/// <summary>
/// Get Instancing VertexDeclaration
/// </summary>
/// <param name="gd"></param>
/// <returns></returns>
public VertexDeclaration InstancingVDec(GraphicsDevice gd)
{
// When using hardware instancing, the instance transform matrix is
// specified using a second vertex stream that provides 4x4 matrices
// in texture coordinate channels 1 to 4. We must modify our vertex
// declaration to include these channels.
VertexElement[] extraElements = new VertexElement[4];
short offset = 0;
byte usageIndex = 1;
short stream = 1;
for (int i = 0; i < extraElements.Length; i++)
{
extraElements[i] = new VertexElement(stream, offset,
VertexElementFormat.Vector4,
VertexElementMethod.Default,
VertexElementUsage.TextureCoordinate,
usageIndex);
offset += SLConstant.SizeOfVector4;
usageIndex++;
}
// Append the new elements to the original format.
int length = VertexPositionColor.VertexElements.Length + extraElements.Length;
VertexElement[] elements = new VertexElement[length];
VertexPositionColor.VertexElements.CopyTo(elements, 0);
extraElements.CopyTo(elements, VertexPositionColor.VertexElements.Length);
// Create a new vertex declaration.
return(new VertexDeclaration(gd, elements));
}