/// <summary>
/// Converts input channels that are used for colors from Vector3/Vector4
/// to single float format, if necessary.
/// </summary>
/// <param name="inputChannels">Vertex Channels as read from COLLADA file</param>
private void ConvertColorChannels(List <VertexChannel> inputChannels)
{
foreach (VertexChannel channel in inputChannels)
{
var usage = channel.Description.VertexElementUsage;
var format = channel.Description.VertexElementFormat;
if (usage != VertexElementUsage.Color)
{
continue; // only relevant for colors
}
if (format == VertexElementFormat.Single)
{
continue; // nothing to do
}
// Create updated vertex element description where each element is a single
VertexElement newDesc = new VertexElement()
{
Offset = 0,
UsageIndex = channel.Description.UsageIndex,
VertexElementFormat = VertexElementFormat.Single,
VertexElementUsage = VertexElementUsage.Color
};
// Old stride is 3 or 4 (corresponding to Vector3 or Vector4)
int oldStride = channel.Source.Stride;
float[] oldData = channel.Source.Data;
// Create new source where each color is only represented by one single
VertexSource newSource = new VertexSource();
newSource.Stride = 1; // one float per color
newSource.Data = new float[oldData.Length / oldStride];
for (int i = 0; i < newSource.Data.Length; i++)
{
// project start index to old data set (with $oldStride components per color)
int j = i * oldStride;
// Construct color from three or four floats in range [0,1]
Color color = (oldStride == 3) ?
new Color(oldData[j + 0], oldData[j + 1], oldData[j + 2]) :
new Color(oldData[j + 0], oldData[j + 1], oldData[j + 2], oldData[j + 3]);
newSource.Data[i] = ConvertColorToSingle(color);
}
// Update description and source of channel
channel.Description = newDesc;
channel.Source = newSource;
}
}
/// <summary>
/// Creates a new Vertex Channel
/// </summary>
/// <param name="source">Used vertex source</param>
/// <param name="description">Vertex element description</param>
/// <param name="indices">Indices</param>
public VertexChannel(VertexSource source, VertexElement description)
{
Source = source;
Description = description;
}
/// <summary>
/// Creates a vertex container from a set of "raw" vertex channels as read from the COLLADA file.
/// Hence, it is assumed that each channel uses its own source (rather than every channel using
/// the same single source).
/// </summary>
/// <param name="inputChannels">Original Input Channels from COLLADA file</param>
public VertexContainer(List <VertexChannel> inputChannels)
{
// Check for basic requirements
if (inputChannels.Any(c => c.Description.VertexElementUsage == VertexElementUsage.Position) == false)
{
throw new ArgumentException("Geometry has not all needed information. At least Positions are necessary!");
}
// Convert Colors to single values, if necessary
ConvertColorChannels(inputChannels);
// Number of floats per vertex
_vertexSize = CalculateVertexSize(inputChannels);
// Expected number of indices
int numIndices = inputChannels.First().Indices.Length;
// vertex buffer with an expected number of 3/4 of the number of indices
List <float> vbuffer = new List <float>(numIndices * 3 / 4);
// Remember the position of distinct vertices to avoid duplicates
Dictionary <VertexKey, int> usedVertices = new Dictionary <VertexKey, int>(numIndices * 3 / 4);
// Indices referencing the new vertex buffer (vbuffer)
List <int> indexList = new List <int>(numIndices);
// Go through all indices to create vertices
for (int i = 0; i < numIndices; i++)
{
VertexKey key = new VertexKey(inputChannels, i);
int usedIndex = 0;
if (usedVertices.TryGetValue(key, out usedIndex))
{
// This vertex was already used, its index is "usedIndex"
indexList.Add(usedIndex);
}
else
{
// If the vertex is unknown, add it to the vertex container (channel-wise)
// and remember that is has been used and the corresponding index
int index = vbuffer.Count / _vertexSize;
// Add all elements of the current vertex to the vertex buffer
foreach (VertexChannel channel in inputChannels)
{
float[] elementData = new float[channel.Source.Stride];
channel.GetValue(i, ref elementData, 0);
// origin of texture coordinates in XNA is top left, while
// in COLLADA it is bottom left. Therefore they need to be
// converted here
if (channel.Description.VertexElementUsage == VertexElementUsage.TextureCoordinate)
{
elementData[1] = 1 - elementData[1];
}
vbuffer.AddRange(elementData);
}
// Remember that this vertex combination was used before
// and store the index where it can be found in the
// vertex container
usedVertices.Add(key, index);
// Add reference to the just created vertex to the index list / buffer
indexList.Add(index);
}
}
// Create adequate vertex channels
int offset = 0;
foreach (VertexChannel inputChannel in inputChannels)
{
VertexSource newSource = new VertexSource()
{
Offset = offset // the element-offset within the vertex buffer
};
VertexElement desc = new VertexElement(offset, inputChannel.Description.VertexElementFormat,
inputChannel.Description.VertexElementUsage, inputChannel.Description.UsageIndex);
VertexChannel newChannel = new VertexChannel(newSource, desc);
_vertexChannels.Add(newChannel);
offset += inputChannel.Source.Stride;
}
// Swap winding order
for (int i = 0; i < indexList.Count; i += 3)
{
int swap = indexList[i + 1];
indexList[i + 1] = indexList[i + 2];
indexList[i + 2] = swap;
}
_data = vbuffer.ToArray();
_indices = indexList.ToArray();
// Update Source Data reference off all vertex channels
foreach (VertexChannel channel in _vertexChannels)
{
// Every channel uses the same source now (global vertex buffer)
channel.Source.Data = _data;
// Every channel also uses the same indices
channel.Indices = _indices;
// The stride of one entry containing all elements for one vertex
channel.Source.Stride = _vertexSize;
}
}
