mmp/pbr-book-website

Physically Based Rendering, Online Edition

This repository contains the content for the online edition of the Physically Based Rendering book.

We are making the repository available in order to make it easier to read the book offline. For example, executing python3 -m http.server 8000 in the top-level directory makes it possible to read the book in a web browser pointed at localhost:8000.

The online version of the book (including the contents of this git repository) is made available under a CC BY-ND-NC 4.0 license.

pbr-book-website's Issues

3rd ed - Incorrect link to Lux Renderer

In 1.3.1, the link to Lux Renderer is incorrect. It should be https://luxcorerender.org/, not luxrenderer.net

The google search box in the 4th edition online book shows results from the 3rd edition

The google search box at the upper-right corner of the 4th edition of the online book seems to always show results from the 3rd edition.

Could I translate this book into Chinese?

Hi, thank you for your sharing. It pretty good. Could I translate this book into Chinese? （uncommercial）

Definition of "a" missing in Fresnel conductor equations?

Hi,

I was looking at the equations for Fresnel reflectance between a dielectric and a conductor in Eq. 8.3, but cannot find the definition for the term a in the text, which would be needed to implement them.
Only a^2+b^2 is given, but a also appears on its own, so I'm wondering if its definition should be added there, e.g.

$a = \sqrt{\frac{1}{2}\left(\sqrt{(\eta^2-k^2-\sin^2\theta)^2+4\eta^2k^2}+\eta^2-k^2-\sin^2\theta\right)}$

(as in Shirley's Thesis, Eq. 2.6, assuming eta_i = 1)

Thanks for your great work and best regards,
Lukas

3.8.2 Spherical Polygons, Equation 3.6

Formula 3.6 for calculating the area of a spherical triangle: Link

I might be misunderstanding but this formula does not make sense to me. Is this a typo? If it is correct, it would maybe help to add some context for deriving the formula (maybe in the Appendix).

Following from the code, the numerator should be dot(a, cross(b, c)).

Is there a pdf version of this book?

Equation Error in 13.8 - Careful Sample Placement?

Is there a $^2$ missing in the 7th equation block in 13.8 Careful Sample Placement?

Here's my calculation:

Furthermore, had there not been a sqr term, the latter part might always be 0:

errata: rejection sampling a unit disk

Caption of figure 13.6: Rejection Sampling a Circle. One approach to finding uniform points in the unit circle is to sample uniform random points in the unit square and reject all that lie outside the circle (red points). The remaining points will be uniformly distributed within the circle.
The circumscribed square is 2x2.

The title of the example where that figure is located is: Example: Rejection Sampling a Unit Circle
Changing to unit disk would make it clearer, or even to points inside a unit circle to go with the idea of the inside/outside test.

Need help with 2.2.1

The way I understand stratified sampling is this:

so naturally

but what is this fractional volume doing here?

and I don't understand these two at all, each stratum is an integral over lambda i, shouldn't the integrand be f(x) itself?

Typo on section 2.2.2 Importance Sampling

Is figure 2.2 in section 2.2 wrong?

It should look like this, right?

Website images don't render without GPU.

All that is seen is white image and it also triggers a black screen, not the best experience.

Missing Participating Media Type

Hello!

I was looking through the documentation for participating media for PBRTv3 and PBRTv4 the other day, and noticed that the second scene description example looks wrong:

MakeNamedMedium "mymedium" "homogeneous" "rgb sigma_s" [100 100 100]
MediumInterface "" "mymedium"

Looking at the PBRT code itself, I believe there's a missing "string type" before the "homogeneous", for both the v3 and v4 documentation.

Link references:
V3: https://www.pbrt.org/fileformat-v3#media-world
V4: https://www.pbrt.org/fileformat-v4#media-world

About the sections removed from the 3rd edition

Hi~ I'm very excited about the release of the 4th edtion! Many thanks to all of the authors and contributors. I'm sure it's an excellent book.

I note that some sections from the 3rd edtion are removed after updating. For example, in Chapter 1~8:

• Animating Transformations
• Subdivision Surfaces
• Kd-Tree Accelerator
• Realistic Cameras
• (0, 2)-Sequence Sampler
• Maximized Minimal Distance Sampler

Are there any special reasons for removing them?

Additional online edition content missing from the online edition

In the 4th edition, there are references to sections that are available in the online edition of the book https://www.pbr-book.org/4ed/Introduction/How_to_Proceed_through_This_Book#TheOnlineEdition. These sections don't appear to be listed in the online edition however. Are there any substantial differences from the corresponding sections of the thrid edition?

PBRTv3 Scenes Are Unavailable

It seems like the example scenes for PBRTv3 are unavailable (https://pbrt.org/scenes-v3) due to a HTTP Strict Transport Security (HSTS) violation (currently, via the URL https://pub-49ca6a23a58a46ef9cf5a5b34413a7ba.r2.dev/pbrt-v3-scenes.tar.gz)

Maybe there are some typos

pbr-book-website/3ed-2018/Shapes/Other_Quadrics.html

Line 1355 in 02b496a

<title id="MathJax-SVG-1-Title">x squared plus y squared minus z squared equals negative 1 comma</title>

I really like this amazing work and thank you for your sharing this book!

I have a problem with the implicit form of the hyperboloid:
It is x^2+y^2-z^2=-1, which means that it is a two-sheet hyperboloid.
But the parametric form shows that it is generated by a rotating line passing through points (x1,y1,z1) and (x2,y2,z2),
which should be a one-sheet hyperboloid.
Maybe the implicit form of the hyperboloid should be changed to x^2+y^2-z^2=1 for consistency.

Reference:https://en.wikipedia.org/wiki/Hyperboloid

Should this be "area density" instead of "solid angle density" in the book?

In PBR-book chapter 16.3, when the book is introducing the function PdfLightOrigin, it says:

<<Return solid angle density for non-infinite light sources>>

The returned value is directly assigned to some_vertex.pdfFwd. Since pdfFwd field in the vertex should store density defined in area measure for MIS uses. Some implementation of Pdf_Le (which returns pdf_pos and is directly used in PdfLightOrigin) also indicate this, for example, diffusive area source returns pdf_pos = 1 / Area().
Upon first reading this, I directly implemented PdfLightOrigin to return solid angle density for all light sources, but latter I think it doesn't make any sense... Could this be a mistake? Like, it were copy-pasted from the introduction of infinite light source procedure above?

Typo on https://pbrt.org

It says "The full contents of the third edition are now freely available online." on https://pbrt.org but the link points to the fourth edition.

Code on the website that will lead to confusion

In chapter 15.2 - Sampling Volume Scattering, for H-G phase function sampling:

<<Compute  for Henyey–Greenstein sample>>= 
Float cosTheta;
if (std::abs(g) < 1e-3)
    cosTheta = 1 - 2 * u[0];
else {
    Float sqrTerm = (1 - g * g) /
                    (1 - g + 2 * g * u[0]);
    cosTheta = (1 + g * g - sqrTerm * sqrTerm) / (2 * g);                         // HERE
}

There should be a negative sign in front of cosTheta RHS.

The code block is not consistent with , and is not consistent with

• PhaseHG function definition: Float denom = 1 + g * g + 2 * g * cosTheta;, if no minus sign given, denom should be 1 + g * g - 2 * g * cosTheta. According to the ray direction convention in PBRT-v3, all 'incident ray' points outwards, therefore cosTheta RHS should have a minus sign.
• The formula in that chapter, listed right above the code block.
• Actual experiments... Initially I implemented h-g sampling based on the code above, which costed me two days to debug my code. The following experiments are based on pbrt-v3, and the code doesn't have the problem mentioned above. You will notice that we can not really distinguish between these two the incorrect results, even though one exhibits forward scattering and the other is backward.

correct g = 0.5	correct g = -0.5	incorrect g = 0.5	incorrect g =-0.5

3.3.3 Coordinate System From a Vector - Equation wrong

The equation in this section is wrong and does not fit the given implementation Link.

The "1-" should be moved in front of the fraction (out of the numerator). See also this post on math stackexchange: https://math.stackexchange.com/questions/4838905/coordinate-system-from-a-3d-unit-vector/4839260#4839260