Need help with hit testing

I’m hoping someone can give me a few pointers for how to do hit testing in Urho3D. I have a scene with several BillboardSets and a few other nodes. I am trying to learn which billboard items are hit with either touch or the mouse.

One posting I read said you needed to raycast and said the Decals sample had an example. I am not able to figure out how to use that to accomplish hit testing.

Any words of advice?

Yes raycasting is what should help you. Not sure where your problem lies with it. In short you will need a check like this when you get a mouse click (or whenever you want to check)

        	unsigned int MASK = -1;//0xFFFFFFFF
        	Urho3D::Ray ray = camera->GetScreenRay(input->GetMousePosition().x_/float(window->GetSize().x_), input->GetMousePosition().y_/float(window->GetSize().y_));

        	PODVector<RayQueryResult> result;
        	RayOctreeQuery q(result, ray, RAY_AABB, M_INFINITY, DRAWABLE_GEOMETRY, MASK);
        	octree->RaycastSingle(q);

        	if(result.Size() > 0){
            	Drawable* selectedObject = result[0].drawable_;
			//we hit something!
			}

whereas window is your Urho3D::Graphics* window and the Urho3D::Octree* octree needs to be initialized, perhaps together with your camera like this

	octree = scene_->CreateComponent<Urho3D::Octree>();

The MASK property can be used to ignore certain objects but for most cases that is not necessary.

Thanks for the confirmation that this is the correct approach. I have it mostly working now.

I need to detect taps on the billboard items. It seems I need to use RAY_TRIANGLE rather than RAY_AABB for this to work. If using RAY_AABB, I get a hit if I tap anywhere in the billboardSet’s volume and the SubObject is always null. If I use RAY_TRIANGLE, I only get a hit when tapping on a billboard and SubObject will contain the index of the tapped billboard.

So I do have one additional problem. The billboards in this case can be somewhat small (they represent deep sky objects in our Galaxy). They are hard to tap when small. I was hoping I could use the Aabb option and just increase the size of the bounding box. That doesn’t seem like an option given what I said above.

I will either have to make the billboard larger and fill the periphery with transparent pixels, or I will need to do my own hot testing. Any thoughts on how to write my own RaycastSingle that detects a hit on a slightly larger area than the triangles?

You could clamp the texture UVs by creating a TextureName.xml in the same folder containing:

<address coord="u" mode="clamp" />
<address coord="v" mode="clamp" />

…and modify the U/V offsets in the material’s XML.

I think that should work.