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XNA Newbie question:

I'm trying to get the GPU to perform some calculations for me. I'm trying to figure out how to send some data to the GPU, get the GPU to process it, then get the result back. I've modified some code as below:

HLSL:

texture2D Input0;
sampler2D Input0Sampler = sampler_state
{
    Texture = <Input0>;
    MinFilter = Point;
    MagFilter = Point;
    MipFilter = Point;
    AddressU = Clamp;
    AddressV = Clamp;
};

texture2D Input1;
sampler2D Input1Sampler = sampler_state
{
    Texture = <Input1>;
    MinFilter = Point;
    MagFilter = Point;
    MipFilter = Point;
    AddressU = Clamp;
    AddressV = Clamp;
};

texture2D Input2;
sampler2D Input2Sampler = sampler_state
{
    Texture = <Input2>;
    MinFilter = Point;
    MagFilter = Point;
    MipFilter = Point;
    AddressU = Clamp;
    AddressV = Clamp;
};

texture2D Input3;
sampler2D Input3Sampler = sampler_state
{
    Texture = <Input3>;
    MinFilter = Point;
    MagFilter = Point;
    MipFilter = Point;
    AddressU = Clamp;
    AddressV = Clamp;
};


struct VertexShaderInput
{
    float4 Position : POSITION0;
    float2 TextureCoordinate : TEXCOORD0;
};

struct VertexShaderOutput
{
    float4 Position : POSITION0;
    float2 TextureCoordinate : TEXCOORD0;
};

struct PixelShaderOutput
{
    // TODO: Optionally add/remove output indices to match GPUProcessor.numOutputs
    float4 Index0 : COLOR0;
};

VertexShaderOutput VertexShaderFunction(VertexShaderInput vsInput)
{
    VertexShaderOutput output;

    output.Position = vsInput.Position;
    output.TextureCoordinate = vsInput.TextureCoordinate;

    return output;
}

PixelShaderOutput PixelShaderFunction(VertexShaderOutput psInput)
{
    PixelShaderOutput output;

    // TODO: Optionally add/remove samples to match GPUProcessor.numInputs
    //float4 input0 = tex2D(Input0Sampler, psInput.TextureCoordinate);
    //float4 input1 = tex2D(Input0Sampler, psInput.TextureCoordinate);
    //float4 input2 = tex2D(Input0Sampler, psInput.TextureCoordinate);
    //float4 input3 = tex2D(Input0Sampler, psInput.TextureCoordinate);

    // your calculations go here

    // TODO: Optionally add/remove outputs to match GPUProcessor.numOutputs
    output.Index0 = float4(100,200,13,24);//input0;

    return output;
}

technique Verlet
{
    pass Go
    {
        VertexShader = compile vs_1_1 VertexShaderFunction();
        PixelShader = compile ps_2_0 PixelShaderFunction();
    }
}

C#

using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Audio;
using Microsoft.Xna.Framework.Content;
using Microsoft.Xna.Framework.GamerServices;
using Microsoft.Xna.Framework.Graphics;
using Microsoft.Xna.Framework.Input;
using Microsoft.Xna.Framework.Media;

namespace HLSLTest
{
    /// <summary>
    /// This is the main type for your game
    /// </summary>
    public class Game1 : Microsoft.Xna.Framework.Game
    {
        GraphicsDeviceManager graphics;
        SpriteBatch spriteBatch;

        Texture2D tex;
        RenderTarget2D renOutput;

        Vector4[] cpuStore = new Vector4[1920 * 1080];
        Vector4[] gpuStore = new Vector4[1920 * 1080];

        Effect effect;

        public Game1()
        {
            graphics = new GraphicsDeviceManager(this);
            Content.RootDirectory = "Content";
        }

        /// <summary>
        /// Allows the game to perform any initialization it needs to before starting to run.
        /// This is where it can query for any required services and load any non-graphic
        /// related content.  Calling base.Initialize will enumerate through any components
        /// and initialize them as well.
        /// </summary>
        protected override void Initialize()
        {
            // TODO: Add your initialization logic here

            cpuStore = new Vector4[1920 * 1080];
            for (int i = 0; i < cpuStore.Length; i++)
            {
                cpuStore[i] = new Vector4(i);
                //gpuStore[i] = new Vector4(i);
            }


            base.Initialize();
        }

        /// <summary>
        /// LoadContent will be called once per game and is the place to load
        /// all of your content.
        /// </summary>
        protected override void LoadContent()
        {
            // Create a new SpriteBatch, which can be used to draw textures.
            spriteBatch = new SpriteBatch(GraphicsDevice);

            tex = new Texture2D(GraphicsDevice, 1920, 1080, false, SurfaceFormat.Vector4);
            renOutput = new RenderTarget2D(GraphicsDevice, 1920, 1080, false, SurfaceFormat.Vector4, DepthFormat.Depth24Stencil8);

            tex.SetData<Vector4>(cpuStore);


            effect = Content.Load<Effect>("Shader");

            base.LoadContent();

            // TODO: use this.Content to load your game content here
        }

        /// <summary>
        /// UnloadContent will be called once per game and is the place to unload
        /// all content.
        /// </summary>
        protected override void UnloadContent()
        {
            // TODO: Unload any non ContentManager content here
        }

        /// <summary>
        /// Allows the game to run logic such as updating the world,
        /// checking for collisions, gathering input, and playing audio.
        /// </summary>
        /// <param name="gameTime">Provides a snapshot of timing values.</param>
        protected override void Update(GameTime gameTime)
        {
            // Allows the game to exit
            if (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed)
                this.Exit();

            // TODO: Add your update logic here

            base.Update(gameTime);
        }

        /// <summary>
        /// This is called when the game should draw itself.
        /// </summary>
        /// <param name="gameTime">Provides a snapshot of timing values.</param>
        protected override void Draw(GameTime gameTime)
        {
            //GraphicsDevice.Clear(Color.CornflowerBlue);


            GraphicsDevice.SetRenderTarget(renOutput);
            //GraphicsDevice.Clear(Color.Black);
            effect.Techniques[0].Passes[0].Apply();
            //effect.Parameters["oldPositionTexture"].SetValue(Output);            
            effect.CurrentTechnique.Passes[0].Apply();

            GraphicsDevice.SetRenderTarget(null);
            renOutput.GetData<Vector4>(gpuStore);
            //tex.GetData<Vector4>(gpuStore);

            base.Draw(gameTime);
        }
    }
}

The trouble is, when I put a breakpoint in the program and check the results stored in gpuStore, it contains a big list of vectors all the same value {X:0.2666667 Y:0.1333333 Z:0.5333334 W:1}. I was expecting it to return the value specified in my shader "float4(100,200,13,24)"

EDIT:

I've made some modifications thanks to Nathan's Advice. Here's what I have now:

HLSL

texture2D Input0;
sampler2D Input0Sampler = sampler_state
{
    Texture = <Input0>;
    MinFilter = Point;
    MagFilter = Point;
    MipFilter = Point;
    AddressU = Clamp;
    AddressV = Clamp;
};

texture2D Input1;
sampler2D Input1Sampler = sampler_state
{
    Texture = <Input1>;
    MinFilter = Point;
    MagFilter = Point;
    MipFilter = Point;
    AddressU = Clamp;
    AddressV = Clamp;
};

texture2D Input2;
sampler2D Input2Sampler = sampler_state
{
    Texture = <Input2>;
    MinFilter = Point;
    MagFilter = Point;
    MipFilter = Point;
    AddressU = Clamp;
    AddressV = Clamp;
};

texture2D Input3;
sampler2D Input3Sampler = sampler_state
{
    Texture = <Input3>;
    MinFilter = Point;
    MagFilter = Point;
    MipFilter = Point;
    AddressU = Clamp;
    AddressV = Clamp;
};


struct VertexShaderInput
{
    float4 Position : POSITION0;
    float2 TextureCoordinate : TEXCOORD0;
};

struct VertexShaderOutput
{
    float4 Position : POSITION0;
    float2 TextureCoordinate : TEXCOORD0;
};

struct PixelShaderOutput
{
    // TODO: Optionally add/remove output indices to match GPUProcessor.numOutputs
    float4 Index0 : COLOR0;
};

// input texture dimensions
static const float w = 1920;
static const float h = 1080;

static const float2 pixel = float2(1.0 / w, 1.0 / h);
static const float2 halfPixel = float2(pixel.x / 2, pixel.y / 2);


VertexShaderOutput VertexShaderFunction(VertexShaderInput vsInput)
{
    //VertexShaderOutput output;

    //output.Position = vsInput.Position;
    //output.TextureCoordinate = vsInput.TextureCoordinate;

    VertexShaderOutput output;
    vsInput.Position.x =  vsInput.Position.x - 2*halfPixel.x;
    vsInput.Position.y =  vsInput.Position.y + 2*halfPixel.y;
    output.Position = vsInput.Position;
    output.TextureCoordinate = vsInput.TextureCoordinate ;
    return output;


    //return output;
}

PixelShaderOutput PixelShaderFunction(VertexShaderOutput psInput)
{
    PixelShaderOutput output;
    // TODO: Optionally add/remove samples to match GPUProcessor.numInputs
    //float4 input0 = tex2D(Input0Sampler, psInput.TextureCoordinate);
    //float4 input1 = tex2D(Input0Sampler, psInput.TextureCoordinate);
    //float4 input2 = tex2D(Input0Sampler, psInput.TextureCoordinate);
    //float4 input3 = tex2D(Input0Sampler, psInput.TextureCoordinate);

    // your calculations go here

    // TODO: Optionally add/remove outputs to match GPUProcessor.numOutputs
    output.Index0 = float4(100,200,13,24);//input0;

    return output;
}

technique Verlet
{
    pass Go
    {
        VertexShader = compile vs_2_0 VertexShaderFunction();
        PixelShader = compile ps_2_0 PixelShaderFunction();
    }
}

C#

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Audio;
using Microsoft.Xna.Framework.Content;
using Microsoft.Xna.Framework.GamerServices;
using Microsoft.Xna.Framework.Graphics;
using Microsoft.Xna.Framework.Input;
using Microsoft.Xna.Framework.Media;

namespace HLSLTest
{
    internal sealed class QuadRender
    {
        private VertexPositionTexture[] verts;
        private GraphicsDevice myDevice;
        private short[] ib = null;

        ///
        /// Loads the quad.
        ///
        ///
        public QuadRender(GraphicsDevice device)
        {
            myDevice = device;         
            verts = new VertexPositionTexture[]
            {
                new VertexPositionTexture
                (
                    new Vector3(0,0,0),
                    new Vector2(1,1)
                ),
                new VertexPositionTexture
                (
                    new Vector3(0,0,0),
                    new Vector2(0,1)
                ),
                new VertexPositionTexture
                (
                    new Vector3(0,0,0),
                    new Vector2(0,0)
                ),
                new VertexPositionTexture
                (
                    new Vector3(0,0,0),
                    new Vector2(1,0)
                )
            };

            ib = new short[] { 0, 1, 2, 2, 3, 0 };
        }             

        ///
        /// Draws the fullscreen quad.
        ///
        ///
        public void RenderFullScreenQuad(Effect effect)
        {
            effect.CurrentTechnique.Passes[0].Apply();
            RenderQuad(Vector2.One * -1, Vector2.One);
        }

        public void RenderQuad(Vector2 v1, Vector2 v2)
        {          

            verts[0].Position.X = v2.X;
            verts[0].Position.Y = v1.Y;

            verts[1].Position.X = v1.X;
            verts[1].Position.Y = v1.Y;

            verts[2].Position.X = v1.X;
            verts[2].Position.Y = v2.Y;

            verts[3].Position.X = v2.X;
            verts[3].Position.Y = v2.Y;

            myDevice.DrawUserIndexedPrimitives(PrimitiveType.TriangleList, verts, 0, 4, ib, 0, 2);
        }
    }
}

the main program

using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Audio;
using Microsoft.Xna.Framework.Content;
using Microsoft.Xna.Framework.GamerServices;
using Microsoft.Xna.Framework.Graphics;
using Microsoft.Xna.Framework.Input;
using Microsoft.Xna.Framework.Media;

namespace HLSLTest
{
    /// <summary>
    /// This is the main type for your game
    /// </summary>
    public class Game1 : Microsoft.Xna.Framework.Game
    {
        GraphicsDeviceManager graphics;
        SpriteBatch spriteBatch;

        Texture2D tex;
        RenderTarget2D renOutput;

        Vector4[] cpuStore = new Vector4[1920 * 1080];
        Vector4[] gpuStore = new Vector4[1920 * 1080];

        Effect effect;
        QuadRender quad;
        public Game1()
        {
            graphics = new GraphicsDeviceManager(this);
            Content.RootDirectory = "Content";
        }

        /// <summary>
        /// Allows the game to perform any initialization it needs to before starting to run.
        /// This is where it can query for any required services and load any non-graphic
        /// related content.  Calling base.Initialize will enumerate through any components
        /// and initialize them as well.
        /// </summary>
        protected override void Initialize()
        {
            // TODO: Add your initialization logic here

            cpuStore = new Vector4[1920 * 1080];
            for (int i = 0; i < cpuStore.Length; i++)
            {
                cpuStore[i] = new Vector4(100*i);
                //gpuStore[i] = new Vector4(i);
            }


            base.Initialize();
        }

        /// <summary>
        /// LoadContent will be called once per game and is the place to load
        /// all of your content.
        /// </summary>
        protected override void LoadContent()
        {
            // Create a new SpriteBatch, which can be used to draw textures.
            spriteBatch = new SpriteBatch(GraphicsDevice);
            quad = new QuadRender(GraphicsDevice);

            tex = new Texture2D(GraphicsDevice, 1920, 1080, false, SurfaceFormat.Vector4);
            renOutput = new RenderTarget2D(GraphicsDevice, 1920, 1080, false, SurfaceFormat.Vector4, DepthFormat.Depth24);

            tex.SetData<Vector4>(cpuStore);


            effect = Content.Load<Effect>("Shader");

            base.LoadContent();

            // TODO: use this.Content to load your game content here
        }

        /// <summary>
        /// UnloadContent will be called once per game and is the place to unload
        /// all content.
        /// </summary>
        protected override void UnloadContent()
        {
            // TODO: Unload any non ContentManager content here
        }

        /// <summary>
        /// Allows the game to run logic such as updating the world,
        /// checking for collisions, gathering input, and playing audio.
        /// </summary>
        /// <param name="gameTime">Provides a snapshot of timing values.</param>
        protected override void Update(GameTime gameTime)
        {
            // Allows the game to exit
            if (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed)
                this.Exit();

            // TODO: Add your update logic here

            base.Update(gameTime);
        }

        /// <summary>
        /// This is called when the game should draw itself.
        /// </summary>
        /// <param name="gameTime">Provides a snapshot of timing values.</param>
        protected override void Draw(GameTime gameTime)
        {
            //GraphicsDevice.Clear(Color.CornflowerBlue);


            GraphicsDevice.SetRenderTarget(renOutput);
            //GraphicsDevice.Clear(Color.Black);
            effect.Parameters["Input0"].SetValue(cpuStore);
            quad.RenderFullScreenQuad(effect);
            for (int i = 0; i < effect.Techniques.Count; i++)
            {
                for (int j = 0; j < effect.Techniques[i].Passes.Count; j++)
                {
                    effect.Techniques[i].Passes[j].Apply();
                }
            }
            //effect.Techniques[0].Passes[0].Apply();
            //effect.Parameters["oldPositionTexture"].SetValue(Output);            
            //effect.CurrentTechnique.Passes[0].Apply();

            GraphicsDevice.SetRenderTarget(null);
            renOutput.GetData<Vector4>(gpuStore);
            //tex.GetData<Vector4>(gpuStore);

            base.Draw(gameTime);
        }
    }
}

Now I'm getting a runtime error

InvalidCastException was unhandled

Specified cast is not valid.

This is due to the line effect.Parameters["Input0"].SetValue(cpuStore);

EDIT

I can fix this if I can create my own Texture2D from a byte array.

For example if I use Emgu to load an image:

Image<Bgr, Byte> video = cap.QueryFrame();
Texture2D t = new Texture2D(GraphicsDevice, video.Width, video.Height, false, SurfaceFormat.Color);
t.SetData<byte>(video.Bytes);

But I get

ArgumentException was unhandled

The size of the data passed in is too large or too small for this resource.

share|improve this question
    
It doesn't look like you're drawing any geometry into the render target. You're applying the effect, but that doesn't in itself actually draw anything - it just sets the shader to be used for any following draws. Presumably you want to do a full-screen pass. Here is an article about doing that in XNA. –  Nathan Reed Jul 23 '13 at 4:08
    
I see from some of your code that you are interested in Verlet integration/updates. To do that, you might find it easiest to use the link Compute Shader –  axon Jul 23 '13 at 5:20
    
Actually the code example that I lifted this code from used the 'verlet' name. I'm actually interested in Perona Malik diffusion, which is what I finally want to write on the GPU. In any case, I am interested in the compute shader. –  sav Jul 23 '13 at 5:26
    
I'm currently studying this altdevblogaday.com/2011/10/02/… article to fix this problem. –  sav Jul 23 '13 at 7:08
    
In case you didn't know already, XNA doesn't support compute shaders. It uses D3D9, and compute shaders need at least D3D10, and preferably D3D11. SlimDX or SharpDX would be a better choice if you want to stick to C#. –  Adam Jul 23 '13 at 20:22
add comment

1 Answer

up vote 1 down vote accepted

OK

The final version

C#

using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Audio;
using Microsoft.Xna.Framework.Content;
using Microsoft.Xna.Framework.GamerServices;
using Microsoft.Xna.Framework.Graphics;
using Microsoft.Xna.Framework.Input;
using Microsoft.Xna.Framework.Media;
using Emgu.Util;
using Emgu.CV;
using Emgu.CV.Structure;

namespace HLSLTest
{
    public delegate void Disp();

    /// <summary>
    /// This is the main type for your game
    /// </summary>
    public class Game1 : Microsoft.Xna.Framework.Game
    {
        Capture cap = new Capture("output.avi");
        GraphicsDeviceManager graphics;
        SpriteBatch spriteBatch;

        RenderTarget2D renOutput;

        Vector4[] gpuStore = new Vector4[1920 * 1080];

        Effect effect;
        QuadRender quad;
        public Game1()
        {
            graphics = new GraphicsDeviceManager(this);
            Content.RootDirectory = "Content";
        }

        /// <summary>
        /// Allows the game to perform any initialization it needs to before starting to run.
        /// This is where it can query for any required services and load any non-graphic
        /// related content.  Calling base.Initialize will enumerate through any components
        /// and initialize them as well.
        /// </summary>
        protected override void Initialize()
        {
            // TODO: Add your initialization logic here

            base.Initialize();
        }

        /// <summary>
        /// LoadContent will be called once per game and is the place to load
        /// all of your content.
        /// </summary>
        protected override void LoadContent()
        {
            // Create a new SpriteBatch, which can be used to draw textures.
            spriteBatch = new SpriteBatch(GraphicsDevice);
            quad = new QuadRender(GraphicsDevice);

            renOutput = new RenderTarget2D(GraphicsDevice, 1920, 1080, false, SurfaceFormat.Vector4, DepthFormat.Depth24);

            effect = Content.Load<Effect>("Shader");

            base.LoadContent();

            // TODO: use this.Content to load your game content here
        }

        /// <summary>
        /// UnloadContent will be called once per game and is the place to unload
        /// all content.
        /// </summary>
        protected override void UnloadContent()
        {
            // TODO: Unload any non ContentManager content here
        }

        /// <summary>
        /// Allows the game to run logic such as updating the world,
        /// checking for collisions, gathering input, and playing audio.
        /// </summary>
        /// <param name="gameTime">Provides a snapshot of timing values.</param>
        protected override void Update(GameTime gameTime)
        {
            // Allows the game to exit
            if (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed)
                this.Exit();

            // TODO: Add your update logic here

            base.Update(gameTime);
        }

        /// <summary>
        /// This is called when the game should draw itself.
        /// </summary>
        /// <param name="gameTime">Provides a snapshot of timing values.</param>
        protected override void Draw(GameTime gameTime)
        {
            Image<Bgr, Byte> video = cap.QueryFrame();
            using (Image<Bgra, float> vid2 = video.Convert<Bgra, float>())
            {

                Texture2D t = new Texture2D(GraphicsDevice, video.Width, video.Height, false, SurfaceFormat.Vector4);
                t.SetData<byte>(vid2.Bytes);

                GraphicsDevice.SetRenderTarget(renOutput);
                effect.Parameters["Input0"].SetValue(t);
                quad.RenderFullScreenQuad(effect);
                for (int i = 0; i < effect.Techniques.Count; i++)
                {
                    for (int j = 0; j < effect.Techniques[i].Passes.Count; j++)
                    {
                        effect.Techniques[i].Passes[j].Apply();
                    }
                }

                GraphicsDevice.SetRenderTarget(null);
                renOutput.GetData<Vector4>(gpuStore);
            }

            base.Draw(gameTime);
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Audio;
using Microsoft.Xna.Framework.Content;
using Microsoft.Xna.Framework.GamerServices;
using Microsoft.Xna.Framework.Graphics;
using Microsoft.Xna.Framework.Input;
using Microsoft.Xna.Framework.Media;

namespace HLSLTest
{
    internal sealed class QuadRender
    {
        private VertexPositionTexture[] verts;
        private GraphicsDevice myDevice;
        private short[] ib = null;

        ///
        /// Loads the quad.
        ///
        ///
        public QuadRender(GraphicsDevice device)
        {
            myDevice = device;         
            verts = new VertexPositionTexture[]
            {
                new VertexPositionTexture
                (
                    new Vector3(0,0,0),
                    new Vector2(1,1)
                ),
                new VertexPositionTexture
                (
                    new Vector3(0,0,0),
                    new Vector2(0,1)
                ),
                new VertexPositionTexture
                (
                    new Vector3(0,0,0),
                    new Vector2(0,0)
                ),
                new VertexPositionTexture
                (
                    new Vector3(0,0,0),
                    new Vector2(1,0)
                )
            };

            ib = new short[] { 0, 1, 2, 2, 3, 0 };
        }             

        ///
        /// Draws the fullscreen quad.
        ///
        ///
        public void RenderFullScreenQuad(Effect effect)
        {
            effect.CurrentTechnique.Passes[0].Apply();
            RenderQuad(Vector2.One * -1, Vector2.One);
        }

        public void RenderQuad(Vector2 v1, Vector2 v2)
        {          

            verts[0].Position.X = v2.X;
            verts[0].Position.Y = v1.Y;

            verts[1].Position.X = v1.X;
            verts[1].Position.Y = v1.Y;

            verts[2].Position.X = v1.X;
            verts[2].Position.Y = v2.Y;

            verts[3].Position.X = v2.X;
            verts[3].Position.Y = v2.Y;

            myDevice.DrawUserIndexedPrimitives(PrimitiveType.TriangleList, verts, 0, 4, ib, 0, 2);
        }
    }
}

HLSL

texture2D Input0;
sampler2D Input0Sampler = sampler_state
{
    Texture = <Input0>;
    MinFilter = Point;
    MagFilter = Point;
    MipFilter = Point;
    AddressU = Clamp;
    AddressV = Clamp;
};

texture2D Input1;
sampler2D Input1Sampler = sampler_state
{
    Texture = <Input1>;
    MinFilter = Point;
    MagFilter = Point;
    MipFilter = Point;
    AddressU = Clamp;
    AddressV = Clamp;
};

texture2D Input2;
sampler2D Input2Sampler = sampler_state
{
    Texture = <Input2>;
    MinFilter = Point;
    MagFilter = Point;
    MipFilter = Point;
    AddressU = Clamp;
    AddressV = Clamp;
};

texture2D Input3;
sampler2D Input3Sampler = sampler_state
{
    Texture = <Input3>;
    MinFilter = Point;
    MagFilter = Point;
    MipFilter = Point;
    AddressU = Clamp;
    AddressV = Clamp;
};


struct VertexShaderInput
{
    float4 Position : POSITION0;
    float2 TextureCoordinate : TEXCOORD0;
};

struct VertexShaderOutput
{
    float4 Position : POSITION0;
    float2 TextureCoordinate : TEXCOORD0;
};

struct PixelShaderOutput
{
    // TODO: Optionally add/remove output indices to match GPUProcessor.numOutputs
    float4 Index0 : COLOR0;
};

// input texture dimensions
static const float w = 1920;
static const float h = 1080;

static const float2 pixel = float2(1.0 / w, 1.0 / h);
static const float2 halfPixel = float2(pixel.x / 2, pixel.y / 2);


VertexShaderOutput VertexShaderFunction(VertexShaderInput vsInput)
{
    //VertexShaderOutput output;

    //output.Position = vsInput.Position;
    //output.TextureCoordinate = vsInput.TextureCoordinate;

    VertexShaderOutput output;
    vsInput.Position.x =  vsInput.Position.x - 2*halfPixel.x;
    vsInput.Position.y =  vsInput.Position.y + 2*halfPixel.y;
    output.Position = vsInput.Position;
    output.TextureCoordinate = vsInput.TextureCoordinate ;
    return output;


    //return output;
}

PixelShaderOutput PixelShaderFunction(VertexShaderOutput psInput)
{
    PixelShaderOutput output;
    // TODO: Optionally add/remove samples to match GPUProcessor.numInputs
    float4 input0 = tex2D(Input0Sampler, psInput.TextureCoordinate);
    //float4 input1 = tex2D(Input0Sampler, psInput.TextureCoordinate);
    //float4 input2 = tex2D(Input0Sampler, psInput.TextureCoordinate);
    //float4 input3 = tex2D(Input0Sampler, psInput.TextureCoordinate);

    // your calculations go here

    // TODO: Optionally add/remove outputs to match GPUProcessor.numOutputs
    output.Index0 = input0;//float4(100,200,13,24);//input0;

    return output;
}

technique Verlet
{
    pass Go
    {
        VertexShader = compile vs_2_0 VertexShaderFunction();
        PixelShader = compile ps_2_0 PixelShaderFunction();
    }
}
share|improve this answer
    
Is this working? Else you should update your question –  Sidar Jul 24 '13 at 19:41
    
Yea, this is working. I'll mark this question as answered in a few more hours when Stack exchange lets me. –  sav Jul 24 '13 at 23:18
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