Customer Reviews

Game Physics (Morgan Kaufmann Series in Interactive 3D Technology)

5 star:		(4)
4 star:		(1)
3 star:		(2)
2 star:		(0)
1 star:		(0)

 

 

I always love it when scientists and engineers, and mathematicians come along and review a game programming book. They go "oh! This is just ALL WRONG!!! AHHH!!!"

Please keep in mind this book is for physics simulations for video games. We can't yet simulate the universe on an atomic scale in a PC game and expect a frame rate of more than 1 frame per millenium at this point in time.

I own all all of Dr. Eberly's books and I find them all my most useful books. The only other graphics book I use alot is my Graphics programming by James Foley. The nice thing about Dr. Eberly's book is that the code for most of this is on his website, so if you get stuck on how to implement something looking at the source code can help you further understand the maths and equations. I recommend to buy this if you are willing to put in the effort to understand the maths, but if you have a phd already you might not need it than.

This book has much good information if you know exactly what you are looking for. However, its tone is very dry and academic and lacks a big picture perspective. It glosses over essential information on mechanics and in just 200 pages covers Newtonian and Lagrangian concepts. There are lots of equations, but the examples all use variables, thus making the examples no clearer than the equations they are supposed to be illustrating. There are no numerical examples at all.

Chapter 5, on physics engines, which the author himself says is the heart of the book, is woefully inadequate. He talks about the equations and features he wants to implement, and shows code snippets for the features, but there is one essential component that is missing - block diagrams and accompanying discussions that illustrate how all of these pieces fit together. A crate full of clearly labeled mechanical parts does not an automobile make.

Next we come to one of my areas of interest and one of the main reasons I bought this book in the first place - Chapter 6, "Physics and Shader Programs". The author certainly hits some fascinating topics - ocean waves, skin and bones animation, etc. However, once again the author skips what is between the basic physics equations that comprise these effects and the implementation of these equations and effects in code. The code that he does show is in NVidia's Cg language. So if you don't know Cg, the code is undecipherable. I would have preferred algorithmic pseudocode. Then I could implement the effects in the language of my choice.

The last four chapters of the book take an uptick in quality. These chapters are strictly on numerical methods, and I can't believe they are written by the same author that wrote the first six chapters. There are fairly good discussions and examples on the subjects of linear and mathematical programming, ordinary differential equations, numerical methods, and quaternions, and also how these mathematical methods fit into solving problems in physics. They are not self-contained tutorials, but they are a good summary and review for the physics student who has already had some exposure.

I really can't recommend this book as anything but a reference. Its merits are mainly the tying of mathematical methods to physics and good basic discussions on some topics. But where the rubber meets the road - answering the questions of "How does one go about building a physics engine?" and "How do I implement physics within the confines of a computer game?" I think that this book is a failure. I give it three stars only because the author obviously put a lot of effort into the work, and what he does write is not incorrect.

If you are interested in game physics I recommend "Physics for Game Programmers" by Grant Palmer. It takes an engineer's viewpoint of the subject and features plenty of examples in Java of how to simulate explosions, lasers, and the motion of various classes of vehicles. There is no discussion of game engines, though. A good reference on college level physics can be found in the most recent edition of Schaum's Outline of College Physics.

This is a great book on physics simulation, covering most of the mathematical methods and tricks. Some people would complain that's very mathematically intensive, but I don't see another way to do it without being superficial. This book, however, goes very deep in almost every aspect of rigid body simulation, and covers some aspects of non-rigid body simulation as well, which is an emerging trend.

I would suggest only one change to it: there's a chapter on shaders which is pretty much useless - it's very superficial as it doesn't teach shader writing, and doesn't teach hwo to use shaders for physics - I'd suggest that it be changed to include GPGPU methods for physics instead.

Other than that, the book is great, and the only one I've seen that actually covers heavy-duty, real-world simulation and not just silly approximations for special cases.

For many videogames that emulate the real world, an accurate use of physics has become essential to take advantage of players' intuition. In some ways, this is the next natural step beyond a realistic, real time rendition of images, as in Doom or Quake. Those and other games used simple optics and trigonometry to derive accurate images.

But as computers get more powerful, and players might find themselves driving cars, for example, then having these vehicles respond accurately when driven became the next logical step in simulation.

The book covers Newtonian mechanics, because that is what we are typically familiar with. If you are a physicist, you should recall that historically there were 2 great advances within this - Hamiltonian and Lagrangian methods. (Cf. Goldstein's "Classical Mechanics".) A little ironic, wouldn't you say, that now some jobs in applying these are for games?! Who would have thought it, some twenty years ago.

The book is good for helping you focus on what objects in the system you should be modelling. Part of your experience comes in deciding this level of detail. Actually, this is not restricted to games, but to any physical system that you are analysing.

The graphics in this book are really a secondary consideration. Stay focused. Model the system FIRST. Then attend to the views. Even though the views are what the player sees.

To this end, you should be pleased to know that the author sticks to graphics standards like OpenGL, which can be ported to most current computers. So you don't have to invest your time in learning some restricted graphics language.

Undoubtedly this is a must-have for people who are serious about developing real-time computer graphics simulations with physically based modeling.

This book can be compared with Coutinho's "Dynamic Simulations of Multibody Systems". I believe the latter covers more materials, but Eberly's is easier to read. The book would be almost sufficient if you also have his previous book "3D Game Engine Design".

I am not sure why the author wrote chapter 4 and 6. I suppose these can be left out. It would have been more compact.

My interest is physics and physics simulations, not gaming per se...so my observations should be viewed in that light.

The main problem with this book is the treatment is incomplete, superficial, or just wrong (from a physics/math point of view), and the typical programmer/computer scientist is not likely to know it. I am reminded of the great fluid dynamicist von Karmen's definition of an engineer as that person who perpetuates the mistakes made by the previous generation. The REASON a game programmer can get away with this is that he is not testing his results by real experiment...his world is a computer generated simulation with arbitrary approximations to physical laws that the programmer deems to impose.

The other problem is that there are usually a multitude of techniques that one can pick to solve a given mechanics problem...and what would have been really valuable is if the author had shown why a particular method is better (for example, Newton's Laws vs. Lagrange's Equations) when the time comes to code the algorithm. We are not looking for Eberly primarily to teach us physics (but if he makes the attempt, it should be correct!)-that is always going to be the job of physics courses. Instead, he needs to tell us which method is useful for coding and why-this, sadly, he has not done.

As an illustration of what I mean...look at how Petzold in `Programming Windows with C#' discuss the elementary process of using GDI+ to draw a curve. There are two approaches, using rectangular coordinates, or using parametric equations (polar coordinates). Petzold explains WHY the parametric approach is superior from a programming point of view.

Any advanced sophomore or junior physics student will know most of the physics presented here (classical mechanics)...but in addition, they will also know the CORRECT statement of conservation of angular momentum (the author got it wrong) ...AND they will have a deeper understanding, because they will have likely studied something like Marion's Classical Dynamics which is rigorous and physical. Especially egregious is Eberly's twice incorrectly defining an inertial reference frame. In classical mechanics, an inertial reference frame is one in which Newton's laws are valid.

Same comment for the math...The math is maybe sophomore/junior level (except for the Quaternions)...but it is not rigorous nor is it motivated, and sometimes it is wrong. Compare Eberly's terse treatment of the delta function with Marion's motivated and physical discussion. Also, we see things like interchange of limits and integration, without explaining when this is mathematically legal. Then there is the unmotivated vector spaces treatment. Eberly goes to the effort to define a field, but then restricts his definition of a vector space to having real coefficients...Then why bother defining fields if you are not going to use them. We are given the mathematician's definition of the determinant (i.e., the unique, alternating, n-linear function with identity) but this is completely useless from a computational view! If Eberly wants to present some advanced linear algebra, then some tensor analysis would have served the game programmer better, as it is often used in continuum mechanics and fluids, neither of which are discussed by the author. He had a perfect opportunity in the Affine Algebra chapter when he stumbles upon the Levi-Civita tensor, which he then dismisses as unimportant! The Affine Algebra chapter is really bad from both a physics and a geometry view. First, a physicist does not think of a vector as something with direction and magnitude, and a geometer is more inclined to think of them as a derivation. Second, affine spaces are too weak a tool to use to distinuish points from vectors, though we do mod out the origin..this really needs a manifold with vector fields and parallel translation. Third, linear algebra is the study of vector spaces and isomorphism.

There is a chapter on numerical methods, but again incomplete! We should have at least got Numerov's method and some Monte Carlo techniques.

The chapter on shading is ridiculous from a physics point of view. Essentially we have Snell's law, and a cursory reference to Fresnel and that's it...Evidently, the author was not up to discussing some real physics ala Maxwell. Why spend so much time on classical mechanics, and then almost totally dismiss optics with a non-physical discussion? We don't even get Huygens principal. But we do get a wrong definition of polarization of light.Thankfully, he did not try to define helicity.

In summary, this book has two uses:
1) It presents a list of physics and some numerical methods which the game programmer will find useful, and which he will then go ELSEWHERE to actually learn. (I can recommend Landau (of OSU, not Russia) "Computational Physics" and also the CUPS Physics Simulations books for excellent starters.)
2) There is the happy possibility that a budding game programmer, in his pursuit of the knowledge to build a better computer game, will discover the much more interesting game called Physics.

Escrito para prefesores !
No es un libro que explique las cosas "con manzanitas".