How to draw using inbuilt primitives?

Hello everyone,

I have recently started developing with Urho3d and am amazed at how powerful yet simple it is to use. After a quick test, I have come to a point where I need to draw a path (line/spline/curve), but I cannot find any good resource to do so.

Upon further investigation, I came across the folder - LinePrimitives under CoreData.Models which contains some model files named Basis.mdl and CubicBezier.mdl etc. I’m hoping that these will somehow be used to draw a path.

Can someone point me in the right direction on how to use these ?

Thanks!

1 Like

I’ve used them in the following manner to create a grid:

    Node* gridNode_ = scene->CreateChild("Grid");
    gridNode_->SetPosition(Vector3::ZERO);

    int gridSize = 32;
    float blockScale = 1.0f; // size of each cell in the grid.

    // Use instancing to draw the lines to display tiles.
    Node* lineTileGroupNode = gridNode_->CreateChild("GridLineTileGroup");
    StaticModelGroup* lineTileGroup = lineTileGroupNode->CreateComponent<StaticModelGroup>();
    lineTileGroup->SetModel(cache->GetResource<Model>("Models/LinePrimitives/UnitX.mdl"));

    // Set your material
    lineTileGroup->SetMaterial(mat);

    // Iterate creating both the vertical and horizontal lines.
    for (int i = 0; i <= gridSize; i++) {
        Node* hNode = gridNode_->CreateChild("GridTileLineH");
        hNode->SetPosition(Vector3(0, 0, i * blockScale));
        hNode->SetScale(Vector3(blockScale * gridSize, 0.0f, 0.0f));
        lineTileGroup->AddInstanceNode(hNode);

        // You could use the UnitY.mdl model, or just rotate the one you already have.
        Node* vNode = gridNode_->CreateChild(fmt::format("GridTileLineV", i).c_str());
        Quaternion rot = Quaternion::IDENTITY;
        rot.FromEulerAngles(0.0f, -90.0f, 0.0f);
        vNode->SetPosition(Vector3(i * blockScale, 0, 0));
        vNode->SetRotation(rot);
        vNode->SetScale(Vector3(blockScale * gridSize, 0.0f, 0.0f));
        lineTileGroup->AddInstanceNode(tNode);
    }
3 Likes

Or you can use DebugDraw utilities for that…

Thanks for the code Victor. However, I could not get the bezier models (CubicBezier,LinearBezier, QuadraticBezier) to work. The others did work though; but that’s not what I am looking for.

@johnnycable : Thanks for the tip. I tried using the debug draw to draw lines , circles and quads, but the renderings are really basic and primitive looking and good for exactly that - debugging.

What I have in mind is more on the lines of -

via GIPHY

or

via GIPHY

Any help would be greatly appreciated! Thanks!

I’ve searched for that too. None found. You have to create your own line drawing with noise functions (drawing geometry) and coat them fluo design. You could use st like @Lumak Basic material effects for rendering.

UrhoSharp ported Skia library into for that.