private void ClipPoly(Polygon shape, Vect n, double distance)
{
Body body = shape.Body;
int count = shape.Count;
var clipped = new List <Vect>(count);
for (int i = 0, j = count - 1; i < count; j = i, i++)
{
Vect a = body.LocalToWorld(shape.GetVertex(j));
double a_dist = a.Dot(n) - distance;
if (a_dist < 0.0)
{
clipped.Add(a);
}
Vect b = body.LocalToWorld(shape.GetVertex(i));
double b_dist = b.Dot(n) - distance;
if (a_dist * b_dist < 0.0)
{
double t = Math.Abs(a_dist) / (Math.Abs(a_dist) + Math.Abs(b_dist));
clipped.Add(a.Lerp(b, t));
}
}
Vect centroid = Polygon.CentroidForPoly(clipped);
double mass = Polygon.AreaForPoly(clipped, 0.0f) * Density;
double moment = Polygon.MomentForPolygon(mass, clipped, -centroid, 0.0f);
var new_body = new Body(mass, moment);
space.AddBody(new_body);
new_body.Position = centroid;
new_body.Velocity = body.GetVelocityAtWorldPoint(centroid);
new_body.AngularVelocity = body.AngularVelocity;
var transform = Transform.CreateTranslation(-centroid);
Shape new_shape = new Polygon(new_body, clipped, transform, 0.0);
space.AddShape(new_shape);
new_shape.Friction = shape.Friction;
}
public override void Update(double dt)
{
// turn the control body based on the angle relative to the actual body
Vect mouseDelta = ChipmunkDemoGame.ChipmunkDemoMouse - tankBody.Position;
double turn = tankBody.Rotation.Unrotate(mouseDelta).ToAngle();
tankControlBody.Angle = tankBody.Angle - turn;
// drive the tank towards the mouse
if (ChipmunkDemoGame.ChipmunkDemoMouse.Near(tankBody.Position, 30.0))
{
tankControlBody.Velocity = Vect.Zero;
}
else
{
double direction = mouseDelta.Dot(tankBody.Rotation) > 0.0 ? 1.0 : -1.0;
tankControlBody.Velocity = tankBody.Rotation.Rotate(new Vect(30.0 * direction, 0.0f));
}
base.Update(dt);
}
private void SliceShapePostStep(Space space, object s, object c)
{
var context = (SliceContext)c;
var shape = (Polygon)s;
Vect a = context.A;
Vect b = context.B;
// Clipping plane normal and distance.
Vect diff = b - a;
Vect n = diff.Perpendicurlar.Normalize();
double dist = a.Dot(n);
ClipPoly(shape, n, dist);
ClipPoly(shape, -n, -dist);
Body body = shape.Body;
space.RemoveShape(shape);
space.RemoveBody(body);
shape.Free();
body.Free();
}