How can I create an object at the mouse point in scene view by clicking not dragging the object?

Question

Generally, most objects are placed in the scene view by dragging or something. I want to right click the mouse (without dragging an object) to create an object in the scene view. I know this would require some editor coding but I’m not sure how to go about it.

UPDATE

After giving it some thought I realised that using a MenuItem would be quite appropriate for me. Here is my code below:

SLMenuItems:

public class SLMenuItems : MonoBehaviour {

public bool canClickSceneViewToCreatePath = false;

void Start()
{

}

[MenuItem("Component/Create Custom Object")]
static void CreateObject()  {
   Debug.Log("menu item selected");
    canClickSceneViewToCreatePath = true;
} 
}

SLMenuItemsEditor:

    [CustomEditor(typeof(SLMenuItems))]
public class SLMenuItemsEditor : Editor {
    SLMenuItems slMenuItems;


    void OnEnable()
    {
        slMenuItems = (SLMenuItems)target;

    }


    void OnSceneGUI()
        {
            if (slMenuItems.canClickSceneViewToCreatePath)  {
                Vector3 pointsPos = HandleUtility.GUIPointToWorldRay(Event.current.mousePosition).origin;

                if (Event.current.type == EventType.MouseDown && Event.current.button == 0)
                {

                    // create object here at pointsPos

                    slMenuItems.canClickSceneViewToCreatePath = false;
                }
            }

        }
    }

I keep getting the following error:

Assets/SLMenuItems.cs(23,9): error CS0120: An object reference is required to access non-static member `SLMenuItems.canClickSceneViewToCreatePath'

pointing to the line:

canClickSceneViewToCreatePath = true;

in SLMenuItems.

Answer 1

Your CreateObject method is static but your canClickSceneViewToCreatePath value is not.

It has nothing to do with the editor script but with your class SlMenuItems itself.

A static method is not instanced or with other words it is kind of shared between all instances of that component type while the non-static value might be different for each component.

So how should a static method - which is the same for all instances - "know", which of the instances values it should access?

So either make the method non-static or the variable static. Depending on what your further need is.

Since the MenuItem needs a static method make the variable static as well.

---

I would suggest you make that class not inherit from MonoBehaviour at all since it doesn't have any behaviour for a GameObject. It only brings some editor features so rather make it a static class that can "live" in the Assets without needing to be instanced.

Than you can use SceneView.onSceneGUIDelegate to register a callback for OnSceneGUI without implementing an editor script for that:

private static GameObject lastCreated;

private static bool isCreating;

public static class SLMenuItems
{   
    [MenuItem("Component/Create Custom Object")]
    private static void CreateObject() 
    {
        Debug.Log("menu item selected");

        isCreating = true;
        lastCreated = null;

        // Add a callback for SceneView update
        SceneView.onSceneGUIDelegate -= UpdateSceneView;
        SceneView.onSceneGUIDelegate += UpdateSceneView;
    }

    private static void UpdateSceneView(SceneView sceneView)
    {
        if(lastCreated)
        {
            // Keep lastCreated focused
            Selection.activeGameObject = lastCreated;
        }

        if(isCreating)
        {  
            if (Event.current.type == EventType.MouseDown && Event.current.button == 0)
            {
                Vector3 pointsPos = HandleUtility.GUIPointToWorldRay(Event.current.mousePosition).origin;

                //Todo create object here at pointsPos
                lastCreated = Instantiate(somePrefab);

                // Avoid the current event being propagated
                // I'm not sure which of both works better here
                Event.current.Use();
                Event.current = null;

                // Keep the created object in focus
                Selection.activeGameObject = lastCreated;

                // exit creation mode
                isCreating = false;
            }
        } 
        else
        {
            // Skip if event is Layout or Repaint
            if(e.type == EventType.Layout || e.type == EventType.Repaint)
            {
                Selection.activeGameObject = lastCreated;
                return;
            }

            // Prevent Propagation
            Event.current.Use();
            Event.current = null;
            Selection.activeGameObject = lastCreated;
            lastCreated = null;

            // Remove the callback
            SceneView.onSceneGUIDelegate -= UpdateSceneView;
        }      
    }
}

---

But I suggest you change your questions title since this is actually not the solution to the "task" you describe before.