private void MakeIndexData()
{
IndexData16 = new IndexData16()
{
triangleCount = 2,
indices = new ushort[2 * 3]
};
/*
* indices = new ushort[triangleCount * 3];
*
* // Indices are encoded using the high water mark encoding from webgl-loader. Indices are decoded as follows:
* ushort highest = 0;
* for (int i = 0; i < indices.Length; i++)
* {
* ushort code = reader.ReadUInt16();
* indices[i] = (ushort)(highest - code);
*
* if (code == 0)
* highest++;
* }
*
*
*/
// triangles to draw anti clockwise
IndexData16.indices[0] = 0;
IndexData16.indices[1] = 3;
IndexData16.indices[2] = 1;
IndexData16.indices[3] = 0;
IndexData16.indices[4] = 2;
IndexData16.indices[5] = 3;
}
/// <summary>
/// This determines the order the triangles are made. Must be anti clockwise
/// </summary>
private void MakeTriangleIndices()
{
// winding should be anticlockwise
MeshIndexData16 = new IndexData16()
{
triangleCount = (uint)_TriangleCount,
indices = new ushort[_TriangleCount * 3]
};
try
{
int m = 0;
for (int y = 0; y < _GridSize - 1; y++) // bottom row to row just before top
{
// var r = (y * _GridSize) + y;
var r = y * _GridSize;
for (int x = 0; x < _GridSize - 1; x++)
{
/* MeshIndexData16.indices[m] = (ushort)(r);
* MeshIndexData16.indices[m+1] = (ushort)(r + _GridSize + 2);
* MeshIndexData16.indices[m+2] = (ushort)(r + _GridSize + 1);
* MeshIndexData16.indices[m+3] = (ushort)(r);
* MeshIndexData16.indices[m+4] = (ushort)(r+1);
* MeshIndexData16.indices[m+5] = (ushort)(r + _GridSize + 2);
*/
// triangle winding order is anti clockwise from SW, NE, NW, SW, SE, NE
MeshIndexData16.indices[m] = (ushort)(r);
MeshIndexData16.indices[m + 1] = (ushort)(r + _GridSize + 1);
MeshIndexData16.indices[m + 2] = (ushort)(r + _GridSize);
MeshIndexData16.indices[m + 3] = (ushort)(r);
MeshIndexData16.indices[m + 4] = (ushort)(r + 1);
MeshIndexData16.indices[m + 5] = (ushort)(r + _GridSize + 1);
m = m + 6;
r++;
}
}
}
catch (Exception exception)
{
Console.WriteLine($"Unexpected exception: {exception}");
}
// high water mark encoding
ushort highest = 0;
ushort code;
for (int i = 0; i < MeshIndexData16.indices.Length; i++)
{
code = (ushort)(highest - MeshIndexData16.indices[i]);
MeshIndexData16.indices[i] = code;
if (code == 0)
{
highest++;
}
}
}
public void EncodeIndices(IndexData16 idxData)
{
/*
*
* So you can also get a pretty big win by exploiting pre-transform vertex cache optimization.
* I call it “high water mark encoding.” Basically: for such a properly optimized index list,
* the next index you see is either (a) one you’ve seen before or (b) one higher than the current highest seen index.
* So, instead of encoding actual indices, you can instead encode them relative to this high water mark (the largest index yet to be seen, initialized to 0).
* You see “n” and that corresponds to an index of (high water mark – n). When you see 0, you also increment high watermark.
* The benefit here is that the encoded indices are very small, and then you can do some kind of varint coding,
* then your encoded indices are a bit more than a byte on average. If you plan on zipping later, then make sure the variants are byte-aligned and LSB-first.
*
* uint16_t highest = 0;
* uint16_t code;
*
* // Write main indices
* for (size_t i = 0, icount = mMesh.indices.size(); i < icount; i++) {
* code = highest - mMesh.indices[i];
* ostream.write(&code, sizeof(uint16_t));
* if (code == 0) highest++;
* }
*
* // Write all vertices on the edge of the tile (W, S, E, N)
* writeEdgeIndices<uint16_t>(ostream, mMesh, bounds.min.x, 0);
* writeEdgeIndices<uint16_t>(ostream, mMesh, bounds.min.y, 1);
* writeEdgeIndices<uint16_t>(ostream, mMesh, bounds.max.x, 0);
* writeEdgeIndices<uint16_t>(ostream, mMesh, bounds.max.y, 1);
* }
*
*
*/
ushort highest = 0;
ushort code;
for (int i = 0; i < idxData.indices.Length; i++)
{
code = (ushort)(highest - idxData.indices[i]);
idxData.indices[i] = code;
if (code == 0)
{
highest++;
}
}
/*
* triangleCount = reader.ReadUInt32();
* indices = new ushort[triangleCount * 3];
*
* // Indices are encoded using the high water mark encoding from webgl-loader. Indices are decoded as follows:
* ushort highest = 0;
* for (int i = 0; i<indices.Length; i++)
* {
* ushort code = reader.ReadUInt16();
* indices[i] = (ushort) (highest - code);
*
* if (code == 0)
* highest++;
* }
*/
}
