public ApplyForce()
{
World.Gravity = new Vector2(0.0f, 0.0f);
const float restitution = 0.4f;
Body ground;
{
var bd = new BodyDef();
bd.Position.Set(0.0f, 20.0f);
ground = World.CreateBody(bd);
var shape = new EdgeShape();
var sd = new FixtureDef();
sd.Shape = shape;
sd.Density = 0.0f;
sd.Restitution = restitution;
// Left vertical
shape.Set(new Vector2(-20.0f, -20.0f), new Vector2(-20.0f, 20.0f));
ground.CreateFixture(sd);
// Right vertical
shape.Set(new Vector2(20.0f, -20.0f), new Vector2(20.0f, 20.0f));
ground.CreateFixture(sd);
// Top horizontal
shape.Set(new Vector2(-20.0f, 20.0f), new Vector2(20.0f, 20.0f));
ground.CreateFixture(sd);
// Bottom horizontal
shape.Set(new Vector2(-20.0f, -20.0f), new Vector2(20.0f, -20.0f));
ground.CreateFixture(sd);
}
{
var xf1 = new Transform();
xf1.Rotation.Set(0.3524f * Settings.Pi);
xf1.Position = xf1.Rotation.GetXAxis();
var vertices = new Vector2[3];
vertices[0] = MathUtils.Mul(xf1, new Vector2(-1.0f, 0.0f));
vertices[1] = MathUtils.Mul(xf1, new Vector2(1.0f, 0.0f));
vertices[2] = MathUtils.Mul(xf1, new Vector2(0.0f, 0.5f));
var poly1 = new PolygonShape();
poly1.Set(vertices);
var sd1 = new FixtureDef();
sd1.Shape = poly1;
sd1.Density = 2.0f;
var xf2 = new Transform();
xf2.Rotation.Set(-0.3524f * Settings.Pi);
xf2.Position = -xf2.Rotation.GetXAxis();
vertices[0] = MathUtils.Mul(xf2, new Vector2(-1.0f, 0.0f));
vertices[1] = MathUtils.Mul(xf2, new Vector2(1.0f, 0.0f));
vertices[2] = MathUtils.Mul(xf2, new Vector2(0.0f, 0.5f));
var poly2 = new PolygonShape();
poly2.Set(vertices);
var sd2 = new FixtureDef();
sd2.Shape = poly2;
sd2.Density = 2.0f;
var bd = new BodyDef();
bd.BodyType = BodyType.DynamicBody;
bd.Position = new Vector2(0.0f, 3.0f);
bd.Angle = Settings.Pi;
bd.AllowSleep = false;
_body = World.CreateBody(bd);
_body.CreateFixture(sd1);
_body.CreateFixture(sd2);
var gravity = 10.0f;
var I = _body.Inertia;
var mass = _body.Mass;
// Compute an effective radius that can be used to
// set the max torque for a friction joint
// For a circle: I = 0.5 * m * r * r ==> r = sqrt(2 * I / m)
var radius = (float)Math.Sqrt(2.0f * I / mass);
FrictionJointDef jd = new FrictionJointDef();
jd.BodyA = ground;
jd.BodyB = _body;
jd.LocalAnchorA.SetZero();
jd.LocalAnchorB = _body.GetLocalCenter();
jd.CollideConnected = true;
jd.MaxForce = 0.5f * mass * gravity;
jd.MaxTorque = 0.2f * mass * radius * gravity;
World.CreateJoint(jd);
}
{
var shape = new PolygonShape();
shape.SetAsBox(0.5f, 0.5f);
var fd = new FixtureDef();
fd.Shape = shape;
fd.Density = 1.0f;
fd.Friction = 0.3f;
for (var i = 0; i < 10; ++i)
{
var bd = new BodyDef();
bd.BodyType = BodyType.DynamicBody;
bd.Position.Set(0.0f, 7.0f + 1.54f * i);
var body = World.CreateBody(bd);
body.CreateFixture(fd);
var gravity = 10.0f;
var I = body.Inertia;
var mass = body.Mass;
// For a circle: I = 0.5 * m * r * r ==> r = sqrt(2 * I / m)
var radius = (float)Math.Sqrt(2.0f * I / mass);
var jd = new FrictionJointDef();
jd.LocalAnchorA.SetZero();
jd.LocalAnchorB.SetZero();
jd.BodyA = ground;
jd.BodyB = body;
jd.CollideConnected = true;
jd.MaxForce = mass * gravity;
jd.MaxTorque = 0.1f * mass * radius * gravity;
World.CreateJoint(jd);
}
}
}
