Train along track,need to calculate perpendicular direction

This relates to the train problem I have. It is frustrating I know it is about vectors but I just can't get it.

So I have a simulation a cube with translation along forward direction I have a ray cast to the right (90 degrees to the direction of travel I have a rail track to the right not perpendicular to the translating box I have calculated the hit.point hit.normal The hit.normal is being shown with the draw ray it is perpendicular to the track

To make sure the cube follows the track all I need to do is find the vector perpendicular to the hit.normal and apply this normal to the cubes transform.direction

Any help would appreciated.
The attachment has simple simulator
cube represents train/carriages
green ray -represents forward vector
blue ray -represents hit.normal

 

I haven't looked at the project, but finding the perpendicular vector should be straightforward:

Code (csharp):

1. Vector3 perp = Vector3.Cross(hit.normal, Vector3.up);

Note that this perpendicular vector may not coincide with the direction you want the train to move in.

If you want to get that particular vector, project the move direction onto the perp vector:

Code (csharp):

1. Vector3 targetDir = Vector3.Project(transform.forward, perp).normalized;

As long as the angle between track and train are not too far off (i.e. a 90 degree difference), that should get you the perpendicular vector in the right direction.

 

I sort of get it
but do I take the Vector3 targetDir
and apply it as a

direction = transform.TransformDirection(targetDir);

 

http://forum.unity3d.com/viewtopic.php?t=48619&highlight=train+track

this links to other post with diagrams to show what I am trying to achieve

It is for a game level involving a train carriages I need train driven with velocity and not animation
An ability to alter track(signals) and slow down carriages to alter arrangement to solve game puzzle.

 

I have a screenshot of top down view

box represents train/carriages to the right is the rail track
the blue line is the hit normal and the green line is the vector from the resulting dot product of hit normal and up
What I need is the box blue facing direction to change to the green perpendicular
line direction

any ideas

 

The vectors from my example were all in world space, so they should not need any modification.

To align your blue vector with the green one use:

Code (csharp):

1.  
2. transform.forward = greenVector;

Basically transform.forward is the blue vector and can be assigned to directly.

 

Thank you very much,indeed!

The box is following the track nicely!!

at the moment it jumps per section of track anyway of interpolating different vectors so I can a smooth rotation?

I noticed another problem as the train goes from section to section it gets closer to track and eventually gets snagged any chance of solving it?

 

You can do smooth rotations like this:

Code (csharp):

1. transform.forward = Vector3.Slerp(transform.forward, greenVector, Time.deltaTime * turnSpeed);

turnSpeed is a float that influences how quickly the train will align with the new vector.

Your raycast should give you the actual distance to the hit. If this value deviates from the desired distance to the track, you could use the distance, the hit normal and the Transform.Translate() function to slowly move the train back to the right distance from the track.

 

I have fixed the issue with the train moving closer to the rail section

I made vector = hit.pos +hit.normal * 2
this vector was added to transfrom.position of train

still need some way of interpolating change from one vector to another?

 

I posted the code in new post instead of reply
I see the slerp command but I cannot figure where it goes I already have
transform.forward = perp;
I am very grateful for your help so far
CODE BELOW

var turnSpeed: float;



function FixedUpdate(){
//cast ray from train to track
direction2 = transform.TransformDirection(Vector3.right);
var hit: RaycastHit ;
if(Physics.Raycast (transform.position,direction2,hit,30)){
if( hit.collider.gameObject.tag =="track") {


// determines distance of train from track
var Vfromtrack : Vector3;
Vfromtrack = hit.point + hit.normal*3;

Debug.DrawRay (hit.point,hit.normal*1, Color.blue);

//dot product of two vectors to find perpendicular vector
var perp: Vector3;
perp = Vector3.Cross(Vector3.up,hit.normal);

transform.forward = Vector3.Slerp(transform.forward, perp, Time.deltaTime * turnSpeed);
//this gives train new direction!!!!!
transform.forward = perp;
//this fixes position of train so it is always a certain distance from track
transform.position = Vfromtrack;


//this moves train
this.rigidbody.velocity = transform.forward * 1;


//to show visual vector for perp
Debug.DrawRay (transform.position, perp, Color.black);
}
}

}

 

It replaces that line.

 

I have replaced the line
and it is moving along but when it gets to the next track segment it jitters and get stuck
if I increase turn speed this sometimes works?

 

There is an (apparently problematic) dependency between transform.forward and your
transform.TransformDirection(Vector3.right); line (note that you can also use transform.right instead of that mouthful . they are equivalent).

To remove that dependency, you could store your perp Vector3 in the class and use:

Code (csharp):

1. direction2 = Vector3.Cross(perp, Vector3.up);

Instead of the current "direction2 =" line. This will make your track detector raycast ignore the animation of the turn.

 

Still having problem with train jitter after adding line.
Any ideas.

Code (csharp):

1.  
2. var turnSpeed: float;
3. var trainSpeed: float;
4.  
5.  
6. function FixedUpdate(){
7.  
8.  
9.  
10. var hit: RaycastHit ;
11. if(Physics.Raycast (transform.position,transform.right,hit,10)){
12. if( hit.collider.gameObject.tag =="track") {
13.    
14. //dot product of two vectors to find perpendicular vector  
15. var perp: Vector3;
16. perp = Vector3.Cross(Vector3.up,hit.normal);
17.  
18. //dot product of two vectors to find
19. direction2 = Vector3.Cross(perp, Vector3.up);
20.                
21. // determines distance of train from track
22. var Vfromtrack : Vector3;
23. Vfromtrack = hit.point + hit.normal*2;
24. //this fixes position of train so it is always a certain distance from track
25. transform.position = Vfromtrack;
26.            
27. Debug.DrawRay (hit.point,hit.normal*1, Color.blue);
28.  
29.  
30. //this gives train new direction!!!!!
31. transform.forward = Vector3.Slerp(transform.forward, [b]perp, Time.deltaTime * turnSpeed);[/b]
32.  
33. //this moves train
34. this.rigidbody.velocity = transform.forward * trainSpeed;
35.    
36.  
37. //to show visual vector for perp
38. Debug.DrawRay (transform.position, perp, Color.black); 
39. }
40. }          
41.    
42. }
43.  

also when the train encounters left bend the train speeds up?