How can I get an NPC to move randomly in XNA? - random

Question

I basically want a character to walk in one direction for a while, stop, then go in another random direction. Right now my sprites look but don't move, randomly very quickly in all directions then wait and have another seizure. I will post the code I have so far in case that is useful.
class NPC: Mover
{
int movementTimer = 0;
public override Vector2 direction
{
get
{
Random rand = new Random();
int randDirection = rand.Next(8);
Vector2 inputDirection = Vector2.Zero;
if (movementTimer >= 50)
{
if (randDirection == 4)
{
inputDirection.X -= 1;
movingLeft = true;
}
else movingLeft = false;
if (randDirection == 1)
{
inputDirection.X += 1;
movingRight = true;
}
else movingRight = false;
if (randDirection == 2)
{
inputDirection.Y -= 1;
movingUp = true;
}
else movingUp = false;
if (randDirection == 3)
{
inputDirection.Y += 25;
movingDown = true;
}
else movingDown = false;
if (movementTimer >= 100)
{
movementTimer = 0;
}
}
return inputDirection * speed;
}
}
public NPC(Texture2D textureImage, Vector2 position,
Point frameSize, int collisionOffset, Point currentFrame, Point sheetSize,
Vector2 speed)
: base(textureImage, position, frameSize, collisionOffset, currentFrame,
sheetSize, speed)
{
}
public NPC(Texture2D textureImage, Vector2 position,
Point frameSize, int collisionOffset, Point currentFrame, Point sheetSize,
Vector2 speed, int millisecondsPerframe)
: base(textureImage, position, frameSize, collisionOffset, currentFrame,
sheetSize, speed, millisecondsPerframe)
{
}
public override void Update(GameTime gameTime, Rectangle clientBounds)
{
movementTimer++;
position += direction;
if (position.X < 0)
position.X = 0;
if (position.Y < 0)
position.Y = 0;
if (position.X > clientBounds.Width - frameSize.X)
position.X = clientBounds.Width - frameSize.X;
if (position.Y > clientBounds.Height - frameSize.Y)
position.Y = clientBounds.Height - frameSize.Y;
base.Update(gameTime, clientBounds);
}
}

Answer 1

How about you create a method to get a random direction:
Vector2 GetRandomDirection()
{
Random random = new Random();
int randomDirection = random.Next(8);
switch (randomDirection)
{
case 1:
return new Vector2(-1, 0);
case 2:
return new Vector2(1, 0);
case 3:
return new Vector2(0, -1);
case 4:
return new Vector2(0, 1);
//plus perhaps additional directions?
default:
return Vector2.Zero;
}
}
And then, when a set time has elapsed, you call that method to change the direction:
double totalElapsedSeconds = 0;
const double MovementChangeTimeSeconds = 2.0; //seconds
public override void Update(GameTime gameTime, Rectangle clientBounds)
{
totalElapsedSeconds += gameTime.ElapsedGameTime.TotalSeconds;
if (totalElapsedSeconds >= MovementChangeTimeSeconds)
{
totalElapsedSeconds -= MovementChangeTimeSeconds;
this.direction = GetRandomDirection();
}
position += direction;
//...
}
Use different code to detect which direction the NPC is moving (the booleans movingLeft, movingRight, etc.). Detect those values based on the direction vector. This way you don't have to assign redundant values.
enum MoveDirection
{
Up, Down, Left, Right, UpLeft, UpRight, DownLeft, DownRight, None
}
public MoveDirection GetMoveDirection(Vector2 direction)
{
if (direction.Y < 0)
{
if (direction.X < 0)
return MoveDirection.UpLeft;
else if (direction.X > 0)
return MoveDirection.UpRight;
else
return MoveDirection.Up;
}
else if (direction.Y > 0)
{
if (direction.X < 0)
return MoveDirection.DownLeft;
else if (direction.X > 0)
return MoveDirection.DownRight;
else
return MoveDirection.Down;
}
else
{
if (direction.X < 0)
return MoveDirection.Left;
else if (direction.X > 0)
return MoveDirection.Right;
else
return MoveDirection.None;
}
}
I presume this is used for rotating the sprite (or perhaps drawing a different one), so now you just need a switch:
public override void Draw(GameTime gameTime, SpriteBatch spriteBatch)
{
MoveDirection moveDirection = GetMoveDirection(this.direction);
switch(moveDirection)
{
case MoveDirection.Up:
//Draw up-facing sprite, or assign a value to a rotation variable.
break;
case MoveDirection.UpLeft:
//...
}
}

Answer 2

You can examine Platformer Starter Kit to know how enemies move.
As Microsoft discontinue the XNA development for Windows 8, he removes all links to download XNA 4 starter kits.
I upload original Platformer source code to bitbucket.
Here you can download original Platformer Starter Kit Source Code for XNA 4 http://vackup.blogspot.com.ar/2012/11/download-original-platformer-starter.html