Game Development Reference
In-Depth Information
In addition, we change the position of the object that was changed from being the
leftmost object to the rightmost object. The result of this positional change is a nice
motion effect, as we will see later on. The method
ShiftRowRight
is quite similar to
this method, have a look for yourself.
We also want to add a method that gives us the anchor position in the grid for
any game object. This method is going to be useful later on. As a parameter, this
method expects a game object, and it returns a
Vector2
object containing the anchor
position. Here is the complete method:
public
Vector2 GetAnchorPosition(GameObject s)
{
for
(
int
x = 0; x < Columns; x++)
for
(
int
y=0;y<Rows;y++)
if
(grid[x, y] == s)
return new
Vector2(x
∗
cellWidth, y
∗
cellHeight);
return
Vector2.Zero;
}
This method uses (again) a nested
for
-instruction to look for the game object that
was passed as a parameter. Once this object has been found, we calculate its anchor
position based on the
x
and
y
indices in the grid, together with the cell size. If the
object was not found, we return the zero vector (
Vector2.Zero
). Since this method is
useful for almost all grids, we added this method to the
GameObjectGrid
class.
Because the
GameObjectGrid
class inherits from
GameObject
, we need to define
what the different game loop methods do. In this case, it is quite straightforward.
The nice thing in C# is that we can actually use
foreach
on arrays as well, even if
they are multidimensional. So, for instance the
Update
method becomes
public override void
Update(GameTime gameTime)
{
foreach
(GameObject obj
in
grid)
obj.Update(gameTime);
}
Both the
HandleInput
method and the
Draw
method do something very similar. Note
that when drawing the objects in a grid, we do not take the drawing layer of each
game object into account, to keep things simple. Can you extend the
Draw
method
of this class so that it does take care of it? Hint: copy the game objects from the grid
to a list, and add them in the same fashion as we did in the
GameObjectList
class.
14.4.5 Moving Smoothly on the Grid
For our objects to move smoothly on the grid, we are going to use the
velocity
and
the
position
member variables that are a part of the
GameObject
class. We are going
