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+# Chapter 22: Integrating SpriteKit & SceneKit
+
+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 fwidth function
+
+fwidth() is equivalent to:
+
+```
+abs(dfdx(p)) + abs(dfdy(p))
+```
+
+The camera position is defined by the constant value in the fragment shader. It's not good because the camera position can be changed.
+
+In Shaders.metal, in shipFragment(), replace:
+
+```
+float3 v = normalize(float3(0, 0, 10)); // camera position
+```
+
+With:
+
+```
+float3 v = normalize(cameraPosition);
+```
+
+Add the float3 as a parameter to the fragment function:
+
+```
+constant float3 &cameraPosition
+```
+
+In GameViewController.swift, in the conditional block where you set up the material, add this:
+
+```
+let cameraPosition = cameraNode.position
+material.setValue(cameraPosition, forKey: "cameraPosition")
+```
+
+step() generates a step function by comparing x to edge:
+
+![](./step-function.png)
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@@ -35,6 +35,7 @@ You can see color images in this book at [here](https://www.raywenderlich.com/bo
  * [Chapter 19: Advanced Shadows](https://github.com/daemyung/metal-by-tutorials/tree/main/19-shadows)
  * [Chapter 20: Advanced Lighting](https://github.com/daemyung/metal-by-tutorials/tree/main/20-advanced-lighting)
  * [Chapter 21: Metal Performance Shaders](https://github.com/daemyung/metal-by-tutorials/tree/main/21-metal-performance-shaders)
+ * [Chapter 22: Integrating SpirteKit & SceneKit](https://github.com/daemyung/metal-by-tutorials/tree/main/22-integrating-spritekit-scenekit)
 
 ## Copyright