UnityEditor.HandleUtility.RaySnap C# (CSharp) Method

        public static object RaySnap(Ray ray)
        {
            RaycastHit[] hitArray = Physics.RaycastAll(ray, float.PositiveInfinity, Camera.current.cullingMask);
            float positiveInfinity = float.PositiveInfinity;
            int index = -1;
            if (ignoreRaySnapObjects != null)
            {
                for (int i = 0; i < hitArray.Length; i++)
                {
                    if (hitArray[i].collider.isTrigger || (hitArray[i].distance >= positiveInfinity))
                    {
                        continue;
                    }
                    bool flag = false;
                    for (int j = 0; j < ignoreRaySnapObjects.Length; j++)
                    {
                        if (hitArray[i].transform == ignoreRaySnapObjects[j])
                        {
                            flag = true;
                            break;
                        }
                    }
                    if (!flag)
                    {
                        positiveInfinity = hitArray[i].distance;
                        index = i;
                    }
                }
            }
            else
            {
                for (int k = 0; k < hitArray.Length; k++)
                {
                    if (hitArray[k].distance < positiveInfinity)
                    {
                        positiveInfinity = hitArray[k].distance;
                        index = k;
                    }
                }
            }
            if (index >= 0)
            {
                return hitArray[index];
            }
            return null;
        }

        public void OnSceneDrag(SceneView sceneView)
        {
            GameObject go = target as GameObject;

            if (!PrefabUtility.IsPartOfPrefabAsset(go))
            {
                return;
            }

            var prefabAssetRoot = go.transform.root.gameObject;

            Event evt = Event.current;

            switch (evt.type)
            {
            case EventType.DragUpdated:

                Scene destinationScene = sceneView.customScene.IsValid() ? sceneView.customScene : SceneManager.GetActiveScene();
                if (dragObject == null)
                {
                    dragObject           = (GameObject)PrefabUtility.InstantiatePrefab(prefabAssetRoot, destinationScene);
                    dragObject.hideFlags = HideFlags.HideInHierarchy;
                    dragObject.name      = go.name;
                }

                if (HandleUtility.ignoreRaySnapObjects == null)
                {
                    HandleUtility.ignoreRaySnapObjects = dragObject.GetComponentsInChildren <Transform>();
                }

                DragAndDrop.visualMode = DragAndDropVisualMode.Copy;
                object hit = HandleUtility.RaySnap(HandleUtility.GUIPointToWorldRay(evt.mousePosition));

                if (hit != null)
                {
                    RaycastHit rh     = (RaycastHit)hit;
                    float      offset = 0;
                    if (Tools.pivotMode == PivotMode.Center)
                    {
                        float geomOffset = HandleUtility.CalcRayPlaceOffset(HandleUtility.ignoreRaySnapObjects, rh.normal);
                        if (geomOffset != Mathf.Infinity)
                        {
                            offset = Vector3.Dot(dragObject.transform.position, rh.normal) - geomOffset;
                        }
                    }
                    dragObject.transform.position = Matrix4x4.identity.MultiplyPoint(rh.point + (rh.normal * offset));
                }
                else
                {
                    dragObject.transform.position = HandleUtility.GUIPointToWorldRay(evt.mousePosition).GetPoint(10);
                }

                // Use prefabs original z position when in 2D mode
                if (sceneView.in2DMode)
                {
                    Vector3 dragPosition = dragObject.transform.position;
                    dragPosition.z = prefabAssetRoot.transform.position.z;
                    dragObject.transform.position = dragPosition;
                }

                evt.Use();
                break;

            case EventType.DragPerform:

                var stage = StageNavigationManager.instance.currentItem;
                if (stage.isPrefabStage)
                {
                    var prefabAssetThatIsAddedTo = AssetDatabase.LoadMainAssetAtPath(stage.prefabAssetPath);
                    if (PrefabUtility.CheckIfAddingPrefabWouldResultInCyclicNesting(prefabAssetThatIsAddedTo, go))
                    {
                        PrefabUtility.ShowCyclicNestingWarningDialog();
                        return;
                    }
                }

                Transform parent = sceneView.customParentForDraggedObjects;

                string uniqueName = GameObjectUtility.GetUniqueNameForSibling(parent, dragObject.name);
                if (parent != null)
                {
                    dragObject.transform.parent = parent;
                }
                dragObject.hideFlags = 0;
                Undo.RegisterCreatedObjectUndo(dragObject, "Place " + dragObject.name);
                EditorUtility.SetDirty(dragObject);
                DragAndDrop.AcceptDrag();
                Selection.activeObject             = dragObject;
                HandleUtility.ignoreRaySnapObjects = null;
                if (SceneView.mouseOverWindow != null)
                {
                    SceneView.mouseOverWindow.Focus();
                }
                dragObject.name = uniqueName;
                dragObject      = null;
                evt.Use();
                break;

            case EventType.DragExited:
                if (dragObject)
                {
                    UnityObject.DestroyImmediate(dragObject, false);
                    HandleUtility.ignoreRaySnapObjects = null;
                    dragObject = null;
                    evt.Use();
                }
                break;
            }
        }