Raycasting to Steer - Help?

Unity Engine
1

For one of my classes that I’m taking, we have to use steering forces to move Hunters and Prey around a map, for the Hunter(s) to chase the nearest prey, and to take into account the bounds of the map (walls) and when nearby, steer away from them. I previously made this assignment work in Flash (it was what was originally assigned), and am trying to convert the project for implementation in Unity (because I love C#, and want to help people [including myself] understand the concepts in a different environment). I’m trying to predict where my hunters/prey are one or more timesteps in the future (the have kinematic rigidbody colliders) using raycasts; I thought it might be logical to do it that way, but I could be wrong (basically trying to a projection of a point by a foward vector akin to a HitTestPoint).

Without getting into “too much” Unity specific things (i.e. leaning on the physics engine to do things versus writing my own code [for practice]), I thought this would work:

protected Vector3 StayOnStage()
	{
		//Look in front of self - is something there?
		RaycastHit hitDetected = new RaycastHit();
		if(Physics.Raycast(this.transform.position, forwardVect,out hitDetected, 2f))
		{
			if(hitDetected.transform.tag =="SideWall"||hitDetected.transform.tag =="VerticalWall")
				return Flee(hitDetected.transform.position);
			else
				return Vector3.zero;
		}
		else
			return Vector3.zero;
	}

The returned Vector3 is added to the forward vector in another method, which calculates the final forward vector as a sum of all forces (seeking, fleeing, dodging, etc.). However, I can’t tell why my objects are now flying out of the bounds of the map using this specific code. If it helps, Flee looks like this:

protected Vector3 Flee(Vector3 targetPos)
	{
		// Set desiredVelocity equal to a vector AWAY from targPos
		Vector3 desVel;
		Vector3 steeringForce;
		desVel = targetPos+transform.position;//subtracting creates a vector TOWARDS the target
		// scale desired velocity so its magnitude equals max speed
		desVel.Normalize();
		desVel *= maxSpeed;
		// to get steeringForce subtract current velocity from desired velocity
		steeringForce = desVel - velocity;//velocity being an intervariable which is equal to the forward vector * speed
		return steeringForce;
	}

Any thoughts on what I did wrong? I’ll eventually be going back through to trim out extraneous things (ex. the use of velocity as a variable, probably), but am I approaching this properly using raycasts, or should I be using something else?

Thank you for your time and patience :slight_smile:

2

Woops, forgot I’m to ask this stuff in Unity Answers. I’d appreciate if this was deleted :stuck_out_tongue:

3

You can ask in either place, is fine - unless you have to ask for a class reason or something.

I see “desVel = targetPos + transform.position”; should be subtraction. :slight_smile:

4

Well, our class is loosely based on this: http://www.red3d.com/cwr/steer/gdc99/

Also, thanks for letting me know about the Forum vs Answers - nothing really said not to post here, just didn’t want to cause problems.

To the meat of things I guess:
I though with Seeking an item, we want to get the difference between where we are and where we want to be and use the resultant to go that way, whereas with seeking we add instead of subtract to get distance between us and the thing we wish to avoid? (I made the change, I’m just confused since now my Flee is my Seek… or is it that they SHOULD be the same, and I merely subtract versus add at the force calculation step?)

Also, the rays still hate me, and like to bog the game down even in a fixed update… is Collider.Raycast “better” for this then?

5 
desVel = transform.position- targetPos;

Was that what you meant? Just realized my ordering for that was wrong.