CS 282 Simulation Physics Lecture 1: Introduction to Rigid-Body Simulation 1 September 2011 Instructor: Kostas Bekris Computer Science & Engineering, University of Nevada, Reno

CS 282 What does “Simulation Physics” involve? Simulation physics is a big subject area that relates to many fields Physics encompasses many subfields for a variety of physical systems it is interesting to build simulations for each one of these subfields e.g., a popular book on computational physics includes material on: The Motion of Falling Objects The Two Body Problem Chaotic Motion of Dynamical Systems Many Particle Systems Waves Electrodynamics Gases and Heat Flow Fluids Quantum Systems

CS 282 Our Focus We are going to focus on particle and rigid-body simulation i.e., building simulators for the physics subfield of “mechanics” We have a Computer Science and Engineering perspective we will learn about the underlying physics but we are interested in how to implement them on a computer and we are going to practice implementing various simulations A more accurate name for this class: “Algorithms and Mathematical Tools for the Physical Simulation of Rigid-Bodies and their Interactions” Too long... So, “Simulation Physics”!

CS 282 How to model systems that bounce, float, fly and roll!

CS 282 Why in a Computer Science and Engineering curriculum? Because there is an increasing need for physics-aware software Games  Game players are sophisticated and demanding!  Physics often matters to them.  A game loses credibility fast if the physics it uses is incorrect. Scientific and Commercial Simulations  scientists (e.g., roboticists), who are interested in designing physics-aware algorithms  government (e.g., military), which is interested in training simulations or studing the robustness and safety of mechanical systems  industry (e.g., factories), which are interested in the predictive capabilities of simulation to improve the production process and reduce cost “If you are looking for realism in a flight simulator, then this game is the way to go. The experience is breathtaking as you can almost feel the plane’s reaction to its surroundings” X-treme Gaming Radio’s evaluation of MS Flight Simulator ‘04 “Now, as much as the series has tried to tout realistic physics and control, I just have to say that there is no physical equation for a hovering jet bike. They just don’t exist.” GameTour review of JetMoto3

CS 282 Why in a Computer Science and Engineering curriculum? Because it will make you a better Computer Scientist and Engineer as it provides a good setup to: Hone your programming skills  Forces you to do mathematical programming, which is often required in the “real world” Make you think about proper abstractions, data structures and algorithms  Failure to think about the proper tools will quickly make your simulation software unmanageable Learn some helpful tools and processes for software engineering  We will introduce helpful tools for software engineering Show how “visual” and related to the “physical” world this field is  You get the pleasure of “seeing” your software in action

CS 282 It involves traditional challenges of Computer Science and Engineering. In the simulations you will build a tradeoff will always be arising Balance accuracy/physical realism with computational cost Depending on the needs of the application This is a typical tradeoff for Computer Scientists and Engineers in the real world We have to worry about the accuracy of the underlying physical models, robustness of the implementation, as numerical problems arise often computational cost of the algorithms employed Why in a Computer Science and Engineering curriculum?

CS 282 Why in a Computer Science and Engineering curriculum? Because today it is easy to do a good job in simulating physics Availability of computational power:  It used to be the case that “all that complicated math will slow my software (e.g., game), let’s cheat instead”!  Modern processors are fast enough to zip through most physical models (e.g., in games rendering and AI takes most of the time)  Processors will be getting even faster into the future through the proliferation of parallelization The math involved are not and should not be scary for you  Physics has a reputation for being really hard.  Most of the physical models you need to be aware of are reasonably simple.  The more you are exposed to the underlying math (e.g., differential equation) the easier it gets to deal with new challenges!