Sprite For GLK Renderig

//Based off of http://www.raywenderlich.com/9743/how-to-create-a-simple-2d-iphone-game-with-opengl-es-2-0-and-glkit-part-1

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using MonoTouch.Foundation;
using MonoTouch.GLKit;
using System.Drawing;
using OpenTK.Graphics.ES20;
using System.Runtime.InteropServices;

namespace XamarinSpriteAnimation
{
    public struct TexturedVertex
    {
        public PointF geomertryVertex;
        public PointF textureVertex;
    }

    public struct TexturedQuad
    {
        public TexturedVertex bl;
        public TexturedVertex br;
        public TexturedVertex tl;
        public TexturedVertex tr;
    }

    public class Sprite : NSObject
    {
        public string FileName { get; set; }
        GLKBaseEffect Effect { get; set; }
        GLKTextureInfo TextureInfo { get; set; }
        TexturedQuad Quad;

        public Sprite(string f, GLKBaseEffect e)
        {

            FileName = f;
            Effect = e;

            NSDictionary options = NSDictionary.FromObjectAndKey(NSNumber.FromBoolean(true), GLKTextureLoader.OriginBottomLeft);
            string path = NSBundle.MainBundle.PathForResource(FileName, null);
            NSError error;
            TextureInfo = GLKTextureLoader.FromFile(path, options, out error);

            // To Do: Set up textured Quad
            TexturedQuad someQuad = new TexturedQuad();
            someQuad.bl.geomertryVertex = new PointF(0, 0);
            someQuad.br.geomertryVertex = new PointF(TextureInfo.Width, 0);
            someQuad.tl.geomertryVertex = new PointF(0, TextureInfo.Height);
            someQuad.tr.geomertryVertex = new PointF(TextureInfo.Width, TextureInfo.Height);

            someQuad.bl.textureVertex = new PointF(0, 0);
            someQuad.br.textureVertex = new PointF(1, 0);
            someQuad.tl.textureVertex = new PointF(0, 1);
            someQuad.tr.textureVertex = new PointF(1, 1);

            Quad = someQuad;
        }

        public void Render()
        {
            Effect.Texture2d0.GLName = TextureInfo.Name;
            Effect.Texture2d0.Enabled = true;

            Effect.PrepareToDraw();

            GL.EnableVertexAttribArray((int)GLKVertexAttrib.Position);
            GL.EnableVertexAttribArray((int)GLKVertexAttrib.TexCoord0);

            IntPtr ptr = Marshal.AllocHGlobal(Marshal.SizeOf(Quad));
            Marshal.StructureToPtr(Quad, ptr, false);
            int offset = (int)ptr;

            GL.VertexAttribPointer((uint)GLKVertexAttrib.Position, 2, VertexAttribPointerType.Float, false, Marshal.SizeOf(typeof(TexturedVertex)), offset + (int)Marshal.OffsetOf(typeof(TexturedVertex), "geomertryVertex"));
            GL.VertexAttribPointer((uint)GLKVertexAttrib.Position, 2, VertexAttribPointerType.Float, false, Marshal.SizeOf(typeof(TexturedVertex)), offset + (int)Marshal.OffsetOf(typeof(TexturedVertex), "textureVertex"));

            GL.DrawArrays(BeginMode.TriangleStrip, 0, 4);

            Marshal.FreeHGlobal(ptr);
        }
    }
}