Customer Review

18 of 18 people found the following review helpful
2.0 out of 5 stars Download it for free!, 11 Feb 2005
By A Customer
This review is from: Game Physics (The Morgan Kaufmann Series in Interactive 3D Technology) (Hardcover)
A few days ago, I found David Baraff's '97 Siggraph course notes - they're available for free download from his website (search Baraff on Google). I realised, as I leafed through them, that much of this book is just a complete rip-off of these notes. All the author has really added is a load of typos and some *seriously* bad explanations... this really deserves a paragraph of its own...
Now it's not often that a mathematical mind capable of this sort of explanation comes into being. I really don't know how he does it! But honestly, Dave is undeniably the worst maths writer I have *ever* come across, and this is after doing a maths degree. Now I know that maths can be hard to explain, but this is a disaster - there is sooo much irrelevant information, but you can't skip any of it because it's always mixed with important stuff (which is impossible to find without reading everything). This is made particularly poignant by the fact that Baraff is Eberly's very antithesis - his explanations are lucid and crystal clear. Note that I make these criticisms not only on the basis of this book, but also after reading Eberly's "Geometric Tools for Computer Graphics", for which I notice there are already some slightly scathing reviews in existence.
One thing that particularly gets my goat with this book is that the physics engine Eberly develops, he claims, guarantees non-penetration of objects (p280). But then he goes and makes approximations in the collision detection phase which violate this!!! Specifically, the collision detection he describes only takes account of linear velocity - rotational movements during a time step are applied as an afterthought (see p343), and allow for objects to becomes locked together. Also, throughout the book he analyses in terms of real numbers (rather than floating point numbers) including testing for "boundary intersection" (i.e. when two objects intersect *only* at their boundaries) as a separate event from interpenetration. But obviously, when time is discretised and numbers are floating point, one simply cannot deal with things in this way - it's like testing one f.p. number being exactly equal to another. I really can't believe this oversight! Overall, the book has a feel of each chapter being completely independent and unaware of the others, as though they're all plagarised from different papers without any consideration of continuity or interdependence.
To be fair, there are one or two things that this book has going for it. There's a chapter which explains the absolute basics of pixel shading (albeit now out-of-date) and mentions a few examples of how to use it for some optical effects, but no real explanations are given - you're left to read the source on the CD. And there's enough about collision detection to get you started, but if you're serious about it you'll need to (guess what?!) buy another book in his Series in Interactive 3D Technology (specifically "Collision Detection in Interactive 3D Environments").
Anyway, when I bought this book a few months ago, it was because I wanted to know about how to do collision detection and response in games. I write this review because I *wish* I had known that the relevant information was available on the web for free before I forked out over 30. Take a look at Baraff's papers, and their references (which you'll mostly be able to download for free from ACM or CiteSeer - search for these sites on Google). Not only will you get the info you need, you'll also get a feel for how to read research papers, if you don't already (it's no harder than reading books, just slightly more focussed). Eberly has literally contributed less-than-nothing with this book - the only section worth reading is the bibliography.
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