/// <summary>
/// collect triangles by group id. Returns array of triangle lists (stored as arrays).
/// This requires 2 passes over mesh, but each pass is linear
/// </summary>
public static int[][] FindTriangleSetsByGroup(DMesh3 mesh, int ignoreGID = int.MinValue)
{
if (!mesh.HasTriangleGroups)
{
return(new int[0][]);
}
// find # of groups and triangle count for each
SparseList <int> counts = CountAllGroups(mesh);
List <int> GroupIDs = new List <int>();
foreach (var idxval in counts.Values())
{
if (idxval.Key != ignoreGID && idxval.Value > 0)
{
GroupIDs.Add(idxval.Key);
}
}
GroupIDs.Sort(); // might as well sort ascending...
SparseList <int> groupMap = new SparseList <int>(mesh.MaxGroupID, GroupIDs.Count, -1);
// allocate sets
int[][] sets = new int[GroupIDs.Count][];
int[] counters = new int[GroupIDs.Count];
for (int i = 0; i < GroupIDs.Count; ++i)
{
int gid = GroupIDs[i];
sets[i] = new int[counts[gid]];
counters[i] = 0;
groupMap[gid] = i;
}
// accumulate triangles
int NT = mesh.MaxTriangleID;
for (int tid = 0; tid < NT; ++tid)
{
if (mesh.IsTriangle(tid))
{
int gid = mesh.GetTriangleGroup(tid);
int i = groupMap[gid];
if (i >= 0)
{
int k = counters[i]++;
sets[i][k] = tid;
}
}
}
return(sets);
}
/// <summary>
/// count number of tris in each group in mesh
/// returned pairs are [group_id, tri_count]
/// </summary>
public static SparseList <int> CountAllGroups(DMesh3 mesh)
{
SparseList <int> GroupCounts = new SparseList <int>(mesh.MaxGroupID, 0, 0);
if (mesh.HasTriangleGroups)
{
int NT = mesh.MaxTriangleID;
for (int tid = 0; tid < NT; ++tid)
{
if (mesh.IsTriangle(tid))
{
int gid = mesh.GetTriangleGroup(tid);
GroupCounts[gid] = GroupCounts[gid] + 1;
}
}
}
return(GroupCounts);
}