void add_box()
{
const float size = 10;
const float mass = 1;
cpVect[] verts = new cpVect[] {
new cpVect(-size, -size),
new cpVect(-size, size),
new cpVect(size, size),
new cpVect(size, -size)
};
float radius = cpVect.cpvlength(new cpVect(size, size));
cpVect pos = rand_pos(radius);
cpBody body = space.AddBody(new cpBody(mass, cp.MomentForPoly(mass, 4, verts, cpVect.Zero, 0.0f)));
body.SetVelocityUpdateFunc(
(s, f1, f2) => planetGravityVelocityFunc(body, s, f1, f2)
);
body.SetPosition(pos);
// Set the box's velocity to put it into a circular orbit from its
// starting position.
float r = cpVect.cpvlength(pos);
float v = cp.cpfsqrt(gravityStrength / r) / r;
body.SetVelocity(cpVect.cpvmult(cpVect.cpvperp(pos), v));
// Set the box's angular velocity to match its orbital period and
// align its initial angle with its position.
body.SetAngularVelocity(v);
body.SetAngle(cp.cpfatan2(pos.y, pos.x));
cpShape shape = space.AddShape(new cpPolyShape(body, 4, verts, cpTransform.Identity, 0.0f)); //cpTransformIdentity
shape.SetElasticity(0);
shape.SetFriction(0.7f);
}
