Game Physics - Learning C# by Programming Games - page 359

calculated as

distance.X . Why? Because there is a collision, the
distance between the two rectangles is smaller than minDistance . And because
distance is negative, the expression −

−

minDistance.X

−

distance.X gives the difference
between the two as a negative value. If distance was positive, then the expression
minDistance.X

− minDistance.X

− distance.X gives the positive difference between the two. The same
reasoning holds for the y distance. We can then calculate the depth as follows:

Vector2 depth = Vector2.Zero;
if (distance.X > 0)
depth.X = minDistance.X

− distance.X;

else
depth.X =

−

minDistance.X

−

distance.X;

if (distance.Y > 0)
depth.Y = minDistance.Y

−

distance.Y;

else
depth.Y = − minDistance.Y − distance.Y;

Finally, we return the depth vector as the final result of this method.

return depth;

When we know that the character collides with the tile, we calculate the intersec-
tion depth using the method that we just added to the Collision class:

Vector2 depth = Collision.CalculateIntersectionDepth(boundingBox, tileBounds);

Now that we have calculated the intersection depth, there are two ways to solve
this collision: move the character in the x -direction, or move the character in the
y -direction. Generally, we want to move the character the least possible distance to
avoid unnatural motions or displacements. So, if the x depth is smaller than the y
depth, we will move the character in the x direction, otherwise in the y direction. We
can check this with an if -instruction. When comparing the two depth dimensions, we
have to take into account that they might be negative. We solve this by comparing
the absolute values:

if (Math.Abs(depth.X) < Math.Abs(depth.Y))
{

movecharacterinthexdirection

}

Do we always want to move the player if there is a collision with a tile? Well,
that depends on the tile type. Remember that the enumerated type TileType is
used to represent three possible tile types: TileType.Background , TileType.Normal , and
TileType.Platform . If the tile that we are colliding with is a background tile, we defi-
nitely do not want to move the player. Also, in the case of moving in the x -direction,