/// <summary>
/// Creates a <see cref="VertexBuffer{T}"/> with specified length, optional index buffer and usage hint.
/// </summary>
/// <param name="graphicsDevice">The <see cref="GraphicsDevice"/> this <see cref="VertexBuffer{T}"/> will use.</param>
/// <param name="storageLength">The length for the <see cref="VertexBuffer{T}"/>'s element storage measured in vertices.</param>
/// <param name="indexStorageLength">The length for the <see cref="VertexBuffer{T}"/>'s index storage measured in index elements, or 0 for no index storage.</param>
/// <param name="indexElementType">The type of index element to use.</param>
/// <param name="usageHint">Used by the graphics driver to optimize performance.</param>
public VertexBuffer(GraphicsDevice graphicsDevice, uint storageLength, uint indexStorageLength, DrawElementsType indexElementType, BufferUsageARB usageHint)
{
ValidateStorageLength(storageLength);
ElementSize = (uint)Marshal.SizeOf <T>();
uint bufferStorageLengthBytes;
uint elementSubsetLengthBytes = storageLength * ElementSize;
bool hasIndexBuffer = indexStorageLength > 0;
uint indexSubsetStartBytes;
if (hasIndexBuffer)
{
uint indexElementSize = IndexBufferSubset.GetSizeInBytesOfElementType(indexElementType);
indexSubsetStartBytes = (elementSubsetLengthBytes + indexElementSize - 1) / indexElementSize * indexElementSize;
bufferStorageLengthBytes = indexSubsetStartBytes + indexElementSize * indexStorageLength;
}
else
{
indexSubsetStartBytes = 0;
bufferStorageLengthBytes = elementSubsetLengthBytes;
}
Buffer = new BufferObject(graphicsDevice, bufferStorageLengthBytes, usageHint);
DataSubset = new VertexDataBufferSubset <T>(Buffer, 0, storageLength);
IndexBufferSubset indexSubset = hasIndexBuffer ? new IndexBufferSubset(Buffer, indexSubsetStartBytes, indexStorageLength, indexElementType) : null;
VertexArray = VertexArray.CreateSingleBuffer <T>(graphicsDevice, DataSubset, indexSubset);
}
/// <summary>
/// Creates a <see cref="VertexArray"/>
/// </summary>
/// <param name="graphicsDevice">The <see cref="GraphicsDevice"/> this resource will use.</param>
/// <param name="attribSources">
/// The <see cref="VertexAttribSource"/> array that will be stored by this <see cref="VertexArray"/>.
/// The library user must NOT have a reference to this array!
/// </param>
/// <param name="indexBuffer">An index buffer to attach to the vertex array, null if none is desired.</param>
/// <param name="compensateStructPadding">Whether to compensate for struct padding. Default is true.</param>
/// <param name="paddingPackValue">The struct packing value for compensating for padding. Default is 4.</param>
internal VertexArray(GraphicsDevice graphicsDevice, VertexAttribSource[] attribSources, IndexBufferSubset indexBuffer = null, bool compensateStructPadding = true, uint paddingPackValue = 4)
: base(graphicsDevice)
{
EnsureAttribsValid(attribSources);
this.attribSources = attribSources;
Handle = GL.GenVertexArray();
IndexBuffer = indexBuffer;
UpdateVertexAttributes(compensateStructPadding, paddingPackValue); //this also binds the vertex array
}
/// <summary>
/// Creates a <see cref="VertexArray"/> in which all the vertex attributes come interleaved from the same data buffer.
/// </summary>
/// <param name="graphicsDevice">The <see cref="GraphicsDevice"/> this resource will use.</param>
/// <param name="bufferSubset">The data buffer that stores all the vertex attributes.</param>
/// <param name="attribDescriptions">The descriptions of the vertex attributes.</param>
/// <param name="indexBuffer">An index buffer to attach to the vertex array, null if none is desired.</param>
/// <param name="compensateStructPadding">Whether to compensate for struct padding. Default is true.</param>
/// <param name="paddingPackValue">The struct packing value for compensating for padding. Default is 4.</param>
public VertexArray(GraphicsDevice graphicsDevice, DataBufferSubset bufferSubset, ReadOnlySpan <VertexAttribDescription> attribDescriptions, IndexBufferSubset indexBuffer = null, bool compensateStructPadding = true, uint paddingPackValue = 4)
: this(graphicsDevice, MakeAttribList(bufferSubset, attribDescriptions), indexBuffer, compensateStructPadding, paddingPackValue)
{
}
/// <summary>
/// Creates a <see cref="VertexArray"/> with the specified attribute sources.
/// </summary>
/// <param name="graphicsDevice">The <see cref="GraphicsDevice"/> this resource will use.</param>
/// <param name="attribSources">The sources from which the data of the vertex attributes will come from.</param>
/// <param name="indexBuffer">An index buffer to attach to the vertex array, null if none is desired.</param>
/// <param name="compensateStructPadding">Whether to compensate for struct padding. Default is true.</param>
/// <param name="paddingPackValue">The struct packing value for compensating for padding. Default is 4.</param>
public VertexArray(GraphicsDevice graphicsDevice, ReadOnlySpan <VertexAttribSource> attribSources, IndexBufferSubset indexBuffer = null, bool compensateStructPadding = true, uint paddingPackValue = 4)
: this(graphicsDevice, attribSources.ToArray(), indexBuffer, compensateStructPadding, paddingPackValue)
{
}
/// <summary>
/// Creates a <see cref="VertexArray"/> for the specified vertex type, where all of the vertex attributes come interleaved from the same buffer subset.
/// </summary>
/// <typeparam name="T">The type of vertex to use.</typeparam>
/// <param name="graphicsDevice">The <see cref="GraphicsDevice"/> this resource will use.</param>
/// <param name="dataBuffer">The buffer from which all attributes come from.</param>
/// <param name="indexBuffer">An index buffer to attach to the vertex array, null if none is desired.</param>
/// <param name="compensateStructPadding">Whether to compensate for struct padding. Default is true.</param>
/// <param name="paddingPackValue">The struct packing value for compensating for padding. Default is 4.</param>
public static VertexArray CreateSingleBuffer <T>(GraphicsDevice graphicsDevice, DataBufferSubset dataBuffer, IndexBufferSubset indexBuffer = null, bool compensateStructPadding = true, uint paddingPackValue = 4) where T : unmanaged, IVertex
{
T t = default;
int attribCount = t.AttribDescriptionCount;
Span <VertexAttribDescription> attribDescriptions = attribCount > 32 ?
new VertexAttribDescription[attribCount] : stackalloc VertexAttribDescription[attribCount];
t.WriteAttribDescriptions(attribDescriptions);
return(new VertexArray(graphicsDevice, dataBuffer, attribDescriptions, indexBuffer, compensateStructPadding, paddingPackValue));
}
