Vect RandPosition(double radius)
{
Vect v;
do
{
v = new Vect(random.NextDouble() * (640 - 2 * radius) - (320 - radius), random.NextDouble() * (480 - 2 * radius) - (240 - radius));
} while (v.Length() < 85.0f);
return(v);
}
void AddBox(Space space)
{
const double size = 10.0;
const double mass = 1.0;
Vect[] verts =
{
new Vect(-size, -size),
new Vect(-size, size),
new Vect(size, size),
new Vect(size, -size)
};
double radius = verts[0].Length();
Vect position = RandPosition(radius);
var body = new Body(mass, Polygon.MomentForPolygon(mass, verts, Vect.Zero, 0.0));
space.AddBody(body);
body.VelocityUpdateFunction = planetGravityFunctionCallback;
body.Position = position;
// Set the box's velocity to put it into a circular orbit from its
// starting position.
double r = position.Length();
double v = Math.Sqrt(gravityStrength / r) / r;
body.Velocity = position.Perpendicurlar * v;
// Set the box's angular velocity to match its orbital period and
// align its initial angle with its position.
body.AngularVelocity = v;
body.Angle = Math.Atan2(position.Y, position.X);
var shape = new Polygon(body, verts, Transform.Identity, 0.0);
space.AddShape(shape);
shape.Elasticity = 0.0;
shape.Friction = 0.7;
}