Unity3D: Bouncing/Reflecting Raycast

Question

Hey everyone thanks for the help,

What I am trying to do is fairly straight forward, I am trying to display a Line Renderer that follows my bouncing/reflecting Raycast.

Here is what I have so far.

 private LineRenderer lr;

public int maxReflectionCount = 3;
public float maxStepDistance = 200f;


void Start()
{
    lr = GetComponent<LineRenderer>();
}


void Update()
{
    RaycastHit hit;

    if (Physics.Raycast(transform.position, transform.forward, out hit))
    {
        if (hit.collider)
        {
            lr.SetPosition(1, new Vector3(0, 0, hit.distance));

            Reflect(this.transform.position + this.transform.forward * 0.75f, this.transform.forward, maxReflectionCount);


        }
    }
    else
    {
        lr.SetPosition(1, new Vector3(0, 0, 2000));

    }

}


private void Reflect(Vector3 position, Vector3 direction, int reflectionsRemaining)
{

    if (reflectionsRemaining == 0)
    {
        return;
    }


    Vector3 startingPosition = position;


    Ray ray = new Ray(position, direction);
    RaycastHit hit2;
    if (Physics.Raycast(ray, out hit2, maxStepDistance))
    {
        direction = Vector3.Reflect(direction, hit2.normal);
        position = hit2.point;
    }
    else
    {
        position += direction * maxStepDistance;
    }



    Debug.DrawRay(startingPosition, position, Color.green);


    Reflect(position, direction, reflectionsRemaining - 1);


}

It seems like Vector3.Reflect is the key but I can't quite figure out how to use it properly.

I have gotten it to sort of work with Gizmos

but I cant use Gizmos in the real thing and I am having trouble getting it to work with the LineRenderer. I have even tried to use the Debug.DrawRay but to no avail.

I really just want to use it to show what angles things will bounce around at. Any ideas on how I might get this working?

I appreciate any help!

EDIT 1: So I have removed all the Line Renderer stuff because I can worry about that later and I been working on what Hacky suggested. I still cant get it working properly, but here is what it currently looks like.

//private LineRenderer lr;

public int maxReflectionCount = 3;
public float maxStepDistance = 200f;

Vector3 reflDirection;
Vector3 hitPosition;


void Start()
{
    //lr = GetComponent<LineRenderer>();
}


void Update()
{
    RaycastHit hit;

    if (Physics.Raycast(transform.position, transform.forward, out hit))
    {
        if (hit.collider)
        {
            //lr.SetPosition(1, new Vector3(0, 0, hit.distance));

            Reflect(this.transform.position + this.transform.forward * 0.75f, this.transform.forward, maxReflectionCount);
        }
    }
    else
    {
        //lr.SetPosition(1, new Vector3(0, 0, 2000));
    }

}


private void Reflect(Vector3 position, Vector3 direction, int reflectionsRemaining)
{

    if (reflectionsRemaining == 0)
    {
        return;
    }


    Vector3 startingPosition = position;


    Ray ray = new Ray(position, direction);
    RaycastHit hit2;
    if (Physics.Raycast(ray, out hit2, maxStepDistance))
    {
        reflDirection = Vector3.Reflect(direction, hit2.normal);
        hitPosition = hit2.point;
    }
    else
    {
        position += reflDirection * maxStepDistance;
    }

    Debug.DrawRay(startingPosition, reflDirection, Color.green, 1);

    //Debug.DrawLine(startingPosition, position, Color.blue);


    Reflect(position, direction, reflectionsRemaining - 1);

}

EDIT 2 (Big Progress!): Ok so I got the Raycasting Reflection working....and its glorious.

Here is what it looks like:

 public int maxReflectionCount = 5;
public float maxStepDistance = 200f;



void Start()
{


}


void Update()
{

    Laser();
}


void Laser()
{
    DrawReflectionPattern(this.transform.position + this.transform.forward * 0.75f, this.transform.forward, maxReflectionCount);
}

private void DrawReflectionPattern(Vector3 position, Vector3 direction, int reflectionsRemaining)
{
    if (reflectionsRemaining == 0)
    {
        return;
    }

    Vector3 startingPosition = position;

    Ray ray = new Ray(position, direction);
    RaycastHit hit;
    if (Physics.Raycast(ray, out hit, maxStepDistance))
    {
        direction = Vector3.Reflect(direction, hit.normal);
        position = hit.point;
    }
    else
    {
        position += direction * maxStepDistance;
    }

    //Gizmos.color = Color.yellow;
    //Gizmos.DrawLine(startingPosition, position);

    Debug.DrawLine(startingPosition, position, Color.blue);

    DrawReflectionPattern(position, direction, reflectionsRemaining - 1);


}

Now I just have to figure out how to connect the Line Renderer to it and we are in business!

Hacky Hacky · Accepted Answer · 2018-08-20T15:11:29

I read 2 questions:

I don't know how to use vector3.reflect ("It seems like Vector3.Reflect is the key but I can't quite figure out how to use it properly.")
I don't know how to use the linerenderer ("I am having trouble getting it to work with the LineRenderer")

I'll try answering these questions here: The way you use Vector3.Reflect is correct. See the sample in the unity docs: https://docs.unity3d.com/ScriptReference/RaycastHit-normal.html

First visualize the outcome of the equation with Debug.DrawRay(start,dir,color, duration) or Debug.drawline. Use a duration of 1 so that it stays visible in the scene for a second and doesn't disappear immediately. In your Debug.DrawRay is an error: The second parameter of Debug.DrawRay is the direction where you have the position. You also don't save the start position of the ray so it should be:

Ray ray = new Ray(position, direction);
RaycastHit hit2;
if (Physics.Raycast(ray, out hit2, maxStepDistance))
{
    reflDirection = Vector3.Reflect(direction, hit2.normal);
    hitPosition = hit2.point;
}
else
{
    position += reflDirection * maxStepDistance;
}

Debug.DrawRay(hitPosition, reflDirection, Color.green);

When that works, use the linerenderer to show it in the game view. It expects only positions, so no directions. Be careful to not mix directions with positions. (add a direction to a position to get the destination)

Unity3D: Bouncing/Reflecting Raycast

1 Answers