Game Development Reference
In-Depth Information
We first check whether an active
rigidBody
variable is assigned to the geometry. If it
is assigned, then we retrieve the position of the
rigidBody
variable using the
this.
rigidBody.get_currentState().position
function. We convert the position
of
rigidBody
to the
vec3
object and set the
location
property of the sphere. The
modelMatrix
parameter of the sphere is initialized to the identity matrix and then
the sphere's
modelMatrix
is translated by the
rigidBody
variable's position.
So basically, we change the location of the sphere to the
rigidBody
variable's
location, and if
rigidBody
for that object does not exist, then we use the object's
location and rotational values.
Open the
07-Simple-Physics-Sphere-Falling.html
file in your editor.
We initialize our physics engine in the
init_jiglib()
function. This function is
invoked when the graphics library is initialized in the
start()
function:
function start() {
...
init_jiglib();
...
}
function init_jiglib() {
system = jigLib.PhysicsSystem.getInstance();
system.setCollisionSystem(); // CollisionSystemBrute
system.setSolverType("FAST");
system.setGravity(jigLib.Vector3DUtil.create( 0, -9.8, 0, 0 )
);
var ground = new jigLib.JPlane();
ground.set_y(0);
ground.set_rotationX(90);
ground.set_movable(false);
system.addBody(ground);
}
In the
init_jiglib()
function, we first initialize our physics engine and then
initialize our collision system using the brute force algorithm (each object is checked
for collision) and set the solver type to
FAST
. Then, we initialize gravity in our system
(
system.setGravity(jigLib.Vector3DUtil.create( 0, -9.8, 0, 0 ) );
). As
the physics system follows the upward direction along the
y
axis, we set our gravity
to a negative value.
