how to get the modulus of Bezier

I have code for Bezier Curver,but I don't understand how to get the modulus

the code :

Code (csharp):

1.  
2.     public Vector3 GetPointAtTime( float t )
3.  
4.     {
5.  
6.         this.CheckConstant();
7.  
8.         float t2 = t * t;
9.  
10.         float t3 = t * t * t;
11.  
12.         float x = this.Ax * t3 + this.Bx * t2 + this.Cx * t + p0.x;
13.  
14.         float y = this.Ay * t3 + this.By * t2 + this.Cy * t + p0.y;
15.  
16.         float z = this.Az * t3 + this.Bz * t2 + this.Cz * t + p0.z;
17.  
18.         return new Vector3( x, y, z );
19.  
20.  
21.  
22.     }
23.  
24.  
25.  
26.     private void SetConstant()
27.  
28.     {
29.  
30. [B][COLOR="#FF8C00"][COLOR="#008000"]        this.Cx = 3f * ( ( this.p0.x + this.p1.x ) - this.p0.x );
31.  
32.         this.Bx = 3f * ( ( this.p3.x + this.p2.x ) - ( this.p0.x + this.p1.x ) ) - this.Cx;
33.  
34.         this.Ax = this.p3.x - this.p0.x - this.Cx - this.Bx;
35.  
36.  
37.  
38.         this.Cy = 3f * ( ( this.p0.y + this.p1.y ) - this.p0.y );
39.  
40.         this.By = 3f * ( ( this.p3.y + this.p2.y ) - ( this.p0.y + this.p1.y ) ) - this.Cy;
41.  
42.         this.Ay = this.p3.y - this.p0.y - this.Cy - this.By;
43.  
44.  
45.  
46.         this.Cz = 3f * ( ( this.p0.z + this.p1.z ) - this.p0.z );
47.  
48.         this.Bz = 3f * ( ( this.p3.z + this.p2.z ) - ( this.p0.z + this.p1.z ) ) - this.Cz;
49.  
50.         this.Az = this.p3.z - this.p0.z - this.Cz - this.Bz;[/COLOR][/COLOR][/B]
51.  
52.  
53.  
54.     }
55.  

Thanks!

 

I want to get a 2 order Bessel,how to make it