Splice mesh by plane - unity3d

Question

I try splice mesh by intersect plane, but get wrong result.
my code (I slice mesh by plane with calc side from plane positive or negative and create accordingly place vertics in separte arrays (for negative and positive), if triangle belong to both side, then I calc intersections points and build new triangles:
public void SliceIt()
{
Mesh mesh = GetComponent<MeshFilter>().sharedMesh;
gameObject.name = "v1";
Vector3[] vertices = mesh.vertices;
Mesh cutplanemesh = cutplane.GetComponent<MeshFilter>().sharedMesh;
Vector3[] cutplanevertices = cutplanemesh.vertices;
p1 = cutplane.TransformPoint(cutplanevertices[40]);
p2 = cutplane.TransformPoint(cutplanevertices[20]);
p3 = cutplane.TransformPoint(cutplanevertices[0]);
var myplane = new Plane(p1, p2, p3);
Vector3[] vertics = mesh.vertices;
int[] triangles = mesh.triangles;
var side = new bool[vertics.Length];
for (var i = vertics.Length - 1; i >= 0; i--)
{
vertics[i] = transform.TransformPoint(vertics[i]);
side[i] = myplane.GetSide((vertics[i]));
}
var verticsPositive = new List<Vector3>();
var verticsNegative = new List<Vector3>();
var trianglesPositive = new List<int>();
var trianglesNegative = new List<int>();
for (var trix = triangles.Length - 3; trix >= 0; trix -= 3)
{
var index0 = triangles[trix];
var index1 = triangles[trix + 1];
var index2 = triangles[trix + 2];
var point0 = vertics[index0];
var point1 = vertics[index1];
var point2 = vertics[index2];
Debug.Log(point0 + " " + point1 + " " + point2);
if (side[index1] != side[index2] || side[index0] != side[index1] || side[index2] != side[index0])
{
if (side[index0] == side[index1])
Intersect(point0, point1, point2, myplane, side[index0], verticsPositive, verticsNegative, trianglesPositive, trianglesNegative);
else if (side[index0] == side[index2])
Intersect(point0, point2, point1, myplane, side[index0], verticsPositive, verticsNegative, trianglesPositive, trianglesNegative);
else if (side[index1] == side[index2])
Intersect(point1, point2, point0, myplane, side[index1], verticsPositive, verticsNegative, trianglesPositive, trianglesNegative);
}
else
{
if (side[index1])
{
trianglesPositive.Add(verticsPositive.Count + 2);
trianglesPositive.Add(verticsPositive.Count + 1);
trianglesPositive.Add(verticsPositive.Count + 0);
verticsPositive.Add(point2);
verticsPositive.Add(point1);
verticsPositive.Add(point0);
}
else
{
trianglesNegative.Add(verticsNegative.Count + 2);
trianglesNegative.Add(verticsNegative.Count + 1);
trianglesNegative.Add(verticsNegative.Count + 0);
verticsNegative.Add(point2);
verticsNegative.Add(point1);
verticsNegative.Add(point0);
}
}
}
var go1 = new GameObject();
go1.name = "positive";
var meshFilter = go1.AddComponent<MeshFilter>();
go1.AddComponent<MeshRenderer>();
var meshPositive = new Mesh();
meshPositive.vertices = verticsPositive.ToArray();
meshPositive.triangles = trianglesPositive.ToArray();
meshPositive.RecalculateBounds();
meshPositive.RecalculateNormals();
meshFilter.sharedMesh = meshPositive;
var go2 = new GameObject();
go2.name = "negative";
var meshFilter2 = go2.AddComponent<MeshFilter>();
go2.AddComponent<MeshRenderer>();
var meshNegative = new Mesh();
meshNegative.vertices = verticsNegative.ToArray();
meshNegative.triangles = trianglesNegative.ToArray();
meshNegative.RecalculateBounds();
meshNegative.RecalculateNormals();
meshFilter2.sharedMesh = meshNegative;
}
public void Intersect(Vector3 point0, Vector3 point1, Vector3 point2, Plane myplane, bool side, List<Vector3> verticsPositive, List<Vector3> verticsNegative, List<int> trianglesPositive,
List<int> trianglesNegative)
{
Vector3 pointIntersection1 = Vector3.zero;
var vector1 = point2 - point0;
var isIntersect1 = Math3d.LinePlaneIntersection(out pointIntersection1, point0, vector1, myplane.normal, p1);
Debug.Log("isIntersect " + isIntersect1 + " pointIntersection" + pointIntersection1);
Vector3 pointIntersection2 = Vector3.zero;
var vector2 = point2 - point1;
var isIntersect2 = Math3d.LinePlaneIntersection(out pointIntersection2, point1, vector2, myplane.normal, p1);
Debug.Log("isIntersect2 " + isIntersect1 + " pointIntersection2" + pointIntersection1);
if (side)
{
trianglesPositive.Add(verticsPositive.Count);
trianglesPositive.Add(verticsPositive.Count + 1);
trianglesPositive.Add(verticsPositive.Count + 2);
verticsPositive.Add(point0);
verticsPositive.Add(point1);
verticsPositive.Add(pointIntersection1);
trianglesPositive.Add(verticsPositive.Count);
trianglesPositive.Add(verticsPositive.Count + 1);
trianglesPositive.Add(verticsPositive.Count + 2);
verticsPositive.Add(point0);
verticsPositive.Add(pointIntersection1);
verticsPositive.Add(pointIntersection2);
}
else
{
trianglesNegative.Add(verticsNegative.Count);
trianglesNegative.Add(verticsNegative.Count + 1);
trianglesNegative.Add(verticsNegative.Count + 2);
verticsNegative.Add(point0);
verticsNegative.Add(point1);
verticsNegative.Add(pointIntersection1);
trianglesNegative.Add(verticsNegative.Count);
trianglesNegative.Add(verticsNegative.Count + 1);
trianglesNegative.Add(verticsNegative.Count + 2);
verticsNegative.Add(point0);
verticsNegative.Add(pointIntersection1);
verticsNegative.Add(pointIntersection2);
}
}
public static bool LinePlaneIntersection(out Vector3 intersection, Vector3 linePoint, Vector3 lineVec, Vector3 planeNormal, Vector3 planePoint)
{
float length;
float dotNumerator;
float dotDenominator;
Vector3 vector;
intersection = Vector3.zero;
dotNumerator = Vector3.Dot((planePoint - linePoint), planeNormal);
dotDenominator = Vector3.Dot(lineVec, planeNormal);
if (dotDenominator != 0.0f)
{
length = dotNumerator / dotDenominator;
vector = SetVectorLength(lineVec, length);
intersection = linePoint + vector;
return true;
}
else
return false;
}