Game Development Reference
In-Depth Information
Building the ODE physical library
This recipe is dedicated to the building of the open source ODE (Open Dynamics Engine)
physical simulation library, which is one of the oldest rigid body simulators for
interactive applications.
Getting ready
Download the most recent source code from the library home page:
http://www.ode.org/
download.html
.
How to do it...
1.
Compiling ODE is no different from other libraries. One subtle point, is the selection
between
single
and
double
loating-point precision. Standard compilation
involves the
autoconf
and
automake
tools, but here we just prepare
Android.
mk
,
makefile
as usual, and
odeconfig.h
. We need to deine either the
dDOUBLE
or
dSINGLE
symbol there to enable the
single
or
double
precision calculations.
There is this line in the beginning of the
odeconfig.h
ile:
#define dSINGLE
2.
It enables the single-precision, 32-bit loating point calculations which are suficient
for simple interactive applications. Changing the value to
dDOUBLE
enables the
double-precision, 64-bit loating point calculations:
#define dDOUBLE
3.
ODE is rather complex software and it includes the Ice collision detection library,
which unfortunately, has compilation problems when the strictest possible settings
of the Clang compiler are used. However, it is easily ixed by commenting out the
contents of the
_prefetch
function in the
OPCODE/Ice/IceUtils.h
ile.
How it works...
Since ODE calculates positions and orientations of the rigid bodies in 3D space, we have to
set up a tiny 3D rendering pipeline on top of the simple 2D rendering we have done in this
chapter. To demonstrate the ODE library we cannot avoid some 3D math. All objects in the
scene (world) have their coordinates and orientations speciied as a pair of values consisting
of a 3D vector and a quaternion. We convert them to a 4 x 4 afine transformation matrix.
Then, we follow the chain of coordinate transforms: we convert the object space to world
space, world space to camera space and the camera space to post-perspective space with
a multiplication by the projection matrix.
