Mouse click a collision mesh

Questions & Answers
1

There is a lot of material on these forums about how to detect mouse presses on collision meshes, but I’ve been unable to adapt other user’s solutions for my own situation.

I dynamically create a game object at run time and give it a mesh (the meshes have come from an xml file and are just simple 2D flat polygons at y=0. There’s very little overlap (if any) between polygons).

So I have something like this when I parse in the xml file.

/
// Create the rendered mesh for the Game Object
//
Mesh mesh = new Mesh();
mesh.vertices = verticesTemp.ToArray();
mesh.colors = colors;
mesh.triangles = triangles;

//
// Dynamically create the GameObject and add the required components
//
GameObject gameObj = new GameObject(building.name);
gameObj.AddComponent("MeshFilter");
gameObj.AddComponent("MeshRenderer");
gameObj.AddComponent ("MouseHandler"); // Used for mouse events
gameObj.AddComponent("MeshCollider");
gameObj.renderer.material.shader = Shader.Find("PlainColorShader");
gameObj.GetComponent<MeshFilter>().mesh = mesh;

//
// Create a collision mesh (it's the same data as the rendered mesh)
//
Mesh collisionMesh = new Mesh();
collisionMesh.vertices = verticesTemp.ToArray();
collisionMesh.triangles = triangles;
			
MeshCollider meshCollider = gameObj.GetComponent<MeshCollider>();
meshCollider.sharedMesh = collisionMesh;

As a result, I have many GameObjects in the hierarchy and selecting each shows an attached Mesh Collider and Mouse Handler component (amongst other things)

When in Scene mode, I can see the green wireframe representing the collision mesh, but I can’t seem to be able to mouse click it using my MouseHander script/component that I’ve dynamically added to the GameObject.

I’ve tried casting rays upon mouse press inside the update() method…

void Update() {
   if (Input.GetMouseButtonDown(0)) {
      RaycastHit hit;
      if (Physics.Raycast(Camera.main.ScreenPointToRay(Input.mousePosition), out hit)) {
         Debug.Log("hit");
      }
   }	
}

…and I’ve also tried to use the OnMouseOver() method…

void OnMouseOver() {
   if (Input.GetMouseButtonDown(0)) {
    	Debug.Log("hit");
   }	
}

Does anyone have any ideas why this might not be working?

Thanks.

3

I suspect that the winding order of your triangles is incorrect: the vertices must be in clockwise order when you look at the triangle. I tested OnMouseDown with a single triangle mesh and it worked as expected. When reversing the triangle winding order, the mesh became invisible and could not be clicked. NOTE: I used the regular Diffuse shader in my tests - depending on the shader you’re using, your mesh may be rendered even if backfaced.

2

Your mesh normals are probably inverted. Raycasts/clicks will only be detected if the surface normals point towards the origin of the ray.

4

this doesn’t work for me either. How to change the normal for a mesh object (not created from scratch),What is vertexTemp here. I got the same problem, trying to fix the clockwise thing. Not clear how to fix it. Can you share you code a little more?