public static Vector2 OnscreenDirection(Rectangle extent, BoundingCircle bounds)
{
// Calculate the normalized vector from current position to onscreen position.
Vector2 onScreenPosition = RandomOnscreenPosition(extent, bounds);
Vector2 direction = onScreenPosition - bounds.Position;
direction.Normalize();
return direction;
}
public void DrawBoundingCircle(SpriteBatch spriteBatch, BoundingCircle circle)
{
Rectangle textureBounds = _BoundingCircleTexture.Bounds;
Vector2 origin = new Vector2(textureBounds.Width / 2, textureBounds.Height / 2);
float scale = (circle.Radius * 2.0f) / _BoundingCircleTexture.Width;
spriteBatch.Draw(_BoundingCircleTexture, circle.Position, textureBounds,
Color.White, 0, origin, scale, SpriteEffects.None, 1.0f);
}
public static bool IsOffscreen(Rectangle extent, BoundingCircle bounds)
{
// Offscreen if closest point on extent is > radius distance away.
AABB extentAABB = new AABB(new Vector2(extent.Left, extent.Top),
new Vector2(extent.Right, extent.Bottom));
Vector2 closestPoint = extentAABB.ClosestPointTo(bounds.Position);
Vector2 displacement = closestPoint - bounds.Position;
return displacement.LengthSquared() > bounds.Radius * bounds.Radius;
}
public static bool IsOnscreen(Rectangle extent, BoundingCircle bounds)
{
float left = extent.Left + bounds.Radius;
float right = extent.Right - bounds.Radius;
float bottom = extent.Bottom - bounds.Radius;
float top = extent.Top + bounds.Radius;
Vector2 position = bounds.Position;
return left <= position.X && position.X <= right &&
top <= position.Y && position.Y <= bottom;
}
public static Vector2 RandomOffscreenPosition(Rectangle extent, BoundingCircle bounds)
{
// Choose a fully onscreen position.
Vector2 onScreenPosition = RandomOnscreenPosition(extent, bounds);
// Choose an offset to an offscreen position, randomly.
float[] xOffsets = {-extent.Width, 0, extent.Width};
float[] yOffsets = {-extent.Height, 0, extent.Height};
Vector2 offset;
do
{
offset = new Vector2(xOffsets[_Random.Next(3)], yOffsets[_Random.Next(3)]);
}
while (offset == Vector2.Zero);
return onScreenPosition + offset;
}
public static Vector2 RandomJustOffscreenPosition(Rectangle extent, BoundingCircle bounds)
{
Vector2 position = Vector2.Zero;
float diameter = 2 * bounds.Radius + 10;
int random1 = _Random.Next(2);
int random2 = _Random.Next(2);
if (random1 == 0)
{
// Make position offscreen from left/right.
position.X = extent.Left - diameter + random2 * (extent.Width + 2 * diameter);
position.Y = _Random.NextFloat(extent.Top - diameter, extent.Bottom + diameter);
}
else
{
// Make position offscreen from top/bottom.
position.X = _Random.NextFloat(extent.Left - diameter, extent.Right + diameter);
position.Y = extent.Top - diameter + random2 * (extent.Height + 2 * diameter);
}
return position;
}
public static Vector2 RandomOnscreenPosition(Rectangle extent, BoundingCircle bounds)
{
float left = extent.Left + bounds.Radius;
float right = extent.Right - bounds.Radius;
float bottom = extent.Bottom - bounds.Radius;
float top = extent.Top + bounds.Radius;
return new Vector2(_Random.NextFloat(left, right), _Random.NextFloat(top, bottom));
}
public bool IntersectsCircle(BoundingCircle circle)
{
Vector2 closestPoint = ClosestPointTo(circle.Position);
return Vector2.DistanceSquared(closestPoint, circle.Position) < circle.Radius * circle.Radius;
}
public bool Intersects(BoundingCircle other)
{
Vector2 d = Position - other.Position;
float r = Radius + other.Radius;
return d.LengthSquared() < r * r;
}
