public Wheel(
b2World b2world,
double x,
double y,
double width,
double length,
bool revolving,
bool powered
)
{
this.revolving = revolving;
this.powered = powered;
this.Initialize = car =>
{
/*
wheel object
pars:
car - car this wheel belongs to
x - horizontal position in meters relative to car's center
y - vertical position in meters relative to car's center
width - width in meters
length - length in meters
revolving - does this wheel revolve when steering?
powered - is this wheel powered?
*/
var position = new double[] { x, y };
//this.car=pars.car;
//this.revolving=pars.revolving;
//this.powered=pars.powered;
//initialize body
var def = new b2BodyDef();
def.type = b2Body.b2_dynamicBody;
def.position = car.body.GetWorldPoint(new b2Vec2(position[0], position[1]));
def.angle = car.body.GetAngle();
this.body = b2world.CreateBody(def);
//initialize shape
var fixdef = new b2FixtureDef();
fixdef.density = 1;
fixdef.isSensor = true; //wheel does not participate in collision calculations: resulting complications are unnecessary
var fixdef_shape = new b2PolygonShape();
fixdef.shape = fixdef_shape;
fixdef_shape.SetAsBox(width / 2, length / 2);
body.CreateFixture(fixdef);
var jointdef = new b2RevoluteJointDef();
//create joint to connect wheel to body
if (revolving)
{
jointdef.Initialize(car.body, body, body.GetWorldCenter());
jointdef.enableMotor = false; //we'll be controlling the wheel's angle manually
}
else
{
jointdef.Initialize(car.body, body, body.GetWorldCenter()
//, new b2Vec2(1, 0)
);
jointdef.enableLimit = true;
//jointdef.lowerTranslation = 0;
//jointdef.upperTranslation = 0;
}
b2world.CreateJoint(jointdef);
#region setAngle
this.setAngle =
(angle) =>
{
/*
angle - wheel angle relative to car, in degrees
*/
body.SetAngle(car.body.GetAngle() + angle.DegreesToRadians());
};
#endregion
#region getLocalVelocity
Func<double[]> getLocalVelocity = delegate
{
/*returns get velocity vector relative to car
*/
var res = car.body.GetLocalVector(car.body.GetLinearVelocityFromLocalPoint(new b2Vec2(position[0], position[1])));
return new double[] { res.x, res.y };
};
#endregion
#region getDirectionVector
Func<double[]> getDirectionVector = delegate
{
/*
returns a world unit vector pointing in the direction this wheel is moving
*/
if (getLocalVelocity()[1] > 0)
return vectors.rotate(new double[] { 0, 1 }, body.GetAngle());
else
return vectors.rotate(new double[] { 0, -1 }, body.GetAngle());
};
#endregion
#region getKillVelocityVector
Func<double[]> getKillVelocityVector = delegate
{
/*
substracts sideways velocity from this wheel's velocity vector and returns the remaining front-facing velocity vector
*/
var velocity = body.GetLinearVelocity();
var sideways_axis = getDirectionVector();
var dotprod = vectors.dot(new[] { velocity.x, velocity.y }, sideways_axis);
return new double[] { sideways_axis[0] * dotprod, sideways_axis[1] * dotprod };
};
#endregion
#region killSidewaysVelocity
this.killSidewaysVelocity = delegate
{
/*
removes all sideways velocity from this wheels velocity
*/
var kv = getKillVelocityVector();
body.SetLinearVelocity(new b2Vec2(kv[0], kv[1]));
};
#endregion
};
}