public TriangleStripper(ModelBase.FaceListDef faceList)
{
if (faceList.m_Type != ModelBase.PolyListType.Triangles)
{
bool tris = true;
for (int i = 0; i < faceList.m_Faces.Count; i++)
{
tris = (faceList.m_Faces[i].m_NumVertices == 3);
if (!tris)
{
throw new ArgumentException("The provided FaceListDef must be triangulated.");
}
}
faceList.m_Type = ModelBase.PolyListType.Triangles;
}
m_Vertices = new List <VertexLinked>();
m_Triangles = new List <TriangleLinked>();
m_TrianglesToProcess = new List <TriangleLinked>();
for (int i = 0; i < faceList.m_Faces.Count; i++)
{
if (IsDegenerateFace(faceList.m_Faces[i]))
{
faceList.m_Faces.RemoveAt(i);
}
}
for (int i = 0; i < faceList.m_Faces.Count; i++)
{
m_Triangles.Add(new TriangleLinked(faceList.m_Faces[i]));
}
for (int i = 0; i < m_Triangles.Count; i++)
{
ModelBase.FaceDef triangle = m_Triangles[i].m_Triangle;
for (int j = 0; j < triangle.m_NumVertices; j++)
{
VertexLinked vertex = new VertexLinked(triangle.m_Vertices[j]);
int index = m_Vertices.IndexOf(vertex);
if (index == -1)
{
m_Vertices.Add(vertex);
index = m_Vertices.Count - 1;
}
m_Vertices[index].m_LinkedTriangles.Add(i);
}
}
}
public List <ModelBase.FaceListDef> Stripify(bool keepVertexOrderDuringStripping = false)
{
for (int i = 0; i < m_Triangles.Count; i++)
{
ModelBase.FaceDef triangle = m_Triangles[i].m_Triangle;
List <int> vertexALinked = GetVertex(triangle.m_Vertices[0]).m_LinkedTriangles;
List <int> vertexBLinked = GetVertex(triangle.m_Vertices[1]).m_LinkedTriangles;
List <int> vertexCLinked = GetVertex(triangle.m_Vertices[2]).m_LinkedTriangles;
// Shares edge AB if both triangles reference vertices A and B
var edgeAB = vertexALinked.Intersect(vertexBLinked).Except(new int[] { i });
var edgeBC = vertexBLinked.Intersect(vertexCLinked).Except(new int[] { i });
var edgeCA = vertexCLinked.Intersect(vertexALinked).Except(new int[] { i });
if (edgeAB.Count() > 0)
{
m_Triangles[i].m_LinkedTriangles[(int)TriangleEdge.Edge_AB].AddRange(edgeAB);
}
if (edgeBC.Count() > 0)
{
m_Triangles[i].m_LinkedTriangles[(int)TriangleEdge.Edge_BC].AddRange(edgeBC);
}
if (edgeCA.Count() > 0)
{
m_Triangles[i].m_LinkedTriangles[(int)TriangleEdge.Edge_CA].AddRange(edgeCA);
}
}
m_TrianglesToProcess.AddRange(m_Triangles);
// Sort by number of neighbours
if (!keepVertexOrderDuringStripping)
{
m_TrianglesToProcess.Sort((a, b) => GetNumLinked(a).CompareTo(GetNumLinked(b)));
}
List <ModelBase.FaceListDef> tStrips = new List <ModelBase.FaceListDef>();
// For storing triangles that have no neighbours or don't end up in a strip
ModelBase.FaceListDef separateTriangles = new ModelBase.FaceListDef(ModelBase.PolyListType.Triangles);
TriangleLinked currentTriangle = null;
while (m_TrianglesToProcess.Count > 0)
{
while (true)
{
if (m_TrianglesToProcess.Count <= 0)
{
currentTriangle = null;
break;
}
currentTriangle = m_TrianglesToProcess[0];
m_TrianglesToProcess.RemoveAt(0);
if (currentTriangle.m_Marked)
{
continue;
}
else
{
break;
}
}
if (currentTriangle == null)
{
break;
}
List <TriangleLinked>[] linked = GetLinked(currentTriangle);
int numLinked = GetNumLinked(currentTriangle);
currentTriangle.m_Marked = true;
if (numLinked == 0)
{
separateTriangles.m_Faces.Add(currentTriangle.m_Triangle);
continue;
}
// For each face build a strip off each of its edges and keep the longest one, discarding the
// rest. Not part of SGI.
Tuple <ModelBase.FaceListDef, List <int> > tStripAB =
GetStripAndIndicesForStartingEvenEdge(currentTriangle, TriangleEdge.Edge_AB);
Tuple <ModelBase.FaceListDef, List <int> > tStripBC =
GetStripAndIndicesForStartingEvenEdge(currentTriangle, TriangleEdge.Edge_BC);
Tuple <ModelBase.FaceListDef, List <int> > tStripCA =
GetStripAndIndicesForStartingEvenEdge(currentTriangle, TriangleEdge.Edge_CA);
List <Tuple <ModelBase.FaceListDef, List <int> > > candidates = new List <Tuple <ModelBase.FaceListDef, List <int> > >()
{
tStripAB, tStripBC, tStripCA
};
List <int> stripLengths = new List <int>();
foreach (Tuple <ModelBase.FaceListDef, List <int> > strip in candidates)
{
stripLengths.Add(strip.Item1.m_Faces.Count);
}
int longestStripIndex = stripLengths.IndexOf(stripLengths.Max());
Tuple <ModelBase.FaceListDef, List <int> > longestStrip = candidates[longestStripIndex];
if (longestStrip.Item1.m_Faces.Count == 0)
{
separateTriangles.m_Faces.Add(currentTriangle.m_Triangle);
continue;
}
foreach (int tri in longestStrip.Item2)
{
m_Triangles[tri].m_Marked = true;
}
tStrips.Add(longestStrip.Item1);
}
if (separateTriangles.m_Faces.Count > 0)
{
tStrips.Add(separateTriangles);
}
return(tStrips);
}
Tuple <ModelBase.FaceListDef, List <int> > GetStripAndIndicesForStartingEvenEdge(
TriangleLinked start, TriangleEdge startForwardEdge)
{
List <int> stripIndices = new List <int>();
List <TriangleRotation> stripRotations = new List <TriangleRotation>();
List <TriangleLinked> linked = GetLinked(start)[(int)startForwardEdge];
TriangleLinked bestNeighbour = DetermineBestNextNeighbour(start, linked, startForwardEdge);
if (bestNeighbour == null)
{
return(new Tuple <ModelBase.FaceListDef, List <int> >(new ModelBase.FaceListDef(), new List <int>()));
}
TriangleRotation startRotation = (TriangleRotation)((int)(startForwardEdge - TriangleEdge.Edge_BC + 3) % 3);
TriangleLinked t = start;
TriangleEdge currentEdge = startForwardEdge;
TriangleRotation currentRotation = startRotation;
bool even = true;
int index_t = -1;
while (t != null && !stripIndices.Contains((index_t = m_Triangles.IndexOf(t))))
{
stripIndices.Add(index_t);
stripRotations.Add(currentRotation);
linked = GetLinked(t)[(int)currentEdge];
bestNeighbour = DetermineBestNextNeighbour(t, linked, currentEdge);
t = bestNeighbour;
even = !even;
if (t != null)
{
// Determine rotation and the edge to be used to get the next face
ModelBase.FaceDef triangleC_CW = new ModelBase.FaceDef(3);
if (even)
{
triangleC_CW.m_Vertices[0] = t.m_Triangle.m_Vertices[0];
triangleC_CW.m_Vertices[1] = t.m_Triangle.m_Vertices[1];
triangleC_CW.m_Vertices[2] = t.m_Triangle.m_Vertices[2];
}
else
{
triangleC_CW.m_Vertices[0] = t.m_Triangle.m_Vertices[2];
triangleC_CW.m_Vertices[1] = t.m_Triangle.m_Vertices[1];
triangleC_CW.m_Vertices[2] = t.m_Triangle.m_Vertices[0];
}
// The edge of the vertices which match the preceding triangle's
TriangleEdge linkBackEdge = TriangleEdge.Edge_AB;
// The vertices which match the preceding triangle's
ModelBase.VertexDef[] currentMatchedEdge = new ModelBase.VertexDef[2];
TriangleLinked previous = m_Triangles[stripIndices[stripIndices.Count - 1]];
currentMatchedEdge[0] = previous.m_Triangle.m_Vertices[(int)(currentEdge + 0) % 3];
currentMatchedEdge[1] = previous.m_Triangle.m_Vertices[(int)(currentEdge + 1) % 3];
// Find the edge in the current triangle which if odd has been made CW which matches
// that from the preceding triangle. This will be set as the current triangle's first,
// or 'AB' edge and the next edge (next two vertices) will be used to match the next
// triangle.
for (int i = 0; i < 3; i++)
{
ModelBase.VertexDef[] edge = new ModelBase.VertexDef[2];
edge[0] = triangleC_CW.m_Vertices[(i + 0) % 3];
edge[1] = triangleC_CW.m_Vertices[(i + 1) % 3];
if (edge.Except(currentMatchedEdge).Count() == 0)
{
linkBackEdge = (TriangleEdge)i;
break;
}
}
TriangleEdge nextEdgeNoC_CW = (TriangleEdge)((int)(linkBackEdge + 1) % 3);
TriangleEdge nextEdge = nextEdgeNoC_CW;
if (!even)
{
// If odd, nextEdgeNoC_CW points to the edge to be used if written CW, however
// all triangles have been read in as CCW so need to get the corresponding edge
// in CCW version.
ModelBase.VertexDef[] nextEdgeNoC_CW_Vertices = new ModelBase.VertexDef[2];
nextEdgeNoC_CW_Vertices[0] = triangleC_CW.m_Vertices[(int)(nextEdgeNoC_CW + 0) % 3];
nextEdgeNoC_CW_Vertices[1] = triangleC_CW.m_Vertices[(int)(nextEdgeNoC_CW + 1) % 3];
for (int i = 0; i < 3; i++)
{
ModelBase.VertexDef[] ccwEdge = new ModelBase.VertexDef[2];
ccwEdge[0] = t.m_Triangle.m_Vertices[(i + 0) % 3];
ccwEdge[1] = t.m_Triangle.m_Vertices[(i + 1) % 3];
if (nextEdgeNoC_CW_Vertices.Except(ccwEdge).Count() == 0)
{
nextEdge = (TriangleEdge)i;
break;
}
}
}
// Now we need to determine the required rotation of the current triangle so that for
// even triangles the new vertex in at index 0 and for odd triangles it occurs at
// index 2.
ModelBase.VertexDef uniqueVertex = t.m_Triangle.m_Vertices.Except(previous.m_Triangle.m_Vertices).ElementAt(0);
int uniqueVertexIndex = Array.IndexOf(t.m_Triangle.m_Vertices, uniqueVertex);
TriangleRotation requiredRotation =
(even) ? (TriangleRotation)((uniqueVertexIndex - 2 + 3) % 3) :
(TriangleRotation)(uniqueVertexIndex);
currentRotation = requiredRotation;
currentEdge = nextEdge;
// To best understand how this works, debug and step-through how the following model is handled:
//
// An example:
// Faces as defined in model (all Counter-Clockwise (CCW)):
// f 1 2 3
// f 4 1 3
// f 4 5 1
// Build strip from edge CA.
// # 2 3 1 (LS) <- Need to Left Shift vertices so that CA is the second edge (in a tri. strip it's
// always the second edge that's shared - see diagram at top).
// # 3 1 4 (4 1 3) <- For odd faces the new vertex must be at index [0]
// No Rot required, link-back CW: AB, CW forward: AB + 1 = BC,
// CCW forward: edge in CCW that contains vertices in (CW forward) = AB
// The next triangle is the one that shares the CCW edge AB (vertices 1 and 4)
// # 1 4 5 (RS) <- Even face the new vertex needs to be in index [2] so need to Right Shift vertices
// Repeat steps as for above face but don't need to worry about converting between CCW and CW order
}
}
ModelBase.FaceListDef tStrip = new ModelBase.FaceListDef(ModelBase.PolyListType.TriangleStrip);
for (int i = 0; i < stripIndices.Count; i++)
{
TriangleRotation requiredRotation = (TriangleRotation)stripRotations[i];
ModelBase.FaceDef rotated = new ModelBase.FaceDef(3);
rotated.m_Vertices[0] = m_Triangles[stripIndices[i]].m_Triangle.m_Vertices[((int)(0 + requiredRotation) % 3)];
rotated.m_Vertices[1] = m_Triangles[stripIndices[i]].m_Triangle.m_Vertices[((int)(1 + requiredRotation) % 3)];
rotated.m_Vertices[2] = m_Triangles[stripIndices[i]].m_Triangle.m_Vertices[((int)(2 + requiredRotation) % 3)];
tStrip.m_Faces.Add(rotated);
}
return(new Tuple <ModelBase.FaceListDef, List <int> >(tStrip, stripIndices));
}
