(
                SRS::WGS84,
                geoPt.x,
                geoPt.y,
                geoPt.z + zOffset
                );
    xform.localMatrix = glm::scale(
                glm::dmat4(1.0),
                glm::dvec3(scale)
                );
    xform.dirty();


    return io; // success
}

It used to perfectly align model to earth surface. But now I get this:

I know I can build an "up" vector and align model to it, but I want to know if there's an easier way to do that

[gwaldron]

You probably need to set

xform.topocentric = true;

This sets whether the coordinate system at the point is a local tangent plane to the earth (topocentric=true) or just a global translation (false).

The default for this changed at some point; I suspect that is the issue. Hope this helps.

[GaussGun3000]

Thanks, that's exactly what I needed.
A little side question: do you find these kind of questions useful to project (to make Q&A base for googling and AI tools), or what do you think about them?

[gwaldron]

Yes, very useful! Every Q&A adds to the knowledge base and gives us a better idea of what needs more or better documenting. Thanks!