Help Marquee tool

[Richard]

after you've determined which particles end up projected inside your marquee coordinates, then yes, you can make a handle out of them using the above code.

Currently, my code is below;

Code:

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

namespace Obi
{
   public class CreateHandle : MonoBehaviour
   {
       ObiActor actor;
       public ObiSolver solver;
       public Transform anchor;
       static protected Vector3[] wsPositions = new Vector3[0];
       static public bool[] selectionStatus = new bool[0];
       static int lastSelectedParticle = 0;
       //Selection related:
       static protected int selectedCount = 0;
       public static int SelectedParticleCount
       {
           get { return selectedCount; }
       }
       // Start is called before the first frame update
       void Start()
       {
           ObiSolver solver = actor.Solver;
           actor = GetComponent<ObiActor>();

           for (int i = 0; i < actor.positions.Length; ++i)
           {
               int indexInSolver = actor.particleIndices[i];
               Vector3 projectedPos = GetComponent<Camera>().WorldToScreenPoint(solver.positions[indexInSolver]);
               selectionStatus[i] = true;
           }

           // Create the handle:
           GameObject c = new GameObject("Obi Handle");
           Undo.RegisterCreatedObjectUndo(c, "Create Obi Particle Handle");
           ObiParticleHandle handle = c.AddComponent<ObiParticleHandle>();
           handle.Actor = actor;

           selectedCount = 0;
           for (int i = 0; i < selectionStatus.Length; i++)
           {
               if (actor.active[i] && selectionStatus[i])
               {
                   selectedCount++;
                   lastSelectedParticle = i;
               }
           }

           // Calculate position of handle from average of particle positions:
           Vector3 average = Vector3.zero;
           for (int i = 0; i < selectionStatus.Length; i++)
           {
               if (selectionStatus[i])
               {
                   average += wsPositions[i];
               }
           }

           c.transform.position = average / selectedCount;

           // Add the selected particles to the handle:
           for (int i = 0; i < selectionStatus.Length; i++)
           {
               if (selectionStatus[i])
               {
                   handle.AddParticle(i, wsPositions[i], actor.invMasses[i]);
               }
           }
       }


       // Update is called once per frame
       void Update()
       {

       }
   }
}

There are two errors.
・Obi Solver does not contain definition of "position"
(error CS1061: 'ObiSolver' does not contain a definition for 'positions' and no accessible extension method 'positions' accepting a first argument of type 'ObiSolver' could be found (are you missing a using directive or an assembly reference?))

・I cannot find out "Undo"
(error CS0103: The name 'Undo' does not exist in the current context)


Do you know how to fix this? Or are there other much problems here, or I should change code at a fundamental level?