Contact Physics by Roderick Kennedy [01.21.03] Not long ago, most game physics focused on flight models and contact physics wasn't part of the picture. A plane can be modelled very accurately as a point mass in the sky, and the challenge for the physics programmer was to get the right lift coefficients, drag, and engine model. Today, flying and shooting is a niche market, games are much more close-in, and it's ground-based car simulations like World Rally Championship that occupy the hardcore sim niche that flight sims once did. We now have the challenge of making games feel solid, creating an illusion of tangible physical presence. With today's advanced graphics you really notice when the physics are lagging behind. Roderick Kennedy shows how solid contact physics can be implemented and describes some of the problems the programmer will encounter.

Advanced Character Physics by Thomas Jakobsen [01.21.03] The use of physically-based modeling to produce nice-looking animation has been considered for some time and many of the existing techniques are fairly sophisticated. Much effort has been put into the construction of algorithms that are accurate and reliable, but for games and interactive use accuracy is really not the primary concern. The important goals for games are believability (including stability)and speed of execution. This feature explains the basic elements of an approach to physically-based modeling which is well suited for interactive use. It is simple, fast, quite stable and allows for simulation of both cloth; soft and rigid bodies; and even articulated or constrained bodies using both forward and inverse kinematics.

Outsourcing Reality Integrating a Commercial Physics Engine by Matt Maclaurin [01.21.03] Licensing rendering engines is now a well-established practice, with great potential cost and time savings over the development of a single game. As game developers reach for new forms of gameplay and a better process for implementing established genres, the wisdom of licensing physics engines is becoming inescapable. This sophistication does come with a cost. Physics engines do more than just knock over boxes, and the interface between your game and a physics engine must be fairly complex in order to harness advanced functionality. Whether you have already licensed an engine and want to maximize your investment or you’re just budgeting your next title, gaining a better understanding of the integration process will save a lot of trial and error, and hopefully let you focus on better physics functionality while spending less time watching your avatar sink through the sidewalk.

What a Designers Should Know About Physics by Fred Marcus [01.21.03] Badly tuned physics can be a disaster: A vehicle can become impossible to control, objects can get in the way of the player, things just don’t feel right and what should have made the game fun just generates frustration. As a game designer, you are responsible for the fun of the game, so it is your role to make sure physics are tuned properly and not left solely to a programmer’s whim. If you don't play a role designing and tuning the physics, your game might ship with you unhappy with the tuning, wishing you had learned more sooner (also called regrets) and you will miss a lot of opportunities to discover fun things you might have done with the physics. You will have to get your hands dirty and tweak many variables many times before you get some good results.