Placing models on click, detecting collision


One of the challenges i’m facing when migrating away from Unity is re-implementing this system:!/content/45147

Basically, it allows me to place models at runtime, based on a grid. I’ve started a small proof of concept, but i’m having a hard time:

  • Snapping models together
  • Snapping models to the terrain. This is, by far, the hardest. What’s the most effective way of checking how i can place a model on a terrain?


To specifically get the height on a terrain, you can use the GetHeight() method:

If you wanted a more generic way to query different geometry snapping locations, you could use OctreeQuery:

Usually these kinds of modular setups require some basic model preparation – if you set up the origin of the model to be at the bottom and have the model contained entirely in the positive axis, then placing them is a lot more managable.


Thank you. Also, for snapping on sibiling model edges, any tips? :slight_smile:


My first attempt would be to use the bounding box to determine the approximate size of the model and space them based on that. I haven’t played with the asset you linked to, so I’m not aware of any advanced behaviours they might have used.


Is there any further info on this subject? I’m also struggling to create something like this:

In Urho.


Anyone, please? I keep having problems with geo. An example would be great. :frowning:


My suggestion would be to not do it based in geometry. Use prefabs instead of just models and include snap-points in them - up to you how to do this, but I would suggest either categorical ones - window here, door here, floor/wall/door here, or size based ones. The snap points can just be other nodes in the prefab, and just copy the world position and rotation from them when adding a new node. Another suggestion is looking into how snapping weapons to hands and such is usually done.

Alternatively, it you have only regularly sized components (like Minecraft), you can define a grid system whenever you add a component, unless it meets some criteria to add it to the grid of a previous one.

If you’re just looking into how to do it statically (not as part of the game), I would look into how to do it in Blender, etc. and then just import the scene.


Are prefabs possible in Urho3D? Are they just serialized scenes?