/// <summary>
/// This method is called every cycle used to update the state of the <see cref="Node"/>.
/// </summary>
/// <param name="gameTime">The current game time.</param>
public virtual void Update(GameTime gameTime)
{
bool isDirtyThisFrame = IsDirty;
if (IsDirty)
{
// compute local transform
LocalTransform = Matrix2.CreateScale(Scale) *
Matrix2.CreateRotationZ(MathHelper.ToRadians(Rotation)) *
Matrix2.CreateTranslation(Position);
// compute world transform for this node
if (Parent != null)
{
// compute world transform
WorldTransform = LocalTransform * Parent.WorldTransform;
}
else
{
// no parent so WorldTransform and LocalTransform are equivalent.
WorldTransform = LocalTransform;
}
IsDirty = false;
}
// update children
foreach (Node child in Children)
{
if (isDirtyThisFrame)
{
child.IsDirty = true;
}
child.Update(gameTime);
}
}
