/// <summary>
/// Generate Tangent BiNormal from an existing vertex/index buffer.
/// </summary>
/// <param name="vertexDeclaration">The vertex declaration of the vertex buffer passed by parameters.</param>
/// <param name="vertexBufferData">The vertex buffer.</param>
/// <param name="vertexCount">The vertex count.</param>
/// <param name="vertexOffset">The vertex offset.</param>
/// <param name="vertexStride">The vertex stride. If 0, It takes the stride from the vertex declaration</param>
/// <param name="indexData">The index data.</param>
/// <param name="is32BitIndex">if set to <c>true</c> [is32 bit index].</param>
/// <param name="indexCountArg">The index count argument.</param>
/// <returns>A new vertex buffer with its new layout.</returns>
public static unsafe VertexTransformResult GenerateTangentBinormal(VertexDeclaration vertexDeclaration, IntPtr vertexBufferData, int vertexCount, int vertexOffset, int vertexStride, IntPtr indexData, bool is32BitIndex, int indexCountArg)
{
if (vertexDeclaration == null)
{
throw new ArgumentNullException("vertexDeclaration");
}
if (vertexBufferData == IntPtr.Zero)
{
throw new ArgumentNullException("vertexBufferData");
}
if (vertexCount <= 0)
{
throw new ArgumentOutOfRangeException("vertexCount", "vertexCount must be > 0");
}
if (vertexStride < 0)
{
throw new ArgumentOutOfRangeException("vertexStride", "vertexStride must be >= 0");
}
if (indexData != IntPtr.Zero && indexCountArg < 0)
{
throw new ArgumentOutOfRangeException("indexCountArg", "indexCountArg must be >= 0");
}
// Get the stride from the vertex declaration if necessary
if (vertexStride == 0)
{
vertexStride = vertexDeclaration.VertexStride;
}
var indexBufferBinding = indexData;
var oldVertexStride = vertexStride;
var bufferData = vertexBufferData;
// TODO: Usage index in key
var offsetMapping = vertexDeclaration
.EnumerateWithOffsets()
.ToDictionary(x => x.VertexElement.SemanticAsText, x => x.Offset);
var positionOffset = offsetMapping["POSITION"];
var uvOffset = offsetMapping[VertexElementUsage.TextureCoordinate];
var normalOffset = offsetMapping[VertexElementUsage.Normal];
// Add tangent to vertex declaration
var vertexElements = vertexDeclaration.VertexElements.ToList();
if (!offsetMapping.ContainsKey(VertexElementUsage.Tangent))
{
vertexElements.Add(VertexElement.Tangent <Vector4>());
}
var newVertexDeclaration = new VertexDeclaration(vertexElements.ToArray());
var newVertexStride = newVertexDeclaration.VertexStride;
// Update mapping
offsetMapping = newVertexDeclaration
.EnumerateWithOffsets()
.ToDictionary(x => x.VertexElement.SemanticAsText, x => x.Offset);
var tangentOffset = offsetMapping[VertexElementUsage.Tangent];
var newBufferData = new byte[vertexCount * newVertexStride];
var tangents = new Vector3[vertexCount];
var bitangents = new Vector3[vertexCount];
byte *indexBufferStart = (byte *)indexData;
byte *oldBuffer = (byte *)bufferData + vertexOffset;
fixed(byte *newBuffer = newBufferData)
{
var indexBuffer32 = indexBufferBinding != IntPtr.Zero && is32BitIndex ? (int *)indexBufferStart : null;
var indexBuffer16 = indexBufferBinding != IntPtr.Zero && !is32BitIndex ? (short *)indexBufferStart : null;
var indexCount = indexBufferBinding != IntPtr.Zero ? indexCountArg : vertexCount;
for (int i = 0; i < indexCount; i += 3)
{
// Get indices
int index1 = i + 0;
int index2 = i + 1;
int index3 = i + 2;
if (indexBuffer32 != null)
{
index1 = indexBuffer32[index1];
index2 = indexBuffer32[index2];
index3 = indexBuffer32[index3];
}
else if (indexBuffer16 != null)
{
index1 = indexBuffer16[index1];
index2 = indexBuffer16[index2];
index3 = indexBuffer16[index3];
}
int vertexOffset1 = index1 * oldVertexStride;
int vertexOffset2 = index2 * oldVertexStride;
int vertexOffset3 = index3 * oldVertexStride;
// Get positions
var position1 = (Vector3 *)&oldBuffer[vertexOffset1 + positionOffset];
var position2 = (Vector3 *)&oldBuffer[vertexOffset2 + positionOffset];
var position3 = (Vector3 *)&oldBuffer[vertexOffset3 + positionOffset];
// Get texture coordinates
var uv1 = (Vector2 *)&oldBuffer[vertexOffset1 + uvOffset];
var uv2 = (Vector2 *)&oldBuffer[vertexOffset2 + uvOffset];
var uv3 = (Vector2 *)&oldBuffer[vertexOffset3 + uvOffset];
// Calculate position and UV vectors from vertex 1 to vertex 2 and 3
var edge1 = *position2 - *position1;
var edge2 = *position3 - *position1;
var uvEdge1 = *uv2 - *uv1;
var uvEdge2 = *uv3 - *uv1;
var dR = uvEdge1.X * uvEdge2.Y - uvEdge2.X * uvEdge1.Y;
// Workaround to handle degenerated case
// TODO: We need to understand more how we can handle this more accurately
if (MathUtil.IsZero(dR))
{
dR = 1;
}
var r = 1.0f / dR;
var t = (uvEdge2.Y * edge1 - uvEdge1.Y * edge2) * r;
var b = (uvEdge1.X * edge2 - uvEdge2.X * edge1) * r;
// Contribute to every vertex
tangents[index1] += t;
tangents[index2] += t;
tangents[index3] += t;
bitangents[index1] += b;
bitangents[index2] += b;
bitangents[index3] += b;
}
var oldVertexOffset = 0;
var newVertexOffset = 0;
for (int i = 0; i < vertexCount; ++i)
{
Utilities.CopyMemory(new IntPtr(&newBuffer[newVertexOffset]), new IntPtr(&oldBuffer[oldVertexOffset]), oldVertexStride);
var normal = *(Vector3 *)&oldBuffer[oldVertexOffset + normalOffset];
var newTangentPtr = ((float *)(&newBuffer[newVertexOffset + tangentOffset]));
var tangent = tangents[i];
var bitangent = bitangents[i];
// Gram-Schmidt orthogonalize
var newTangentUnormalized = tangent - normal * Vector3.Dot(normal, tangent);
var length = newTangentUnormalized.Length();
// Workaround to handle degenerated case
// TODO: We need to understand more how we can handle this more accurately
if (MathUtil.IsZero(length))
{
tangent = Vector3.Cross(normal, Vector3.UnitX);
if (MathUtil.IsZero(tangent.Length()))
{
tangent = Vector3.Cross(normal, Vector3.UnitY);
}
tangent.Normalize();
*((Vector3 *)newTangentPtr) = tangent;
bitangent = Vector3.Cross(normal, tangent);
}
else
{
*((Vector3 *)newTangentPtr) = newTangentUnormalized / length;
}
// Calculate handedness
newTangentPtr[3] = Vector3.Dot(Vector3.Cross(normal, tangent), bitangent) < 0.0f ? -1.0f : 1.0f;
oldVertexOffset += oldVertexStride;
newVertexOffset += newVertexStride;
}
return(new VertexTransformResult(newVertexDeclaration, newBufferData));
}
}
/// <summary>
/// Generates multi texture coordinates for an existing vertex buffer. See remarks.
/// </summary>
/// <param name="vertexDeclaration">The vertex declaration.</param>
/// <param name="vertexBufferData">The vertex buffer data.</param>
/// <param name="vertexCount">The vertex count.</param>
/// <param name="vertexOffset">The vertex offset.</param>
/// <param name="vertexStride">The vertex stride.</param>
/// <param name="maxTexcoord">The maximum texcoord.</param>
/// <returns>A new vertex buffer with additional texture coordinates.</returns>
/// <exception cref="System.ArgumentNullException">
/// vertexDeclaration
/// or
/// vertexBufferData
/// </exception>
/// <exception cref="System.ArgumentOutOfRangeException">
/// vertexCount;vertexCount must be > 0
/// or
/// vertexStride;vertexStride must be >= 0
/// or
/// maxTexcoord;maxTexcoord must be > 0
/// </exception>
/// <exception cref="System.InvalidOperationException">The vertex buffer must contain at least the TEXCOORD</exception>
/// <remarks>
/// The original vertex buffer must contain at least a TEXCOORD[0-9] attribute in order for this method to work.
/// This method will copy the value of the first existing TEXCOORD found in the vertex buffer to the newly created TEXCOORDS.
/// </remarks>
public static unsafe VertexTransformResult GenerateMultiTextureCoordinates(VertexDeclaration vertexDeclaration, IntPtr vertexBufferData, int vertexCount, int vertexOffset, int vertexStride, int maxTexcoord = 9)
{
if (vertexDeclaration == null)
{
throw new ArgumentNullException("vertexDeclaration");
}
if (vertexBufferData == IntPtr.Zero)
{
throw new ArgumentNullException("vertexBufferData");
}
if (vertexCount <= 0)
{
throw new ArgumentOutOfRangeException("vertexCount", "vertexCount must be > 0");
}
if (vertexStride < 0)
{
throw new ArgumentOutOfRangeException("vertexStride", "vertexStride must be >= 0");
}
if (maxTexcoord < 0)
{
throw new ArgumentOutOfRangeException("maxTexcoord", "maxTexcoord must be > 0");
}
// Get the stride from the vertex declaration if necessary
if (vertexStride == 0)
{
vertexStride = vertexDeclaration.VertexStride;
}
// TODO: Usage index in key
var offsetMapping = vertexDeclaration
.EnumerateWithOffsets()
.ToDictionary(x => x.VertexElement.SemanticAsText, x => x.Offset);
var newVertexElements = new List <VertexElement>();
int vertexUVOffset = -1;
// Use R16G16_SNorm as it is supported from HW Level 9.1
// See https://msdn.microsoft.com/en-us/library/windows/desktop/ff471324%28v=vs.85%29.aspx
const PixelFormat DefaultUVFormat = PixelFormat.R16G16_SNorm;
var newUvSize = DefaultUVFormat.SizeInBytes();
for (int i = 0; i <= maxTexcoord; i++)
{
var vertexElement = VertexElement.TextureCoordinate(i, DefaultUVFormat);
var semantic = vertexElement.SemanticAsText;
if (offsetMapping.TryGetValue(semantic, out int offset))
{
if (vertexUVOffset < 0)
{
vertexUVOffset = offset;
}
}
else
{
newVertexElements.Add(vertexElement);
}
}
if (vertexUVOffset < 0)
{
throw new InvalidOperationException("The vertex buffer must contain at least the TEXCOORD");
}
var newVertexStride = vertexStride + newVertexElements.Count * newUvSize;
var newVertexBuffer = new byte[newVertexStride * vertexCount];
byte *oldBuffer = (byte *)vertexBufferData + vertexOffset;
fixed(byte *newBuffer = newVertexBuffer)
{
var oldVertexOffset = 0;
var newVertexOffset = 0;
for (int i = 0; i < vertexCount; ++i)
{
Utilities.CopyMemory(new IntPtr(&newBuffer[newVertexOffset]), new IntPtr(&oldBuffer[oldVertexOffset]), vertexStride);
var textureCoord = *(Vector2 *)&oldBuffer[oldVertexOffset + vertexUVOffset];
for (int j = 0; j < newVertexElements.Count; j++)
{
var target = ((Half2 *)(&newBuffer[newVertexOffset + vertexStride + j * newUvSize]));
* target = (Half2)textureCoord;
}
oldVertexOffset += vertexStride;
newVertexOffset += newVertexStride;
}
}
var allVertexElements = new List <VertexElement>(vertexDeclaration.VertexElements);
allVertexElements.AddRange(newVertexElements);
return(new VertexTransformResult(new VertexDeclaration(allVertexElements.ToArray()), newVertexBuffer));
}