Technical Deep Dive into the New Prefab System
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The document provides a technical overview of Unity's new prefab system, detailing its functionalities such as asset importing, prefab mode, and scripting tools. Key improvements include eliminating disconnected prefab instances and enhancing the editing experience within Unity's editor. The presentation targets developers seeking to understand the backend workings and changes related to prefab management in Unity.
![Editor Stages
43
• [ExecuteInEditMode]
• Will leave Prefab Mode
• [ExecuteAlways]](https://image.slidesharecdn.com/deepdiveintoprefabs-181123115545/85/Technical-Deep-Dive-into-the-New-Prefab-System-43-320.jpg)
![Editor Stages: [ExecuteAlways]
44
void Update()
{
// Rotate only in playmode
// We don't want this in edit mode nor in prefab mode
// as it would update the prefab asset
if (Application.IsPlaying(this))
{
Transform t = GetComponent<Transform>();
t.Rotate(rotationSpeed * Time.deltaTime, 0, 0);
}
++updateCount;
Debug.Log(string.Format("Updates {0}", updateCount));
}](https://image.slidesharecdn.com/deepdiveintoprefabs-181123115545/85/Technical-Deep-Dive-into-the-New-Prefab-System-44-320.jpg)
![46
I want to dynamically create an editing
environment for my prefab
using UnityEditor.Experimental.SceneManagement;
[InitializeOnLoad]
class CustomPrefabEnvironment
{
static CustomPrefabEnvironment()
{
PrefabStage.prefabStageOpened += OnPrefabStageOpened;
}
static void OnPrefabStageOpened(PrefabStage prefabStage)
{
…](https://image.slidesharecdn.com/deepdiveintoprefabs-181123115545/85/Technical-Deep-Dive-into-the-New-Prefab-System-46-320.jpg)
![51
How do I know if 2 GameObjects are part of the same Prefab Instance?
var firstHandle = PrefabUtility.GetPrefabInstanceHandle(Selection.gameObjects[0]);
var secondHandle = PrefabUtility.GetPrefabInstanceHandle(Selection.gameObjects[1]);
if (firstHandle == secondHandle)
Debug.Log("GameObject belongs to same instance");
else
Debug.Log("GameObject are not from the same instance");](https://image.slidesharecdn.com/deepdiveintoprefabs-181123115545/85/Technical-Deep-Dive-into-the-New-Prefab-System-51-320.jpg)
Technical Deep Dive into the New Prefab System
- 1. GenerativeArt–MadewithUnity 1 Technical Deep Dive into the New Prefab System Steen Lund Tech Lead, Unity Technologies @steenlund
- 2. Agenda 2 ● Prefab Assets, Instances and Content ● Prefab Importing ● Prefab Mode ● Unpacking ● Scripting and Tooling
- 3. Takeaway 3 ● Knowledge of how the backend works ● Changes to Unity’s handling of Prefabs assets ● Knowledge of Prefab tooling in the Editor
- 6. 6 Prefab Variants CatScene Cat (instance of Animal) Cat Animal Animal
- 8. Give some, take some 8 • No more disconnected Prefab instances • No more editing directly in the Project Browser
- 9. Prefab Assets, Instances and Content 9
- 11. 11 Make GameObject into Prefab instance
- 12. 12 Drag the GameObject to Project Browser
- 13. 13
- 14. What is a Prefab 14 Instance?
- 15. 15 PrefabInstance Handle Instance Leg Table More than you see with the naked eye
- 18. 18 Prefabs in Scene files Main Camera Directional Light Scene File PrefabInstance Handle Loaded Scene PrefabInstance Handle
- 19. What is a Prefab Asset? 19 Prefab File Table Leg
- 20. 20 Consider a Prefab Asset being a scene Prefab File Table Leg PrefabInstance Handle
- 22. 22 Prefab File in Assets Folder Prefab Importer Table Leg Prefab File in Library Folder Prefab Asset Handle Table Leg
- 23. 23 Prefab File in Assets Folder Prefab File in Library Folder Prefab Importer Table Leg PrefabInstance Handle Prefab Asset Handle Table Leg Vase PrefabInstance Handle
- 24. 24 Prefab Variant File in Assets Folder Prefab File in Library Folder Prefab Importer PrefabInstance Handle Prefab Asset Handle Vase PrefabInstance Handle
- 26. Corresponding Objects with Nesting 26 Table LegLeg Table VaseVase Vase TableScene Vase
- 27. Corresponding Objects with Variants 27 CatCat Animal CatScene Animal
- 28. 28 Dependency chain Prefab Importer Prefab Importer Inner Middle Outer
- 29. 29 Build size implications ● No change for Scene, have always been baked out at build time ● Resources and AssetBundles are affected AA A B C
- 30. 30 PrefabAsset Handle PrefabInstance Handle Asset in Library FolderPrefab Instance Table LegLeg Table VaseVase PrefabInstance Handle
- 31. Prefab Mode 31
- 32. 32 Edit Prefab in Prefab Mode
- 33. Prefab Mode Editing Prefab Asset content not Prefab instance GameObject icon not Prefab icon Saving not applying 33
- 34. 34 Prefab Asset Prefab instance Prefab contents in Prefab Mode automatic update apply open from instance open from asset save
- 35. Unpacking 35
- 36. 36 Prefabs can no longer be disconnected
- 37. 37
- 38. 38 Make Prefab instance into GameObject Unpack Prefab Contents (one layer)
- 39. 39 Make Prefab instance into GameObject Unpack Prefab Contents (one layer) Prefab Variant becomes its base
- 40. 40
- 42. Editor Stages 42 • Main Stage • Prefab Stage • ….
- 43. Editor Stages 43 • [ExecuteInEditMode] • Will leave Prefab Mode • [ExecuteAlways]
- 44. Editor Stages: [ExecuteAlways] 44 void Update() { // Rotate only in playmode // We don't want this in edit mode nor in prefab mode // as it would update the prefab asset if (Application.IsPlaying(this)) { Transform t = GetComponent<Transform>(); t.Rotate(rotationSpeed * Time.deltaTime, 0, 0); } ++updateCount; Debug.Log(string.Format("Updates {0}", updateCount)); }
- 45. Case: 45 I want to dynamically create an editing environment for my prefab
- 46. 46 I want to dynamically create an editing environment for my prefab using UnityEditor.Experimental.SceneManagement; [InitializeOnLoad] class CustomPrefabEnvironment { static CustomPrefabEnvironment() { PrefabStage.prefabStageOpened += OnPrefabStageOpened; } static void OnPrefabStageOpened(PrefabStage prefabStage) { …
- 47. Case: 47 Is my GameObject a Prefab (and what kind)?
- 48. Is my GameObject a Prefab (and what kind)? 48 PrefabInstanceStatus GetPrefabInstanceStatus(Object componentOrGameObject) PrefabAssetType GetPrefabAssetType(Object componentOrGameObject) bool IsAnyPrefabInstanceRoot(GameObject gameObject) bool IsOutermostPrefabInstanceRoot(GameObject gameObject) bool IsPartOfAnyPrefab([Object componentOrGameObject) bool IsPartOfImmutablePrefab(Object componentOrGameObject) bool IsPartOfPrefabThatCanBeAppliedTo(Object componentOrGameObject) bool IsPartOfPrefabAsset(Object componentOrGameObject) bool IsPartOfPrefabInstance(Object componentOrGameObject) bool IsPartOfNonAssetPrefabInstance(Object componentOrGameObject) bool IsPartOfRegularPrefab(Object componentOrGameObject) bool IsPartOfModelPrefab(Object componentOrGameObject) bool IsPartOfVariantPrefab(Object componentOrGameObject) bool IsDisconnectedFromPrefabAsset(Object componentOrGameObject) bool IsPrefabAssetMissing(Object instanceComponentOrGameObject)
- 49. Is my GameObject a Prefab (and what kind)? 49 if (PrefabUtility.IsPartOfPrefabInstance(go)) { var type = PrefabUtility.GetPrefabAssetType(go); Debug.Log(string.Format("GameObject is part of a Prefab Instance of type {0}" ,type)); } else { Debug.Log("Selected GameObject is not part of a Prefab Instance"); }
- 50. Case: 50 How do I know if 2 GameObjects are part of the same Prefab Instance?
- 51. 51 How do I know if 2 GameObjects are part of the same Prefab Instance? var firstHandle = PrefabUtility.GetPrefabInstanceHandle(Selection.gameObjects[0]); var secondHandle = PrefabUtility.GetPrefabInstanceHandle(Selection.gameObjects[1]); if (firstHandle == secondHandle) Debug.Log("GameObject belongs to same instance"); else Debug.Log("GameObject are not from the same instance");
- 52. Case: 52 I want to create a Prefab from script
- 53. I want to create a Prefab from script 53 var cube = GameObject.CreatePrimitive(PrimitiveType.Cube); // If you simply want the cube to be written as an asset but not turn into a prefab instance // use this method PrefabUtility.SaveAsPrefabAsset(cube, path); // This method will create a Prefab asset and make the GameObject an instance of the // new prefab asset PrefabUtility.SaveAsPrefabAssetAndConnect(cube, path, InteractionMode.AutomatedAction);
- 54. Case: 54 I want to create a Prefab Variant from script
- 55. I want to create a Prefab Variant from script 55 if (isAsset) { path = AssetDatabase.GetAssetPath(go); go = (GameObject)PrefabUtility.InstantiatePrefab(go); } else if (isInstance) { go = PrefabUtility.GetOutermostPrefabInstanceRoot(go); path = AssetDatabase.GetAssetPath(PrefabUtility.GetCorrespondingObjectFromSource(go)); } var prefabName = System.IO.Path.GetFileNameWithoutExtension(path); path = System.IO.Path.GetDirectoryName(path); PrefabUtility.SaveAsPrefabAsset(go, path + "/" + prefabName + " Variant.prefab");
- 56. Case: 56 I want to nest Prefabs from script
- 57. 57 I want to nest Prefabs from script var instanceA = (GameObject)PrefabUtility.InstantiatePrefab(goA); var instanceB = (GameObject)PrefabUtility.InstantiatePrefab(goB); instanceB.GetComponent<Transform>().parent = instanceA.GetComponent<Transform>(); PrefabUtility.ApplyPrefabInstance(instanceA, InteractionMode.AutomatedAction);
- 58. 58 I want to nest Prefabs from script var instanceB = (GameObject)PrefabUtility.InstantiatePrefab(goB); var root = PrefabUtility.LoadPrefabContents(path); instanceB.GetComponent<Transform>().parent = root.GetComponent<Transform>(); PrefabUtility.SaveAsPrefabAsset(root, path); PrefabUtility.UnloadPrefabContents(root);
- 59. Case: 59 I want to change a flag on multiple Prefabs assets
- 60. 60 I want to change a flag on multiple Prefabs assets // Load the content of the Prefab asset so we can modify it var assetRoot = PrefabUtility.LoadPrefabContents(path); GameObjectUtility.SetStaticEditorFlags(assetRoot, StaticEditorFlags.LightmapStatic); // Write the updated GameObject to the Prefab asset PrefabUtility.SaveAsPrefabAsset(assetRoot, path); // Clean up is important or we will leak scenes and // eventually run out of temporary scenes. PrefabUtility.UnloadPrefabContents(assetRoot);
- 61. Case: 61 I want to add assets to my prefab file AssetDatebase.AddObjectToAsset(newObject, asset);
- 62. Case: 62 Advanced: I modified a Library folder object, now I want to update the source asset
- 63. 63 Advanced: I modified a Library folder object, now I want to update the source asset string path = "Assets/Prefabs/A.prefab"; var goA = (GameObject)AssetDatabase.LoadMainAssetAtPath(path); GameObjectUtility.SetStaticEditorFlags(goA, ~GameObjectUtility.GetStaticEditorFlags(goA)); PrefabUtility.SavePrefabAsset(goA);
- 64. 64 Example code: https://github.com/Unity-Technologies/UniteLA2018Examples Scripting reference https://docs.unity3d.com/2018.3/Documentation/ScriptReference/PrefabUtility.html Prefabs landing page: https://unity3d.com/prefabs Nikoline Høgh: Oct. 24th 10 AM Prefab Workflow Improvements – An Introduction Location: Diamond 5
- 65. 65 Questions?