How to use ray plane intersection & update point vector 3?

Question

I want to use a ray like a line and update the end point vector 3 when a plane intersects the ray.

Is it possible to make a new point from the ray intersection and change it if the plane intersects?

Ray.GetPoint is not changing with each update.

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class PlaneCast : MonoBehaviour
 {
     public Ray r;
 
     public Vector3 P3;
 
     public GameObject PointA;
 
     public GameObject PointB;
 
     public Plane quadPlane;
 
     public float LineDistance;
 
     // Start is called before the first frame update
     void Start()
     {
         P3 = new Vector3();
 
         quadPlane = new Plane();
 
         Mesh mesh = GetComponent<MeshFilter>().sharedMesh;
 
         Vector3[] normals = mesh.normals;
 
         quadPlane.SetNormalAndPosition(transform.TransformDirection(normals[0]), transform.position);
     }
     
     // Update is called once per frame
     void Update()
     {
         Vector3 P1 = PointA.transform.position;
 
         Vector3 P2 = PointB.transform.position;
 
         Vector3 tp1 = transform.TransformPoint(P1);
 
         Vector3 tp2 = transform.TransformPoint(P2);
 
         Debug.DrawLine(P1, P2);
 
         r = new Ray(tp1, tp2);
 
         //LineDistance = Vector3.Distance(tp1, tp2);
 
         if (quadPlane.Raycast(r, out LineDistance))
         {
             print(r.GetPoint(LineDistance));
             Debug.Log("Intersecting plane");
         }
      
         P3 = r.GetPoint(LineDistance);
         Debug.Log(LineDistance);
     }
 }

Answer 1

Best Answer

Answer by Bunny83 · Aug 14, 2022 at 03:00 PM

Well, first of all the way you create the Ray struct is already flawed. Have a look at the constructor. It does not take two points but one point (the origin of the ray) and a direction vector. You currently pass your second point as direction vector. You probably want to pass tp2 -tp1 as direction.

As for the rest of your code, using LineDistance outside the if statement has issues if the ray doesn't hit anything. Since you use an infinite plane it shouldn't be a huge issue, but generally a flawed approach.

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Answer 2

The ray is infinite in one direction.

I'm wanting to use ray plane intersection like line plane intersection.

I changed the if statement to check the distance to the line.

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class RayPlaneIntersection : MonoBehaviour
 {
     public Ray r;
 
     public GameObject PointA;
 
     public GameObject PointB;
 
     public float MaxDistance;
 
     public float LineDistance;
 
     public Vector3 IntersectionPoint;
 
     public GameObject PlaneGameObject;
 
     // Start is called before the first frame update
     void Start()
     {
         
     }
 
     // Update is called once per frame
     void Update()
     {
         Vector3 P1 = PointA.transform.position;
 
         Vector3 P2 = PointB.transform.position;
 
         Debug.DrawRay(P1, P2 - P1, Color.blue);
 
         r = new Ray(P1, P2 - P1);
 
         MaxDistance = Vector3.Distance(P1, P2);
 
         PlaneGameObject.GetComponent<PlaneObject>().ObjectPlane.Raycast(r, out LineDistance);
 
         if (LineDistance >= 0 && LineDistance <= MaxDistance)
         {
             IntersectionPoint = r.GetPoint(LineDistance);
             print(r.GetPoint(LineDistance));
             Debug.Log("Intersecting line");
         }
     }
 }

How to use ray plane intersection & update point vector 3?

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