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DX11 GPUList<T>: A C# list class with a DX11 Buffer backend

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Hey everyone,

So earlier today, I was playing with some compute shader stuff, and I found myself getting very frustrated dealing with buffers, copying the data back and forth, ect...
I thought, it would be really nice if there was some kind of pretty C# interface to a list of data stored on the GPU...

Well, I never found one, so I wrote my own! I would like to share it in hopes that it will cure at least one more headache.

Its essentially an implementation of IList<T> which is backed using a SlimDX Buffer.
Any operation you do directly affects this underlying buffer.
Therefor, its very easy to make a list of data to give / receive to / from your shaders.

Its not perfect, but it gets the job done. Its pretty, easy to use, and (somewhat) tested.

Source code for the List and a small test program are below.
Please let me know if you have comments, suggestions, fixes, or find any bugs.

~Chris

[ps I tried attaching the .cs files directly but it doesn't like them?]



using System;
using System.Collections.Generic;
using System.Linq;

using SlimDX;
using SlimDX.Direct3D11;
using SlimDX.DXGI;
using SlimDX.D3DCompiler;

using Device = SlimDX.Direct3D11.Device;
using Buffer = SlimDX.Direct3D11.Buffer;

namespace GPUTools
{
class Program
{
/// <summary>
/// Simple structure representing some kind of particle
/// </summary>
struct Particle
{
public Vector3 Position;
public Vector3 Velocity;

public override string ToString()
{
return "Position: " + Position.ToString() + ", Velocity: " + Velocity.ToString();
}
}

static void Main(string[] args)
{
// Source code for the simple integration compute shader
const string integrateSource = @"

struct Particle
{
float3 position;
float3 velocity;
};

RWStructuredBuffer<Particle> particles;

[numthreads(1, 1, 1)]
void Integrate(uint3 threadID : SV_DispatchThreadID)
{
particles[threadID.x].position += particles[threadID.x].velocity;
}
";

// Make device
Device device = new Device(DriverType.Hardware, DeviceCreationFlags.None, FeatureLevel.Level_10_0);

// Compile compute shader
ShaderBytecode integrateBytecode = ShaderBytecode.Compile(integrateSource, "Integrate", "cs_4_0", ShaderFlags.None, EffectFlags.None);
ComputeShader integrate = new ComputeShader(device, integrateBytecode);

// Create GPUList of particles using the immediate context
GPUList<Particle> particles = new GPUList<Particle>(device.ImmediateContext);
// Add some particles
for (int i = 0; i < 10; i++)
particles.Add(new Particle() { Position = new Vector3(i, 0, 0), Velocity = new Vector3(0, i, -i) });

// Print the particles
Console.WriteLine("Before Integration:");
foreach (Particle p in particles)
Console.WriteLine(p.ToString());

// Run the compute shader
device.ImmediateContext.ComputeShader.Set(integrate);
device.ImmediateContext.ComputeShader.SetUnorderedAccessView(particles.UnorderedAccess, 0);
device.ImmediateContext.Dispatch(particles.Count, 1, 1);

// Print the particles again
Console.WriteLine("\n\nAfter Integration:");
foreach (Particle p in particles)
Console.WriteLine(p.ToString());

Console.Read();
}
}
}





/* Who: Chris Giles
* What: A GPU-based implementation of List<T>
* When: 5/16/2011 @ ~4 AM
* Where: My house
* Why: I was tired of dealing with low level graphics resources
* This is almost completely interchangable with built in C# List<T>
* Only, the backend is a DirectX11 Buffer
* You can use the underlying buffer in any kind of shader
* But with a pretty C# interface for messing with its data
*/

using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.InteropServices;

using SlimDX;
using SlimDX.Direct3D11;

using Device = SlimDX.Direct3D11.Device;
using Buffer = SlimDX.Direct3D11.Buffer;

namespace GPUTools
{
public class GPUList<T> : IList<T>, IDisposable where T : struct
{
#region GPUList Members

private DeviceContext context;
private Buffer buffer;
private ShaderResourceView shaderResourceView;
private UnorderedAccessView unorderedAccessView;

private int count;
private int capacity;

/// <summary>
/// Makes a new list given initial data
/// </summary>
/// <param name="context">Device context on which to perform all operations</param>
public GPUList(DeviceContext context)
{
this.context = context;
}

/// <summary>
/// Makes a new empty list with an initial capacity
/// </summary>
/// <param name="context">Device context on which to perform all operations</param>
/// <param name="initialCapacity">The initial capacity</param>
public GPUList(DeviceContext context, int initialCapacity)
{
this.context = context;
this.setCapacity(initialCapacity);
}

/// <summary>
/// Makes a new list given initial data
/// </summary>
/// <param name="context">Device context on which to perform all operations</param>
/// <param name="data">The initial data</param>
public GPUList(DeviceContext context, IEnumerable<T> data)
{
this.context = context;
this.AddRange(data);
}

/// <summary>
/// Gets the DeviceContext on which to perform all operations
/// </summary>
public DeviceContext Context { get { return context; } }

/// <summary>
/// Gets the underlying Buffer stored on the GPU
/// </summary>
public Buffer GPUBuffer { get { return buffer; } }

/// <summary>
/// Gets a ShaderResourceView for use in a shader
/// </summary>
public ShaderResourceView ShaderResource { get { return shaderResourceView; } }

/// <summary>
/// Gets a UnorderedAccessView for use in a shader
/// </summary>
public UnorderedAccessView UnorderedAccess { get { return unorderedAccessView; } }

/// <summary>
/// Gets or Sets the internal GPU buffer capacity in number of elements
/// </summary>
public int Capacity { get { return capacity; } set { setCapacity(value); } }

/// <summary>
/// Adds a range of items to the end of the list
/// </summary>
/// <param name="range"></param>
public void AddRange(IEnumerable<T> range)
{
if (range == null)
throw new ArgumentNullException();

int dataSize = Marshal.SizeOf(typeof(T));

if (range is GPUList<T> && range != this)
{
GPUList<T> list = range as GPUList<T>;

if (list.Count == 0)
return;
if (Count + list.Count > Capacity)
setCapacity(2 * Count + list.Count);

count += list.Count;

list.CopyRangeTo(0, list.Count, this, Count - list.Count);
}
else
{
T[] data = null;
if (range is T[])
data = (T[])range;
else if (range is List<T>)
data = (range as List<T>).ToArray();
else
{
List<T> dataList = new List<T>(range);
data = dataList.ToArray();
}

if (data.Length == 0)
return;
if (Count + data.Length > Capacity)
setCapacity(2 * Count + data.Length);

count += data.Length;

SetRange(Count - data.Length, data, 0, data.Length);
}
}

/// <summary>
/// Inserts a range of items into the list
/// </summary>
/// <param name="index">Position in the list to insert items</param>
/// <param name="range">The range of items to insert</param>
public void InsertRange(int index, IEnumerable<T> range)
{
if (range == null)
throw new ArgumentNullException();
if (index < 0 || index > Count)
throw new IndexOutOfRangeException();

if (index == Count)
{
AddRange(range);
}
else
{
GPUList<T> newList = null;

if (range is GPUList<T>)
{
GPUList<T> list = range as GPUList<T>;

if (list.Count == 0)
return;

newList = new GPUList<T>(Context, list.Count + Count);
newList.count = list.Count + Count;
this.CopyRangeTo(0, index, newList, 0);
list.CopyTo(newList, index);
this.CopyRangeTo(index, Count - index, newList, index + list.Count);
}
else
{
T[] data = null;
if (range is T[])
data = (T[])range;
else if (range is List<T>)
data = (range as List<T>).ToArray();
else
{
List<T> dataList = new List<T>(range);
data = dataList.ToArray();
}

if (data.Length == 0)
return;

newList = new GPUList<T>(Context, data.Length + Count);
newList.count = data.Length + Count;
this.CopyRangeTo(0, index, newList, 0);
newList.SetRange(index, data, 0, data.Length);
this.CopyRangeTo(index, Count - index, newList, index + data.Length);
}

setCapacity(0);
count = newList.count;
capacity = newList.capacity;
buffer = newList.buffer;
shaderResourceView = newList.shaderResourceView;
unorderedAccessView = newList.unorderedAccessView;
}
}

/// <summary>
/// Removes a range of items from the list
/// </summary>
/// <param name="index">Index to start removing</param>
/// <param name="count">Number of items to remove</param>
public void RemoveRange(int index, int count)
{
if (count == 0)
return;

if (count < 0)
throw new IndexOutOfRangeException();
if (index < 0 || index >= Count)
throw new IndexOutOfRangeException();
if (index + count < 0 || index + count > Count)
throw new IndexOutOfRangeException();

if (index + count == Count)
{
this.count -= count;
return;
}

GPUList<T> newList = new GPUList<T>(Context, Capacity);
newList.count = this.count - count;
this.CopyRangeTo(0, index, newList, 0);
this.CopyRangeTo(index + count, this.count - (index + count), newList, index);

setCapacity(0);
this.count = newList.count;
this.capacity = newList.capacity;
this.buffer = newList.buffer;
this.shaderResourceView = newList.shaderResourceView;
this.unorderedAccessView = newList.unorderedAccessView;
}

/// <summary>
/// Sets a range of data in the list based on an array
/// </summary>
/// <param name="index">Index in the GPUList to start setting data</param>
/// <param name="array">The array of data to use</param>
/// <param name="arrayIndex">The start index in the array</param>
/// <param name="count">The number of elements to set</param>
public void SetRange(int index, T[] array, int arrayIndex, int count)
{
if (count == 0)
return;

if (count < 0)
throw new IndexOutOfRangeException();
if (index < 0 || index >= Count)
throw new IndexOutOfRangeException();
if (index + count < 0 || index + count > Count)
throw new IndexOutOfRangeException();

if (array == null)
throw new ArgumentNullException();
if (arrayIndex < 0 || arrayIndex >= array.Length)
throw new IndexOutOfRangeException();
if (arrayIndex + array.Length < 0 || arrayIndex + count > array.Length)
throw new IndexOutOfRangeException();

int dataSize = Marshal.SizeOf(typeof(T));
DataStream stream = new DataStream(array, true, false);
stream.Seek(arrayIndex, System.IO.SeekOrigin.Begin);
context.UpdateSubresource(new DataBox(0, 0, stream), buffer, 0,
new ResourceRegion(dataSize * index, 0, 0, dataSize * (index + count), 1, 1));
}

/// <summary>
/// Copies a range of data to an array
/// </summary>
/// <param name="index">Index from which to start copying</param>
/// <param name="count">Number of elements to copy</param>
/// <param name="array">Destination array to copy to</param>
/// <param name="arrayIndex">Destination array index to copy to</param>
public void CopyRangeTo(int index, int count, T[] array, int arrayIndex)
{
if (count == 0)
return;

if (count < 0)
throw new IndexOutOfRangeException();
if (index < 0 || index >= Count)
throw new IndexOutOfRangeException();
if (index + count < 0 || index + count > Count)
throw new IndexOutOfRangeException();

if (array == null)
throw new ArgumentNullException();
if (arrayIndex < 0 || arrayIndex >= array.Length)
throw new IndexOutOfRangeException();
if (arrayIndex + array.Length < 0 || arrayIndex + count > array.Length)
throw new IndexOutOfRangeException();

int dataSize = Marshal.SizeOf(typeof(T));
Buffer stagingBuffer = new Buffer(context.Device, dataSize * count, ResourceUsage.Staging,
BindFlags.None, CpuAccessFlags.Read, ResourceOptionFlags.None, 0);

context.CopySubresourceRegion(buffer, 0,
new ResourceRegion(dataSize * index, 0, 0, dataSize * (index + count), 1, 1),
stagingBuffer, 0, 0, 0, 0);

DataBox box = context.MapSubresource(stagingBuffer, 0, dataSize * count,
MapMode.Read, SlimDX.Direct3D11.MapFlags.None);
box.Data.ReadRange<T>(array, arrayIndex, count);
context.UnmapSubresource(stagingBuffer, 0);

stagingBuffer.Dispose();
}

/// <summary>
/// Copies a range of data to another GPUList
/// </summary>
/// <param name="index">Index from which to start copying</param>
/// <param name="count">Number of elements to copy</param>
/// <param name="list">Destination list to copy to</param>
/// <param name="listIndex">Destination list index to copy to</param>
public void CopyRangeTo(int index, int count, GPUList<T> list, int listIndex)
{
if (count == 0)
return;

if (list == this)
throw new Exception("Cannot copy range into self...yet");

if (count < 0)
throw new IndexOutOfRangeException();
if (index < 0 || index >= Count)
throw new IndexOutOfRangeException();
if (index + count < 0 || index + count > Count)
throw new IndexOutOfRangeException();

if (list == null)
throw new ArgumentNullException();
if (listIndex < 0 || listIndex >= list.Count)
throw new IndexOutOfRangeException();
if (listIndex + list.Count < 0 || listIndex + count > list.Count)
throw new IndexOutOfRangeException();

int dataSize = Marshal.SizeOf(typeof(T));
context.CopySubresourceRegion(buffer, 0,
new ResourceRegion(dataSize * index, 0, 0, dataSize * (index + count), 1, 1),
list.buffer, 0, dataSize * listIndex, 0, 0);
}

/// <summary>
/// Copys the list to another GPUList
/// </summary>
/// <param name="array">The list to copy data to</param>
/// <param name="arrayIndex">The starting index in the array</param>
public void CopyTo(GPUList<T> list, int listIndex)
{
CopyRangeTo(0, count, list, listIndex);
}

/// <summary>
/// Trims excess capacity on the internal GPU buffer to match the count
/// </summary>
public void TrimExcess()
{
setCapacity(Count);
}

/// <summary>
/// Returns a copy of the list into an array
/// </summary>
/// <returns></returns>
public T[] ToArray()
{
T[] data = new T[Count];
CopyTo(data, 0);
return data;
}

/// <summary>
/// Sets the internal capacity of the list
/// </summary>
/// <param name="newCapacity"></param>
private void setCapacity(int newCapacity)
{
if (newCapacity < 0)
throw new ArgumentOutOfRangeException();

if (newCapacity == capacity)
return;

if (newCapacity == 0)
{
if (unorderedAccessView != null)
unorderedAccessView.Dispose();
if (shaderResourceView != null)
shaderResourceView.Dispose();
if (buffer != null)
buffer.Dispose();

unorderedAccessView = null;
shaderResourceView = null;
buffer = null;

capacity = count = 0;
return;
}

int dataSize = Marshal.SizeOf(typeof(T));
Buffer newBuffer = new Buffer(context.Device, dataSize * newCapacity, ResourceUsage.Default,
BindFlags.ShaderResource | BindFlags.UnorderedAccess,
CpuAccessFlags.None, ResourceOptionFlags.StructuredBuffer, dataSize);

int sizeToCopy = Math.Min(newCapacity, Count);
if (sizeToCopy > 0)
context.CopySubresourceRegion(buffer, 0, new ResourceRegion(0, 0, 0, dataSize * sizeToCopy, 1, 1), newBuffer, 0, 0, 0, 0);

count = sizeToCopy;
capacity = newCapacity;

if (unorderedAccessView != null)
unorderedAccessView.Dispose();
if (shaderResourceView != null)
shaderResourceView.Dispose();
if (buffer != null)
buffer.Dispose();

buffer = newBuffer;
unorderedAccessView = new UnorderedAccessView(context.Device, buffer);
shaderResourceView = new ShaderResourceView(context.Device, buffer);
}

#endregion

#region IDisposable Members

/// <summary>
/// Disposes the list by destroying all GPU resources used
/// </summary>
public void Dispose()
{
setCapacity(0);
}

#endregion

#region IList<T> Members

/// <summary>
/// Adds one item to the end of the list
/// </summary>
/// <param name="item">The item to add</param>
public void Add(T item)
{
T[] array = new T[] { item };
AddRange(array);
}

/// <summary>
/// Gets the index in the list of the first item found
/// </summary>
/// <param name="item">The item whose index is searched for</param>
/// <returns>Index of the item found, or -1 if not found</returns>
public int IndexOf(T item)
{
T[] data = new T[count];
CopyTo(data, 0);

for (int i = 0; i < data.Length; i++)
if (data.Equals(item))
return i;
return -1;
}

/// <summary>
/// Inserts an item at a specific index
/// </summary>
/// <param name="index">The index in the list to insert the item</param>
/// <param name="item">The item to insert</param>
public void Insert(int index, T item)
{
T[] array = new T[] { item };
InsertRange(index, array);
}

/// <summary>
/// Removes an item at a specific index
/// </summary>
/// <param name="index"></param>
public void RemoveAt(int index)
{
RemoveRange(index, 1);
}

/// <summary>
/// Gets or Sets an element at some index in the list
/// </summary>
/// <param name="index">Index in the list to get or set</param>
/// <returns></returns>
public T this[int index]
{
get
{
if (index < 0 || index >= count)
throw new IndexOutOfRangeException();

T[] array = new T[1];
CopyRangeTo(index, 1, array, 0);
return array[0];
}
set
{
if (index < 0 || index >= count)
throw new IndexOutOfRangeException();

T[] array = new T[] { value };
SetRange(index, array, 0, 1);
}
}

#endregion

#region ICollection<T> Members

/// <summary>
/// Clears the list of all elements
/// </summary>
public void Clear()
{
count = 0;
}

/// <summary>
/// Returns true if the item is contained in the list, or false if not
/// </summary>
/// <param name="item">The item to check containment for</param>
/// <returns></returns>
public bool Contains(T item)
{
foreach (T i in this)
if (i.Equals(item))
return true;
return false;
}

/// <summary>
/// Copys the list to an array
/// </summary>
/// <param name="array">The array to copy data to</param>
/// <param name="arrayIndex">The starting index in the array</param>
public void CopyTo(T[] array, int arrayIndex)
{
CopyRangeTo(0, count, array, arrayIndex);
}

/// <summary>
/// Gets the number of items in the list
/// </summary>
public int Count { get { return count; } }

/// <summary>
/// Returns whether or not the list is read only
/// </summary>
public bool IsReadOnly { get { return false; } }

/// <summary>
/// Removes an item from the list. Only the first item found is removed
/// </summary>
/// <param name="item">The item to remove</param>
/// <returns>True if the item is removed, false otherwise</returns>
public bool Remove(T item)
{
int index = IndexOf(item);
if (index >= 0)
RemoveAt(index);
return index >= 0;
}

#endregion

#region IEnumerable<T> Members

/// <summary>
/// Gets the enumerator for this list. Any changes made while enumerating will not be reflected
/// </summary>
/// <returns></returns>
public IEnumerator<T> GetEnumerator()
{
T[] array = new T[count];
CopyTo(array, 0);
return array.AsEnumerable<T>().GetEnumerator();
}

#endregion

#region IEnumerable Members

/// <summary>
/// Gets the enumerator for this list. Any changes made while enumerating will not be reflected
/// </summary>
/// <returns></returns>
System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
{
return GetEnumerator();
}

#endregion
}
}

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              [7]    0.023804742479357766    
              [8]    0.0033238872995488885    
       
      I would have liked it to be more "rounded" at the top, or a better spread instead of wasting [0], [1], [2] with values bellow 0.1.
      Based on my experiments, the key to this is to provide a different sigma, but if I do, my kernel values no longer adds up to 1, which results to a darker blur.
      I've found this post 
      ... which helped me a bit, but I am really confused with this the part where he divide sigma by 3.
      Can someone please explain how sigma works? How is it related to my kernel size, how can I balance my weights with different sigmas, ect...
       
      Thanks :-)
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