From 273aa3e0ec31a778ca69ce0f85f3a92bf6919ac0 Mon Sep 17 00:00:00 2001
From: daemyung jang <dm86.jang@gmail.com>
Date: Wed, 16 Feb 2022 14:34:17 +0900
Subject: [PATCH] Summerize Chapter 9: The Scene Graph

---
 09-scene-graph/README.md | 39 +++++++++++++++++++++++++++++++++++++++
 README.md                |  1 +
 2 files changed, 40 insertions(+)
 create mode 100644 09-scene-graph/README.md

diff --git a/09-scene-graph/README.md b/09-scene-graph/README.md
new file mode 100644
index 0000000..7c4550e
--- /dev/null
+++ b/09-scene-graph/README.md
@@ -0,0 +1,39 @@
+# Chapter 9: The Scene Graph
+
+As I read this book, I summarize what I think is wrong. If you think my comments are wrong then please let me know. We can dicuss more and update your opinion.
+
+## The scene graph
+
+* You can also remove the light when you cleanup your code. In `Scene.swift`, add this:
+
+```
+var lighting = Lighting()
+```
+
+In `Renderer.swift`, in `func draw(in view: MTKView)`, replace:
+
+```
+var lights = lighting.lights
+```
+
+With:
+
+```
+var lights = scene.lighting.lights
+```
+
+* If you remove a camera in 'Renderer', you need to update `override func scrollWheel(with event: NSEvent)` in `ViewControllerExtension.swift`, replace:
+
+```
+override func scrollWheel(with event: NSEvent) {
+  renderer?.camera.zoom(delta: Float(event.deltaY))
+}
+```
+
+With:
+
+```
+override func scrollWheel(with event: NSEvent) {
+  renderer?.scene?.camera.zoom(delta: Float(event.deltaY))
+}
+```
diff --git a/README.md b/README.md
index f62a527..28a8cf1 100644
--- a/README.md
+++ b/README.md
@@ -23,6 +23,7 @@ You can see color images in this book at [here](https://www.raywenderlich.com/bo
  * [Chapter 5: Lighting Fundamentals](https://github.com/daemyung/MetalByTutorials/tree/main/05-lighting-fundamentals)
  * [Chapter 6: Textures](https://github.com/daemyung/MetalByTutorials/tree/main/06-textures)
  * [Chapter 8: Character Animation](https://github.com/daemyung/MetalByTutorials/tree/main/08-character-animation)
+ * [Chapter 9: The Scene Graph](https://github.com/daemyung/MetalByTutorials/tree/main/09-scene-graph)
 
 ## Copyright