ClippableObject.cs

using UnityEngine;
public class ClippableObject : MonoBehaviour
{
    //only 3 clip planes for now, will need to modify the shader for more.
    private int _clipPlanes = 4;

    public Material[] _materials;

    public GameObject _planeX;
    public GameObject _planeXnegative;
    public GameObject _planeY;
    public GameObject _planeZ;    

    public void Update()
    {

        Vector3 positionX   = _planeX.transform.position;
        Vector3 normalX     = _planeX.transform.up;

        Vector3 positionY   = _planeY.transform.position;
        Vector3 normalY     = _planeY.transform.up;

        Vector3 positionZ   = _planeZ.transform.position;
        Vector3 normalZ     = _planeZ.transform.up;

        Vector3 positionXnegative = _planeXnegative.transform.position;
        Vector3 normalXnegative = _planeXnegative.transform.up;

        if ( _materials != null )
        {
            for ( int i = 0; i < _materials.Length; i++ )
            {
                if ( _materials[i] == null )
                {
                    continue;
                }
                switch ( _clipPlanes )
                {
                    case 0:
                        //https://docs.unity3d.com/ScriptReference/Material.EnableKeyword.html
                        _materials[i].DisableKeyword( "CLIP_ONE" );
                        _materials[i].DisableKeyword( "CLIP_TWO" );
                        _materials[i].DisableKeyword( "CLIP_THREE" );
                        _materials[i].DisableKeyword( "CLIP_FOUR" );
                        break;
                    case 1:
                        _materials[i].EnableKeyword( "CLIP_ONE" );
                        _materials[i].DisableKeyword( "CLIP_TWO" );
                        _materials[i].DisableKeyword( "CLIP_THREE" );
                        _materials[i].DisableKeyword( "CLIP_FOUR" );
                        break;
                    case 2:
                        _materials[i].DisableKeyword( "CLIP_ONE" );
                        _materials[i].EnableKeyword( "CLIP_TWO" );
                        _materials[i].DisableKeyword( "CLIP_THREE" );
                        _materials[i].DisableKeyword( "CLIP_FOUR" );
                        break;
                    case 3:
                        _materials[i].DisableKeyword( "CLIP_ONE" );
                        _materials[i].DisableKeyword( "CLIP_TWO" );
                        _materials[i].EnableKeyword( "CLIP_THREE" );
                        _materials[i].DisableKeyword( "CLIP_FOUR" );
                        break;
                    case 4:
                        _materials[i].DisableKeyword( "CLIP_ONE" );
                        _materials[i].DisableKeyword( "CLIP_TWO" );
                        _materials[i].DisableKeyword( "CLIP_ THREE" );
                        _materials[i].EnableKeyword( "CLIP_FOUR" );
                        break;
                }

                //Pasa los planos al shader si es necesario.
                if ( _clipPlanes >= 1 )
                {
                    _materials[i].SetVector( "_planePos", positionX );
                    //plano vector normal es el vector 'arriba' girado.
                    _materials[i].SetVector( "_planeNorm", normalX );
                }

                if ( _clipPlanes >= 2 )
                {
                    _materials[i].SetVector( "_planePos2", positionY );
                    _materials[i].SetVector( "_planeNorm2", normalY );
                }

                if ( _clipPlanes >= 3 )
                {
                    _materials[i].SetVector( "_planePos3", positionZ );
                    _materials[i].SetVector( "_planeNorm3", normalZ );
                }
                if ( _clipPlanes >= 4 )
                {
                    _materials[i].SetVector( "_planePos4", positionXnegative );
                    _materials[i].SetVector( "_planeNorm4", normalXnegative );
                }
            }
        }
    }
}