private void UpdateMouseBody()
{
if (cursorJoint == null)
{
return;
}
Vect mousePosition = cursorBody.Position;
Vect newPoint = mousePosition.Lerp(chipmunkDemoMouse, 0.25);
cursorBody.Velocity = (newPoint - mousePosition) * 60;
cursorBody.Position = newPoint;
}
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;
}