Errata for Metal by Tutorials 3rd Edition

đź“š Official Books Metal by Tutorials
1

Creating this topic to catch any typos and bugs in the 3rd Edition of Metal by Tutorials.

3

I found a typo on the PDF page 27,
Who This Book Is For?
We recommend the Swift Apprentice book, available in our catlagoue:

Should be catalogue.

Kind regards
Fernando

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4

Thank you for the update, I was just doing some reading over the selection I’d buffer, and noticed that there is a multiple of two which is assuming the screen draw scale is 2 this does change depending on the device and screen. Pg 252 “* 2”

I would suggest you use contentScaleFactor.native or UIScreen.main.scale. It depends on how you are accessing the screen position data.

Hope that helps, as I got caught out by this when writing my idBuffer and testing on different devices.

Cheers Si

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5

The ToC bookmarks in both the PDF and ePub say “Chapter 21: Imaged-based lighting”. Should be “Image-based lighting”.

In the ePub the chapter header itself is spelled correctly, while in the PDF it still says “Imaged-based”.

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6

@rumor - Yes! That’s a lesson in not using magic numbers.

To correct this, I think an extra parameter on params would be useful.

➤ In Common.h, add this property to params:

uint scaleFactor;

➤ In Renderer.swift, add this to the end of init(metalView:options:):

#if os(macOS)
  params.scaleFactor = uint(NSScreen.main?.backingScaleFactor ?? 1)
#elseif os(iOS)
  params.scaleFactor = uint(UIScreen.main.scale)
#else
  params.scaleFactor = 1
#endif

➤ In PBR.metal, replace:

uint2 coord = uint2(params.touchX * 2, params.touchY * 2);

with:

uint2 coord = uint2(
  params.touchX * params.scaleFactor,
  params.touchY * params.scaleFactor);

Thank you :slight_smile: .

7

Chapter 22

Final code:

I was wondering about this line:

float2 rippleY = float2(-uv.x, uv.y) + timer

Is it the intention here to add timer to both xy components? (I’m assuming that is what adding a scalar float to a vector float does.)

Or should this line be:

float2 rippleY = float2(-uv.x, uv.y + timer);

Since timer is only added to the x component for rippleX:

float2 rippleX = float2(uv.x + timer, uv.y);
8

I can’t say what @mhorga’s original intention was, but the nice thing about fragment shaders is that when you’re not creating a physically exact reproduction, you can create the effect you want for your render.

I tried both options, and I prefer the original code as written. When timer is applied the same to x and y, I find that the ripples are too straight. But you can go with whatever you think looks best.

9

I believe I’ve found an error at the beginning of chapter 4, when creating the vertices to pass along as a raw bytes buffer to the vertex shader.

See my post here: Chapter 4 (Third Edition) shader validation error :slight_smile:

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10

Perhaps another possible bug, but still in chapter 4, under the Adding Another Vertex Attribute section, the snippet for creating the color buffer is the following:

guard let colorBuffer = device.makeBuffer(
  bytes: &colors,
  length: MemoryLayout<simd_float3>.stride * indices.count,
  options: []) else {
    fatalError("Unable to create quad color buffer")
  }
self.colorBuffer = colorBuffer

I believe the length is incorrect. It should be:

MemoryLayout<simd_float3>.stride * colors.count

Otherwise we’re multiplying by 6 instead of 4, which is the amount of SIMD Float3 elements in the array!

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11

Yes, you’re absolutely right!

colors.count is correct, not indices.count :woman_facepalming:

12

In chapter 7 right before the checker board graphic please revisit step 3. I believe you misinterpreted the result of the step function.

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14

Hi, for chapter 7, I think the MemoryLayout should take Params as input instead of Uniforms

renderEncoder.setFragmentBytes(
  &params,
  length: MemoryLayout<Uniforms>.stride,  // HERE, should it be <Params>?
  index: 12)
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15

Good catch - thanks! It’s allocating too much memory using Uniforms as the stride.

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16

Hi, for chapter 8, for the picture that denoted as “UV coordinates”, I think the coordinates whose y value are 0.15 should swap with the ones whose y values are 0.34.

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17

It certainly looks like it! :clap:- that’s made it through three editions!

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18

Chapter 6: Coordinate Spaces

The Starter Project

image
image1455Ă—168 66.5 KB

I think it should be MTLVertexDescriptor right ?

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19

Absolutely yes! Thank you very much for pointing this out.

20

Enjoying the book. I noticed in chapter 11 on normal maps, page 296 the first section ends: “and that’s the power of normal apps” and I think you intended that final word to be maps.

Thanks!!

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21

[Chapter 10 Lighting Fundamentals]

In Ambient Reflection part, I noticed the intensity attribute is not there as it says in the book description

image
image871Ă—365 46.6 KB

Common.h:

typedef struct {
  LightType type;
  vector_float3 position;
  vector_float3 color;
  vector_float3 specularColor;
  float radius;
  vector_float3 attenuation;
  float coneAngle;
  vector_float3 coneDirection;
  float coneAttenuation;
  float intensity;                                 // <-- insert here
} Light;

SceneLighting.swift:

struct Lighting {
  static func buildDefaultLight() -> Light {
    var light = Light()
    light.position = [0, 0, 0]
    light.color = [1, 1, 1]
    light.specularColor = [0.6, 0.6, 0.6]
    light.attenuation = [1, 0, 0]
    light.type = Sun
    light.intensity = 0.1                          // <-- insert here
    return light
  }

  let ambientLight: Light = {
    var light = Self.buildDefaultLight()
    light.color = [0.05, 0.1, 0]
    light.intensity = 0.5                         // <-- change property here
    light.type = Ambient
    return light
  }()

Lighting.metal:

float3 phongLighting(...) {
  // code
  case Ambient: {
     ambientColor += light.color * light.intensity; // <-- that right ?
     break;
  }
  // code
}
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