How can I create an object at the mouse point in scene view by clicking not dragging the object? - unity3d

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.