How to draw using inbuilt primitives?

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#1

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
#2

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
#3

Or you can use DebugDraw utilities for that…

#4

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!

#5

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.