XNA CustomVertices

Creating a Custom Vertex in XNA

Here is a declaration of a custom vertex that implements position, texture, normal, tangent and bitangent properties.

The declaration also has to implement the "IVertexType" interface, which details how the vertex declaration is returned to the effect.

Make the vertex Serializable into XML (or Binary) by using the [Serializable] Attribute:

using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;
using System;

    [Serializable]
    public struct VertexPosTexNormalTanBitan : IVertexType
    {

Now we declare the member elements of the vertex

        Vector3 pos;
        Vector2 tex;
        Vector3 normal, tan, bitan;

Create a static member to hold the VertexDeclaration definition with the VertexElements supported by the declaration

    public static readonly VertexDeclaration VertexDeclaration = new VertexDeclaration
    (
        new VertexElement(0, VertexElementFormat.Vector3, VertexElementUsage.Position, 0),
        new VertexElement(sizeof(float) * 3, VertexElementFormat.Vector2, VertexElementUsage.TextureCoordinate, 0),
        new VertexElement(sizeof(float) * 5, VertexElementFormat.Vector3, VertexElementUsage.Normal, 0),
        new VertexElement(sizeof(float) * 8, VertexElementFormat.Vector3, VertexElementUsage.Tangent, 0),
        new VertexElement(sizeof(float) * 11, VertexElementFormat.Vector3, VertexElementUsage.Binormal, 0)
    );

And a constructor that sets the member variables

    public VertexPosTexNormalTanBitan(Vector3 position, 
                                      Vector2 uv, 
                                      Vector3 normal, 
                                      Vector3 tan, 
                                      Vector3 bitan)
    {
        pos = position;
        tex = uv;
        this.normal = normal;
        this.tan = tan;
        this.bitan = bitan;
    }

As per the IVertexType Interface, you need to implement the VertexDeclaration property for the Custom Vertex type as follows:

    VertexDeclaration IVertexType.VertexDeclaration
    {
        get { return VertexDeclaration; }
    }

You can implement the != and == operators (not required).

    public static bool operator !=(VertexPosTexNormalTanBitan left, 
                                      VertexPosTexNormalTanBitan right)
    {
        return left.GetHashCode() != right.GetHashCode();
    }

    public static bool operator ==(VertexPosTexNormalTanBitan left, 
                                        VertexPosTexNormalTanBitan right)
    {
        return left.GetHashCode() == right.GetHashCode();
    }

As well as override the Equals() Method (not require).

    public override bool Equals(object obj)
    {
        return this == (VertexPosTexNormalTanBitan)obj;
    }

Lets declare some accessors for the member variables

    public Vector3 Position { get { return pos; } set { pos = value; } }
    public Vector3 Normal { get { return normal; } set { normal = value; } }
    public Vector2 Tex { get { return tex; } set { tex = value; } }
    public Vector3 Tan { get { return tan; } set { tan = value; } }
    public Vector3 Bitan { get { return bitan; } set { bitan = value; } }

A custom vertex can also implement the SizeInBytes() method to make it easier to create a VertexDeclaration based on the vertex type.

    public static int SizeInBytes { get { return sizeof(float) * 14; } }

As well as the GetHashCode() method (not required).

    public override int GetHashCode()
    {
        return pos.GetHashCode() | 
                 tex.GetHashCode() | 
                 normal.GetHashCode() | 
                 tan.GetHashCode() | 
                 bitan.GetHashCode();
    }

Finally we wrap it up by making a custom ToString() method to display the vertex in the debugger a little nicer (not required).

        public override string ToString()
        {
            return string.Format("{0},{1},{2}", pos.X, pos.Y, pos.Z);
        }
    }

Thats all there is to creating your own custom vertices for XNA :)