// Build the tree. Policy only matters for bottom-up strategies
public void Build(BuildStrategy eStrategy = BuildStrategy.TopDownMidpoint,
ClusterPolicy ePolicy = ClusterPolicy.Default)
{
if (eStrategy == BuildStrategy.BottomUpFromOneRings)
{
build_by_one_rings(ePolicy);
}
else if (eStrategy == BuildStrategy.TopDownMedian)
{
build_top_down(true);
}
else if (eStrategy == BuildStrategy.TopDownMidpoint)
{
build_top_down(false);
}
else if (eStrategy == BuildStrategy.Default)
{
build_top_down(false);
}
mesh_timestamp = mesh.Timestamp;
}
// strategy here is:
// 1) partition triangles by vertex one-rings into leaf boxes
// 1a) first pass where we skip one-rings that have < 3 free tris
// 1b) second pass where we handle any missed tris
// 2) sequentially combine N leaf boxes into (N/2 + N%2) layer 2 boxes
// 3) repeat until layer K has only 1 box, which is root of tree
void build_by_one_rings(ClusterPolicy ePolicy)
{
box_to_index = new DVector <int>();
box_centers = new DVector <Vector3f>();
box_extents = new DVector <Vector3f>();
int iBoxCur = 0;
index_list = new DVector <int>();
int iIndicesCur = 0;
// replace w/ BitArray ?
byte[] used_triangles = new byte[mesh.MaxTriangleID];
Array.Clear(used_triangles, 0, used_triangles.Length);
// temporary buffer
int nMaxEdgeCount = mesh.GetMaxVtxEdgeCount();
int[] temp_tris = new int[2 * nMaxEdgeCount];
// first pass: cluster by one-ring, but if # of free tris
// in a ring is small (< 3), push onto spill list to try again,
// because those tris might be picked up by a bigger cluster
DVector <int> spill = new DVector <int>();
foreach (int vid in mesh.VertexIndices())
{
int tCount = add_one_ring_box(vid, used_triangles, temp_tris,
ref iBoxCur, ref iIndicesCur, spill, 3);
if (tCount < 3)
{
spill.Add(vid);
}
}
// second pass: check any spill vertices. Most are probably gone
// now, but a few stray triangles might still exist
int N = spill.Length;
for (int si = 0; si < N; ++si)
{
int vid = spill[si];
add_one_ring_box(vid, used_triangles, temp_tris,
ref iBoxCur, ref iIndicesCur, null, 0);
}
// [RMS] test code to make sure each triangle is in exactly one list
//foreach ( int tid in mesh.TriangleIndices() ) {
// int n = used_triangles[tid];
// if (n != 1)
// Util.gBreakToDebugger();
//}
// keep track of where triangle lists end
triangles_end = iIndicesCur;
// this defines ClusterPolicy.Default
//ClusterFunctionType clusterF = cluster_boxes;
//ClusterFunctionType clusterF = cluster_boxes_matrix;
ClusterFunctionType clusterF = cluster_boxes_nearsearch;
if (ePolicy == ClusterPolicy.Fastest)
{
clusterF = cluster_boxes;
}
else if (ePolicy == ClusterPolicy.MinimalVolume)
{
clusterF = cluster_boxes_matrix;
}
else if (ePolicy == ClusterPolicy.FastVolumeMetric)
{
clusterF = cluster_boxes_nearsearch;
}
// ok, now repeatedly cluster current layer of N boxes into N/2 + N%2 boxes,
// until we hit a 1-box layer, which is root of the tree
int nPrevEnd = iBoxCur;
int nLayerSize = clusterF(0, iBoxCur, ref iBoxCur, ref iIndicesCur);
int iStart = nPrevEnd;
int iCount = iBoxCur - nPrevEnd;
while (nLayerSize > 1)
{
nPrevEnd = iBoxCur;
nLayerSize = clusterF(iStart, iCount, ref iBoxCur, ref iIndicesCur);
iStart = nPrevEnd;
iCount = iBoxCur - nPrevEnd;
}
root_index = iBoxCur - 1;
}