It’s just over a year ago now that I posted an analysis of citation counts in the bibliographies of the first three editions of Physically Based Rendering. Back then I promised an update with statistics for the forthcoming fourth edition “in the next few weeks.” That turns out to have been rather optimistic, but here we now are with results finally available.

The fact that these results are ready means that we’re done fiddling with the text; we will shortly be handing it over to the publisher so that the book production process can begin. We have switched to MIT Press for the fourth edition and it’s been a fine experience working with them so far; we’re optimistic that our interests are all well aligned in producing a quality book, much more so than with the previous corporate conglomerate that shall not be named. Happily, MIT Press has agreed that we can continue to post a free edition of the book online. (The current plan is for that to be made available roughly six months after the print edition hits the shelves.) However, that brings us to our first point of drama in this bibliographical vanity contest: the online edition will be a superset of the print edition and so there are differences between their bibliographies.

The differences between the two versions are due to the amount of new content that we wrote for the fourth edition; all in all, it would be about 1,600 printed pages. That’s too much for a single volume, at least if one wants paper that isn’t newspaper-thin and a binding that won’t fall apart. Thus, Wenzel and I went through the exercise of rejiggering the book into a 1,200 page version for print while maintaining the full text for the online edition. In deciding what would be online-only, we looked for content that was mostly independent of the rest of the book and was little-changed from the third edition. As examples, both the section on realistic camera models and the chapter on bidirectional light transport will not be there in the print edition this time.

The print edition still includes citations and discussion of previous work for topics that are not included in its text, though not as much of it as in the online edition—it doesn’t make sense to go into as much depth in the citations when the text doesn’t deeply discuss the corresponding topics. Therefore, here I will report the results for both the print and online editions. No doubt there will be years of arguments to come about which is the more proper measure—one might argue that the online edition’s bibliography is the canonical one, as it reflects what would be printed if physical limitations didn’t intrude, or one might argue for the print edition in that those citations earned consumption of actual paper and not just electrons. We will leave that question to be resolved by future historians of computer graphics.

Finally, a few notes on methodology: as before, the following is a simple count of how often each name appears in the bibliography. Editing a book or a conference proceedings doesn’t count, but otherwise every citation is counted equally—from a single-author SIGGRAPH paper to a blog post. The citations include work through SIGGRAPH 2021 but nothing published subsequently. Yes, SIGGRAPH Asia papers are now out, but we had to draw a line somewhere in order to get that thing out the door.

As before, many caveats are in order about how arbitrary a measure this is. Another to mention today is the impact of the fine series of Eurographics State of the Art Reports (STARs), twelve of which appear in the fourth edition’s bibliography. For topics that are not central to the book (e.g., texture synthesis), we will often cite a STAR and only a few additional publications rather than comprehensively survey previous work. Thus, there is an irony in successfully developing a new area of research to the point that it merits a STAR: in our bibliographic measure, a lengthy publication record may end up collapsed into a STAR and a few additional citations, putting one lower than one would have been otherwise.

With that, here are the results for all four editions—author last names with citation counts:

1st (2004) 2nd (2010) 3rd (2016) 4th (print, 2022) 4th (online, 2022)
Greenberg (26) Jensen (31) Jensen (33) Jarosz,
Jensen (35)
Jensen (40)
Shirley (25) Shirley (29) Shirley (31) Ramamoorthi (32)  Ramamoorthi (38)
Hanrahan (22) Greenberg,
Hanrahan (27)
Keller (27) Keller,
Shirley (31)
Hanika (36)
Jensen (16) Ramamoorthi (23)  Wald (25) Hanika,
Jakob (30)
Dachsbacher (33)
Arvo (14) Wald (18) Greenberg,
Hanrahan (24)
Wald (29) Jakob,
Shirley (32)
Mitchell (13)  Keller (17) Slusallek (21) Slusallek (27) Keller (31)
Keller (12) Arvo,
Slusallek (16)
Ramamoorthi (19) 
Marschner (26)
Wald (30)
Torrance (10)
Mitchell (13) Arvo,
Seidel (17)
Křivànek (25) Marschner,
Slusallek (27)
Ward (8)
Walter (12)
Jarosz (16) Hanrahan,
Novák (23)
Hachisuka (25)

Henrik continues his reign, though he now shares the top spot with Wojciech Jarosz, who had not a single appearance in the first edition’s bibliography. The smallest of lexicographical differences—“a” before “e”—puts Wojciech first in the alphabetical ordering. Fittingly, Wojciech was Henrik’s Ph.D. student, so I have to assume that for Henrik the bitterness of sharing the glory is balanced by the sweetness of a former student’s achievement.

Other than Henrik, Alex Keller and Pete Shirley are the only others who made the list for all four editions, though Pat Hanrahan also has that distinction if one neglects the online 4th edition. (Surely Pat will therefore be out there arguing vigorously that the print edition is canonical.)

Ravi Ramamoorthi has displaced Pete Shirley from his long-held number two position, though just by a hair, at least in the print edition. Johannes Hanika has also rocketed up in the standings, making an especially quick climb given that he was not cited in either the first or the second editions. Carsten Dachsbacher has also climbed rapidly, starting from one citation in the first edition, two in the second, and 10 in the third. Finally and fittingly, Jaroslav Křivànek is up there in the latest edition as well.

There you have it. I must admit my disappointment at seeing that the top two spots had the same names for both versions of the fourth edition—all the less potential controversy over which version is the canonical one, though there’s enough motion farther down the list that one might hope for some sparks in the future.