Archive 17/01/2023.

Get world point where spotlight hits

nergal

Is there a way to get the point in the world where a spotlight (LIGHT_SPOT) hits an object? And if not hitting an object, I would like to have the point where the spotlight ends when I’ve defined “SetRange(x)” for the light.

If so, it would also be good if I could get the actual object being hit.

Modanung

You’d probably want to use an octree raycast, as happens in several samples:

github.com

urho3d/Urho3D/blob/master/Source/Samples/08_Decals/Decals.cpp#L295


// Check the cursor is visible and there is no UI element in front of the cursor

if (!ui->GetCursor()->IsVisible() || ui->GetElementAt(pos, true))

    return false;



Graphics* graphics = GetSubsystem<Graphics>();

Camera* camera = cameraNode_->GetComponent<Camera>();

Ray cameraRay = camera->GetScreenRay((float)pos.x_ / graphics->GetWidth(), (float)pos.y_ / graphics->GetHeight());

// Pick only geometry objects, not eg. zones or lights, only get the first (closest) hit

PODVector<RayQueryResult> results;

RayOctreeQuery query(results, cameraRay, RAY_TRIANGLE, maxDistance, DRAWABLE_GEOMETRY);

scene_->GetComponent<Octree>()->RaycastSingle(query);

if (results.Size())

{

    RayQueryResult& result = results[0];

    hitPos = result.position_;

    hitDrawable = result.drawable_;

    return true;

}



return false;

}

Instead of the cameraRay you would have a ray starting at the position of the spotlight with a maxDistance equal to the light’s range.
Once you have a RayQueryResult you’ve got a Node which you can check for tags or derived components as well as the position where the ray hit.

nergal

Thanks! Worked like a charm!