Physically Based Modeling

PBM Waves Demo

About

This Physically Based Modeling library is a C++ implementation of the techniques and interfaces described in the book Physically Based Modeling for Computer Graphics (ISBN 0-12-079880-08) by Ronen Barzel.

Physically Based Modeling is a member of the IronWorks.cc family of projects.

Documentation

There is no documentation other than Barzel's book. However, the book is a very complete description of all the modules and interfaces implemented in the library.

Demos

Physically Based Modeling includes a self-extracting ZIP file which includes some programs which demonstrate various features of the library. You can get it here, on the SourceForge 'Files' page.

Demo Programs

Name	Description
Figure8	Demonstrates how to animate a body through a fixed kinematic path
Pendulum	Animates a Pendulum swinging through a magnetic field
RigidBodies	Animates several rigid bodies connected to fixed points in space, and to each other
SpringsAndSpheres	Animates several spheres connected with springs to fixed points in space and to each other
Viewer	This is a generic program which reads in a description of geometry and constraints from a text file, and animates the results. The grammar is contained in the file PBM.yac in the `parser` package
Waves	This demo animates droplets falling into a liquid pool. It can run as a standalone program or as a screensaver.
WreckingBall	Demonstrates combining kinematic motion with force-calculated motion.

Source Code

You may access the source code by anonymous CVS, or you may browse it on-line. See the CVS Page at SourceForge for more information. There are 4 modules that you may 'checkout':

pbmlib : This is the Physically Based Modeling library as described in the book. It consists of the following packages. Each of these packages is in its own directory and C++ namespace, and has a sub-project which tests the package.
- support : Tracing utilities, ID, IDSet, Enumeration, a simple Memory Pool used by the vecmath package.
- vecmath : Optimized matrix and vector classes and operations. Especially optimized 3x3 Matrix and 3-Vector.
- misc : Containers, IDForest (a graph of IDs), other utilities.
- coords : Implements Vector, Location, Orientation, Location, Frame, InstFrame (a frame in motion), Basis, 2Tensor.
- kinematic : Implements Kinematic (fixed-path) motion, with classes for BodyPt (a point on a physical body), State (equivalent to an InstFrame), StatePath, HierConfig (a tree structure of rigidly connected physical bodies), InterpolationPath.
- structurednumerics : C++ interfaces to low-level numerical algorithms. Includes Gather/Scatter (for transferring data between arrays and objects), a SparseMatrix, Interpolator, LinearSolver (solves a system of linear equations using matrix methods), Runge-Kutta ODE integration, and ODEExt (a wrapper around the ODE solver which spline-interpolates between solution data points).
- forces : Classes for applying body forces to objects. Includes abstract definitions of linear constraints.
- constraints : Implementations of specific constraints which can be applied to bodies, including AxisAlignedSpring, AxisToAxis, PerpendicularAxis, RelativeAngularVelocity.
- rigidbody : Ties everything together with the RBSystem and RBSolveForward clasess, which solve a system of bodies and forces forward in time. Other classes in this package include RBState (the dynamic state of a rigid body), PtMass (point mass), MassDist (a scalar mass, center of mass, and inertia tensor), Motive (a force), ApplMotive (a Motive applied to a body), RBBodyPt (a body point on a rigid body).
demos : Source code for the demos packaged in the self-extracting demos download. See here for a list of the programs included in the download.
external : Contains source code and binaries for external libraries which are used to build the Physically Based Modeling library and demo programs. Among the external code used is:
- libI77.lib, libF77.lib : The FORTRAN runtime libraries. I'm not a FORTRAN expert but I believe they are analagous to the C runtime libraries (libc or msvcrt on Windows).
- SLATEC mathematical library. See here for the canonical home of SLATEC. See here for some instructions on how to call SLATEC functions from C. The external/slatec directory contains FORTRAN and C (generated by a FORTRAN to C converter) source code for the SLATEC code used by PBM, downloaded from Netlib.
www : The source code and images for this web site

Other Libraries Required to Build PBM

In addition to the code in the external package, there are some other libraries you'll need to build PBM. Free implementations are available of all the required libraries. The packages are quite large so I do not include them in the PBM source tree.

BLAS (Basic Linear Algebra Subroutines). See here for a BLAS FAQ. Essentially it is a standard linear algebra library. There are several implementations of the BLAS available, for any platform you might care to use. For Intel processors (Win32 or Linux), I recommend the Intel Math Kernel Library for Intel Architecture. You can find other BLAS implementations with a quick Google search.
LAPACK (Linear Algebra PACKage). LAPACK is another (higher-level) standard linear algebra library, with implementations for every platform. I believe that LAPACK comes with the Intel Math Kernel Library for Intel Architecture. You can also get source and binaries from the LAPACK home page at Netlib.
( Optional ) PBM makes an effort to make efficient use of memory. Still, the Win32 implementations of malloc() and new() are not very good, and memory allocation can show up as a hotspot in profiles of PBM applications. If you can afford it, I recommend that you use SmartHeap. It works like a charm. PBM applications will build and run just fine without it; it's just enhances performance.

Finally, PBM currently builds with Microsoft Visual C++. The code is not written to reference any Windows-specific functionality, so there shouldn't be any major roadblocks to building it on a UNIX platform. ( The only one problem I can think of is how good the support for templates is in GCC ). Certainly, if you build PBM on any non-Windows platform please let me know about it. In fact, by the terms of the LGPL license, you are required to send me your modifications. The Visual C++ build uses the multi-threaded DLL runtime library ( msvcrt and msvcirt ). If you try and link it with other code that was built for the static C runtime ( libc ) you will get nasty un-resolvable link errors. You'll have to re-compile one library or the other in order to make them compatible.

PBM Viewer Demo Showing
'wheelassembly.txt'

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