public double _MeanCurvature(Mesh3D m3d, int index)
{
double meanCurvature = 0.0;
double mixedArea = 0;
double barycentricArea = 0;
Vector3D normalOperator = new Vector3D();
int[] nbrs = m3d.GetNeighbourVertices(index);
HashSet <int> fi = new HashSet <int>();
for (int i = 0; i < nbrs.Length; i++)
{
int fii = m3d.FindFaceFromEdge(index, nbrs[i]);
fi.Add(fii);
}
int m = fi.Count;
int[] vLeft = null;
int[] vRight = null;
if (m > 1)
{
vLeft = m3d.Faces.ElementAt(fi.ElementAt(0));
//int[] vRight = m3d.Faces.ElementAt(fi.ElementAt((i + 1) % m));
vRight = m3d.Faces.ElementAt(fi.ElementAt(1));
}
else if (m == 1)
{
//Console.WriteLine(m+" -- "+fi.ElementAt(i) + " - " + fi.ElementAt((i + 1) % m));
vLeft = m3d.Faces.ElementAt(fi.ElementAt(0));
vRight = m3d.Faces.ElementAt(fi.ElementAt(0));
}
else
{
return(_infinity);
}
// This point is also center point.
int vertexInCommon1 = -1;
// This point is the other end of common edge between two triangles.
int vertexInCommon2 = -1;
// These two points are not shared between two triangles.
int vertexUniqueForLeftFace = -1;
int vertexUniqueForRightFace = -1;
// Find common vertexes in two adjacent triangles.
for (int j = 0; j < 3; j++)
{
for (int k = 0; k < 3; k++)
{
// If found vertex is pivotal point, save it as vertexInCommon1.
// If found vertex is not pivotal point, then this vertex is
// the other end of the common edge of two triangle. Save it as
// vertexInCommon2.
if (vLeft[j] == vRight[k])
{
if (vLeft[j] == index)
{
vertexInCommon1 = vLeft[j];
break;
}
else
{
vertexInCommon2 = vLeft[j];
break;
}
}
else
{
// If the vertex is not one of common vertexes, save it as
// vertexUniqueForLeftFace.
if (k == 2)
{
vertexUniqueForLeftFace = vLeft[j];
}
}
}
}
// If two triangles share only center point, the index point is located
// on the edge of the surface. For example, for the ucf file the margin
// of contours might not lap around, therefore the contour might have
// boundary.
if (vertexInCommon2 == -1)
{
return(_infinity);
}
// Now task is finding a vertex which is unique to right triangle.
// Go over each vertex in right face and find a vertex which is
// not shared with left triangle. then save it as
// vertexUniqueForLeftFace.
for (int l = 0; l < 3; l++)
{
if (vRight[l] == vertexInCommon1)
{
}
else if (vRight[l] == vertexInCommon2)
{
}
else
{
vertexUniqueForRightFace = vRight[l];
break;
}
}
if (vertexUniqueForLeftFace == -1)
{
vertexUniqueForLeftFace = vertexInCommon1;
}
// Obtain vector represent of vertex locations.
Point3D pivotalCommonPoint = m3d.Vertices.ElementAt(vertexInCommon1);
Point3D theOtherCommonPoint = m3d.Vertices.ElementAt(vertexInCommon2);
Point3D leftUniquePoint = m3d.Vertices.ElementAt(vertexUniqueForLeftFace);
Point3D rightUniquePoint = m3d.Vertices.ElementAt(vertexUniqueForRightFace);
Vector3D centerEdgeVector = Vector3D.Subtract(theOtherCommonPoint.ToVector3D(), pivotalCommonPoint.ToVector3D());
if (!_isAbsoluteMeanCurvature)
{
Vector3D v1 = Vector3D.Subtract(leftUniquePoint.ToVector3D(), pivotalCommonPoint.ToVector3D());
Vector3D v2 = Vector3D.Subtract(rightUniquePoint.ToVector3D(), pivotalCommonPoint.ToVector3D());
// Normal vector of the first face.
Vector3D normal1 = Vector3D.CrossProduct(v1, centerEdgeVector);
// Normal vector of the second face.
Vector3D normal2 = Vector3D.CrossProduct(centerEdgeVector, v2);
// Dihedral angle between adjacent triangular faces and is computed
// as the angle between the corresponding normals.
double dihedralAngle =
Math.Acos(Vector3D.DotProduct(normal1, normal2) /
(normal1.Length * normal2.Length));
// Edge is convex edge if the edge type is greater than 0, and edge
// is concave edge if the edge type is smaller than 0, and edge is
// planner if edge type is 0;
double edgeType =
Vector3D.DotProduct(
Vector3D.CrossProduct(normal1, normal2), centerEdgeVector);
double edgeVectorEuclideanNorm = centerEdgeVector.Length;
if (edgeType < 0)
{
meanCurvature += -1 * edgeVectorEuclideanNorm * dihedralAngle;
}
else if (edgeType > 0)
{
meanCurvature += edgeVectorEuclideanNorm * dihedralAngle;
}
else
{
meanCurvature += 0;
}
}
// Calculate cot x and cot y where x and y are the angles opposite
// common edge in two incident triangles.
try
{
double angleAlpha = Vector3D.AngleBetween(pivotalCommonPoint.ToVector3D(), leftUniquePoint.ToVector3D());
//theOtherCommonPoint.ToVector3D()));
double angleBetha = Vector3D.AngleBetween(pivotalCommonPoint.ToVector3D(), rightUniquePoint.ToVector3D());
//,theOtherCommonPoint);
// angleAlpha, angleTheta, and angleOmega are three angles of left triangles.
// Test if any of these angles is obtuse.
double angleTheta = Vector3D.AngleBetween(leftUniquePoint.ToVector3D(),
pivotalCommonPoint.ToVector3D());
//,theOtherCommonPoint);
double angleOmega = Vector3D.AngleBetween(leftUniquePoint.ToVector3D(),
theOtherCommonPoint.ToVector3D());
//,pivotalCommonPoint);
// Obtain Mean Curvature Normal Operator.
double cotAlpha = 1 / Math.Tan(angleAlpha);
double cotBetha = 1 / Math.Tan(angleBetha);
double scalar = (cotAlpha + cotBetha);
Vector3D centerEdgeVectorScalarMultiplied = Vector3D.Multiply(centerEdgeVector, scalar);
normalOperator = Vector3D.Add(normalOperator, centerEdgeVectorScalarMultiplied);
// Calculate area of the left triangle.
Vector3D leftEdgeVector = Vector3D.Subtract(pivotalCommonPoint.ToVector3D(), leftUniquePoint.ToVector3D());
double magnitudeOfLeftEdge = leftEdgeVector.Length;
Vector3D rightEdgeVector = Vector3D.Subtract(theOtherCommonPoint.ToVector3D(), leftUniquePoint.ToVector3D());
double magnitudeOfRightEdge = rightEdgeVector.Length;
double areaOfLeftTriangle =
Math.Sin(angleAlpha) * magnitudeOfLeftEdge * magnitudeOfRightEdge / 2.0;
if (_areaCalMethod == BARYCENTRIC_AREA)
{
barycentricArea = barycentricArea + areaOfLeftTriangle / 3.0;
}
else if (_areaCalMethod == VORONOI_AREA)
{
// Obtuse angle exists at pivot vertex.
if (angleTheta > Math.PI / 2)
{
mixedArea = mixedArea + areaOfLeftTriangle / 2.0;
}
// Obtuse angle exists at other vertex beside the pivot vertex.
else if (angleAlpha > Math.PI / 2 || angleOmega > Math.PI / 2)
{
mixedArea = mixedArea + areaOfLeftTriangle / 4.0;
}
// No obtuse angle exists
else
{
double magnitudeOfCenterVector = centerEdgeVector.Length;
double voronoiAreaInATriangle = magnitudeOfLeftEdge *
magnitudeOfLeftEdge * (1 / Math.Tan(angleOmega)) +
magnitudeOfCenterVector * magnitudeOfCenterVector *
(1 / Math.Tan(angleAlpha));
mixedArea = mixedArea + voronoiAreaInATriangle / 8.0;
}
}
}
catch (Exception ige)
{
Console.WriteLine(
"Unable to calculate curvature of face # " + index +
" Reason " + ige.Message);
}
if (_areaCalMethod == BARYCENTRIC_AREA)
{
normalOperator = Vector3D.Multiply(normalOperator, 1.0 / (2.0 * barycentricArea));
meanCurvature = meanCurvature * (1.0 / (4.0 * barycentricArea));
}
else if (_areaCalMethod == VORONOI_AREA)
{
normalOperator = Vector3D.Multiply(normalOperator, 1.0 / (2.0 * mixedArea));
meanCurvature = meanCurvature * (1.0 / (4.0 * mixedArea));
}
double curvature = meanCurvature;
if (_isAbsoluteMeanCurvature)
{
// The mean curvature value is half of the magnitude of Normal Operator.
curvature = normalOperator.Length / 2;
}
return(meanCurvature);
}
internal MeshGeometry3D AutoSnake(MeshGeometry3D mesh, ref MeshBuilder newmbP)
{
//Dictionary<Int32, SmileEdge> neighbours = SmileVisual3D.findNeighbours(mesh);
Point3DCollection positions = mesh.Positions;
Int32Collection triangleIndices = mesh.TriangleIndices;
Mesh3D m3d = new Mesh3D(positions, triangleIndices);
Vector3DCollection t = new Vector3DCollection(positions.Count);
Vector3DCollection b = new Vector3DCollection(positions.Count);
Vector3DCollection n = new Vector3DCollection(positions.Count);
double eThreshold = -0.5;
double nThreshold = 0.8;
double minEnergy = 10;
double alpha = 1;
double betha = 1;
double ballon = 1;
double lambda = 1;
Vector3DCollection e = new Vector3DCollection(positions.Count);
Vector3DCollection eInt = new Vector3DCollection(positions.Count);
Vector3DCollection eExt = new Vector3DCollection(positions.Count);
Vector3DCollection delta = new Vector3DCollection(positions.Count);
Vector3DCollection f = new Vector3DCollection(positions.Count);
Vector3DCollection tETF = new Vector3DCollection(positions.Count);
//Vector3DCollection k = new Vector3DCollection();
//DoubleCollection kH = new DoubleCollection();
Dictionary <int, Double> kH = new Dictionary <int, double>();
MeshBuilder newmbD = new MeshBuilder(false, false);
for (int i = 0; i < triangleIndices.Count; i += 3)
{
for (int a = 0; a < 3; a++)
{
int vi = triangleIndices[i + a];
if (!kH.ContainsKey(vi))
{
double kHi = _MeanCurvature(m3d, vi);
kH.Add(vi, kHi);
}
//Console.WriteLine("start mean");
//kH.Add(kHi);
//Console.WriteLine("end mean");
if (a == 2)
{
int vi1 = triangleIndices[i + a - 1];
int vi2 = triangleIndices[i + a - 2];
double kH3 = 0;
kH.TryGetValue(vi, out kH3);
double kH2 = 0;
kH.TryGetValue(vi1, out kH2);
double kH1 = 0;
kH.TryGetValue(vi2, out kH1);
if ((kH3 < eThreshold || kH2 < eThreshold || kH1 < eThreshold))
{
newmbD.Positions.Add(positions[vi]);
newmbD.Positions.Add(positions[vi1]);
newmbD.Positions.Add(positions[vi2]);
newmbD.TriangleIndices.Add(i + a);
newmbD.TriangleIndices.Add(i + a - 1);
newmbD.TriangleIndices.Add(i + a - 2);
}
if ((kH3 > nThreshold || kH2 > nThreshold || kH1 > nThreshold))
{
newmbP.Positions.Add(positions[vi]);
newmbP.Positions.Add(positions[vi1]);
newmbP.Positions.Add(positions[vi2]);
newmbP.TriangleIndices.Add(i + a);
newmbP.TriangleIndices.Add(i + a - 1);
newmbP.TriangleIndices.Add(i + a - 2);
}
}
int[] nbrs = m3d.GetNeighbourVertices(vi);
Vector3DCollection N = new Vector3DCollection(positions.Count);
Point3D pi = positions[vi];
int i0 = triangleIndices[i + a];
if (i + a - 1 >= 0)
{
i0 = triangleIndices[i + a - 1];
}
Point3D pi0 = positions[i0];
int i1 = vi;
if (i + a + i < triangleIndices.Count)
{
i1 = triangleIndices[i + a + 1];
}
Point3D pi1 = positions[i1];
t.Insert(vi, (pi1 - pi0) / (Point3D.Subtract(pi1, pi0).Length));
//t[i] = (pi1 - pi0) / Math.Sqrt((Point3D.Subtract(pi1, pi0).Length));
n.Insert(vi, SmileVisual3D.CalculateNormal(pi0, pi, pi1));
b.Insert(vi, Vector3D.CrossProduct(t[vi], n[vi]));
Vector3D eIntV = new Vector3D(); //eInt[vi];
Vector3D eExtV = new Vector3D(); //eExt[vi];
Vector3D eV = new Vector3D(); //e[vi];
Vector3D sumDeltaNbrs = new Vector3D();
Vector3D sumFNbrs = new Vector3D();
int maxNbrs = (nbrs.Length > 2 ? 2 : nbrs.Length);
for (int j = 0; j < maxNbrs; j++)
{
Point3D nbj = positions[nbrs[j]];
N.Add(nbj.ToVector3D());
}
double determinantVi = determinant(N);
double kv = 0;
kH.TryGetValue(vi, out kv);
double jminEnergy = minEnergy;
Point3D tempNbj = pi;
for (int j = 0; j < maxNbrs; j++)
{
Point3D nbj = positions[nbrs[j]];
double ku = 0;
kH.TryGetValue(nbrs[j], out ku);
sumDeltaNbrs += Vector3D.Multiply((kv - ku), Vector3D.Divide(Point3D.Subtract(nbj, pi), (Point3D.Subtract(nbj, pi).Length)));
delta.Insert(vi, (1 / determinantVi) * sumDeltaNbrs);
f.Insert(vi, Vector3D.Multiply((1 - lambda), Vector3D.Multiply((1 / determinantVi), new Vector3D())) + Vector3D.Multiply(lambda, delta[vi]));
double eIntj = alpha * (Point3D.Subtract(pi0, nbj).Length) + betha * (Point3D.Subtract(pi0, Point3D.Add(pi1, (Vector3D)nbj)).Length); //TODO: crosscheck
double eFaej = ballon * (-(f[vi].Length) - Vector3D.DotProduct((f[vi] / f[vi].Length), (Point3D.Subtract(nbj, pi) / Point3D.Subtract(nbj, pi).Length))); //TODO: crosscheck
double ePressj = ballon * Vector3D.DotProduct(b[vi], (Point3D.Subtract(pi0, nbj) / Point3D.Subtract(pi0, nbj).Length));
double eExtj = eFaej + ePressj;
double ej = eIntj + eExtj;
if (j == 0)
{
eIntV.X = eIntj;
eExtV.X = eExtj;
eV.X = ej;
}
if (j == 1)
{
eIntV.Y = eIntj;
eExtV.Y = eExtj;
eV.Y = ej;
}
if (j == 2)
{
eIntV.Z = eIntj;
eExtV.Z = eExtj;
eV.Z = ej;
}
if (ej < jminEnergy)
{
jminEnergy = ej;
tempNbj = nbj;
//TODO: snake movement
//AddSnakeElement(nbj);
}
}
AddSnakeElement(tempNbj);
eInt.Insert(vi, eIntV);
eExt.Insert(vi, eExtV);
e.Insert(vi, eV);
//delta.Insert(vi, (1 / determinant(N[vi])) * sumDeltaNbrs); //TODO:implemenet
//f.Insert(vi, n[vi]);// (1 - lambda) * (1 / (Math.Abs(nbrs.Count))) + lambda *delta[i]; //TODO:implemenet
tETF.Insert(vi, Vector3D.CrossProduct(delta[vi], n[vi]));
}
}
return(newmbD.ToMesh());
/*
* for (int i = 0; i < positions.Count; i++)
* {
* Int32Collection nbrs = neighbours[i].neighbours;
*
* Point3D pi = positions[i];
* int i0 = i;
* if (i - 1 >= 0) i0 = i - 1;
* Point3D pi0 = positions[i0];
* int i1 = i;
* if (i + i < triangleIndices.Count) i = i + 1;
* Point3D pi1 = positions[i1];
*
* t[i] = (pi1 - pi0) / (Point3D.Subtract(pi1, pi0).Length);
* //t[i] = (pi1 - pi0) / Math.Sqrt((Point3D.Subtract(pi1, pi0).Length));
* n[i] = SmileVisual3D.CalculateNormal(pi0, pi, pi1);
* b[i] = Vector3D.CrossProduct(t[i], n[i]);
*
*
* Vector3D eIntV = eInt[i];
* Vector3D eExtV = eExt[i];
* Vector3D eV = e[i];
* int maxNbrs = (nbrs.Count > 2 ? 2 : nbrs.Count);
* for (int j = 0; j < maxNbrs; j++)
* {
* Point3D nbj = positions[nbrs[j]];
* double eIntj = alpha * (Point3D.Subtract(pi0, nbj).Length) + betha * (Point3D.Subtract(pi0, Point3D.Add(pi1, (Vector3D)nbj)).Length); //TODO: crosscheck
*
*
* delta[i] = n[i];// 1 / determinant(N[i]); //TODO:implemenet
* f[i] = n[i];// (1 - lambda) * (1 / (Math.Abs(nbrs.Count))) + lambda *delta[i]; //TODO:implemenet
*
*
* double eFaej = ballon * (-(f[i].Length) - Vector3D.DotProduct((f[i] / f[i].Length), (Point3D.Subtract(nbj, pi) / Point3D.Subtract(nbj, pi).Length))); //TODO: crosscheck
* double ePressj = ballon * Vector3D.DotProduct(b[i], (Point3D.Subtract(pi0, nbj) / Point3D.Subtract(pi0, nbj).Length));
* double eExtj = eFaej + ePressj;
* double ej = eIntj + eExtj;
*
* if (j == 0)
* {
* eIntV.X = eIntj;
* eExtV.X = eExtj;
* eV.X = ej;
* }
* if (j == 1)
* {
* eIntV.Y = eIntj;
* eExtV.Y = eExtj;
* eV.Y = ej;
* }
* if (j == 2)
* {
* eIntV.Z = eIntj;
* eExtV.Z = eExtj;
* eV.Z = ej;
* }
*
* if (ej < minEnergy)
* {
* minEnergy = ej;
* //TODO: snake movement
* AddSnakeElement(nbj);
* }
*
* eInt[i] = eIntV;
* eExt[i] = eExtV;
* e[i] = eV;
* }
*
* tETF[i] = Vector3D.CrossProduct(delta[i], n[i]);
*
* }
* */
}
public double __MeanCurvature(Mesh3D m3d, int verticeIndex)
{
return(0);
/*
* // Initializing all necessary local variables.
* double meanCurvature = 0.0;
* double mixedArea = 0;
* double barycentricArea = 0;
* Vector3D normalOperator = new Vector3D();
* //double[] normalOperator = new double[3];
*
* //for(int i=0; i<3; i++){
* // normalOperator[i] = 0.0;
* //}
*
* // no neighbors of this face.
* if(nbrs == null){
* return _infinity;
* }
*
* // If the index point is connected with only one triangle, the index point
* // is located on the edge of the surface. For example, for the ucf file the
* // margin of contours might not lap around, therefore the contour might have
* // boundary.
* if(nbrs.Count== 1){
* return _infinity;
* }
*
*
* // Orientation Specification:
* // Look at surface from outside such a way that the pivotal vertex is
* // located upward. Then I call a triangle in the left is left triangle
* // and the other triangle in the right is right triangle.
* //
* // Up pivotal vertex
* // *
* // * * *
* // * * *
* // * * *
* // * * * * * * * *
* // Left Right
* // Down
* //
* //
* // 1. Absolute Mean Curvature Computation Algorithm Summary:
* // Xo - pivot vertex
* // X1,..,Xj,..,Xn - the first ring neighbor vertices of the vertex o.
* // n - number of the first ring neighbor vertices of the vertex o.
* //
* // Xo
* // * * * * o
* // * * * * * * *
* // * * * * * * *
* // * * * * O * * * * Xj+1 Xj-1 * Aoj * Boj* Xj+1
* // * * * * * * *
* // * * * * * * *
* // * * * * *
* // Xj-1 Xj Xj
* //
* // Aoj is angle at the vertex Xj-1
* // Boj is angle at the vertex Xj+1
* //
* //
* // Mean Curvature Normal Operator is calculated by following 2 steps:
* // First, calculate summation of (cot Aoj + cot Boj)(Xo - Xj) over j
* // from 1 to n, where Xo is the pivot vertex and Xj's are elements of
* // first ring neighbors vertices of the pivot vertex.
* // Second, divide above value by 2*AreaMixed.
* //
* // Area Mixed can be calculated by either Barycentric method or
* // Voronoi method.
* // 1. Barycentric method calculate AreaMixed by adding one third of each
* // triangle area.
* //
* // 2. Voronoi method is following
* // if there is obtuse angle at pivot vertex, add half of the triangle
* // area.
* // else if there is obtuse angle beside pivot vertex, add one fourth of
* // triangle area.
* // else if there is no obtuse angle, add Voronoi area of triangle.
* //
* // Finally the Mean Curvature value is computed by taking half of the
* // magnitude of the Mean Curvature Normal Operator.
*
* // 2. Mean Curvature Computation Algorithm Summary: The mean curvature
* // (non absolute mean curvature) is computed as a summation over the
* // edges adjacent to a vertex of the angle between the faces adjacent to
* // the edge multiplied by the edge length, and divided by four times the
* // area associated with the vertex.
*
*
*
* // Go over two neighbor faces which are connected to pivotal point
* // and which share an edge between.
* for (int i = 0; i < nbrs.Count; i++) {
*
* // Obtain vertices which are consist of faces.
* Point3D vertiesInLeftFace = points[nbrs[i]];
* Point3D vertiesInRightFace = points[nbrs[i]];
*
* if (i + 1 == nbrs.Count)
* {
* vertiesInRightFace = points[nbrs[0]];
* }
* else{
* vertiesInRightFace = points[nbrs[i+1]];
* }
*
* // This point is also center point.
* int vertexInCommon1 = -1;
*
* // This point is the other end of common edge between two triangles.
* int vertexInCommon2 = -1;
*
* // These two points are not shared between two triangles.
* int vertexUniqueForLeftFace = -1;
* int vertexUniqueForRightFace = -1;
*
* // Find common vertexes in two adjacent triangles.
* for(int j=0; j<3; j++){
* for(int k=0; k<3; k++){
*
* // If found vertex is pivotal point, save it as vertexInCommon1.
* // If found vertex is not pivotal point, then this vertex is
* // the other end of the common edge of two triangle. Save it as
* // vertexInCommon2.
* if(vertiesInLeftFace[j] == vertiesInRightFace[k]){
* if(vertiesInLeftFace[j] == index){
* vertexInCommon1 = vertiesInLeftFace[j];
* break;
* }
* else{
* vertexInCommon2 = vertiesInLeftFace[j];
* break;
* }
* }
* else{
* // If the vertex is not one of common vertexes, save it as
* // vertexUniqueForLeftFace.
* if(k==2){
* vertexUniqueForLeftFace = vertiesInLeftFace[j];
* }
* }
* }
* }
*
* // If two triangles share only center point, the index point is located
* // on the edge of the surface. For example, for the ucf file the margin
* // of contours might not lap around, therefore the contour might have
* // boundary.
* if(vertexInCommon2 == -1){
* return _infinity;
* }
*
* // Now task is finding a vertex which is unique to right triangle.
* // Go over each vertex in right face and find a vertex which is
* // not shared with left triangle. then save it as
* // vertexUniqueForLeftFace.
* for(int l=0; l<3; l++){
* if(vertiesInRightFace[l] == vertexInCommon1 ){
* }
* else if(vertiesInRightFace[l] == vertexInCommon2){
* }
* else{
* vertexUniqueForRightFace = vertiesInRightFace[l];
* break;
* }
* }
*
* // Obtain vector represent of vertex locations.
* double[] pivotalCommonPoint = new double[_dimension];
* double[] theOtherCommonPoint = new double[_dimension];
* double[] leftUniquePoint = new double[_dimension];
* double[] rightUniquePoint = new double[_dimension];
*
* for(int dim=0; dim<_dimension; dim++){
*
* pivotalCommonPoint[dim] = _points.getPoint(vertexInCommon1)[dim];
* theOtherCommonPoint[dim] = _points.getPoint(vertexInCommon2)[dim];
* leftUniquePoint[dim] = _points.getPoint(vertexUniqueForLeftFace)[dim];
* rightUniquePoint[dim] = _points.getPoint(vertexUniqueForRightFace)[dim];
* }
*
* double[] centerEdgeVector =
* VectorMathDouble.difference(theOtherCommonPoint, pivotalCommonPoint);
*
* if(!_isAbsoluteMeanCurvature){
*
* // The mean curvature (non absolute mean curvature) is computed as a
* // summation over the edges adjacent to a vertex of the angle between
* // the faces adjacent to the edge multiplied by the edge length, and
* // divided by four times the area associated with the vertex.
*
* // Reference:
* // Anupama Jagannathan, "Segmentation and Recognition of 3D Point Clouds
* // within Graph-theoretic and Thermodynamic Frameworks.", the Department
* // of Electrical and Computer Engineering, 61-62, 2005.
* // http://www.ece.neu.edu/faculty/elmiller/laisir/pdfs/jagannathan_phd.pdf
*
* // Seungbum Koo, Kunwoo Lee, "Wrap-around operation to make
* // multi-resolution model of part and assembly.", department of Machanical
* // and Aerospace Engineering, Seoul National University, 3, 2002,
* // http://www.ece.tufts.edu/~elmiller/laisr/pdfs/jagannathan_phd.pdf.
*
* double[] v1 = VectorMathDouble.difference(leftUniquePoint, pivotalCommonPoint);
* double[] v2 = VectorMathDouble.difference(rightUniquePoint, pivotalCommonPoint);
*
* // Normal vector of the first face.
* double[] normal1 = VectorMathDouble.cross(v1, centerEdgeVector);
*
* // Normal vector of the second face.
* double[] normal2 = VectorMathDouble.cross(centerEdgeVector, v2);
*
* // Dihedral angle between adjacent triangular faces and is computed
* // as the angle between the corresponding normals.
* double dihedralAngle =
* Math.acos(VectorMathDouble.dot(normal1, normal2)/
* (VectorMathDouble.magnitude(normal1)*VectorMathDouble.magnitude(normal2)));
*
* // Edge is convex edge if the edge type is greater than 0, and edge
* // is concave edge if the edge type is smaller than 0, and edge is
* // planner if edge type is 0;
* double edgeType =
* VectorMathDouble.dot(
* VectorMathDouble.cross(normal1, normal2), centerEdgeVector);
*
* double edgeVectorEuclideanNorm =
* VectorMathDouble.magnitude(centerEdgeVector);
*
* if(edgeType < 0){
* meanCurvature += -1*edgeVectorEuclideanNorm*dihedralAngle;
* }
* else if(edgeType > 0){
* meanCurvature += edgeVectorEuclideanNorm*dihedralAngle;
* }
* else{
* meanCurvature += 0;
* }
* }
*
* // Calculate cot x and cot y where x and y are the angles opposite
* // common edge in two incident triangles.
* try {
*
* double angleAlpha = VectorMathDouble.vectorAngle(pivotalCommonPoint,
* leftUniquePoint,
* theOtherCommonPoint);
*
* double angleBetha = VectorMathDouble.vectorAngle(pivotalCommonPoint,
* rightUniquePoint,
* theOtherCommonPoint);
*
* // angleAlpha, angleTheta, and angleOmega are three angles of left triangles.
* // Test if any of these angles is obtuse.
* double angleTheta = VectorMathDouble.vectorAngle(leftUniquePoint,
* pivotalCommonPoint,
* theOtherCommonPoint);
* double angleOmega = VectorMathDouble.vectorAngle(leftUniquePoint,
* theOtherCommonPoint,
* pivotalCommonPoint);
*
* // Obtain Mean Curvature Normal Operator.
* double cotAlpha = 1/Math.tan(angleAlpha);
* double cotBetha = 1/Math.tan(angleBetha);
* double scalar = (cotAlpha + cotBetha);
* double[] centerEdgeVectorScalarMultiplied =
* VectorMathDouble.multiply(centerEdgeVector, scalar);
*
* normalOperator =
* VectorMath.add(normalOperator, centerEdgeVectorScalarMultiplied);
*
* // Calculate area of the left triangle.
* double[] leftEdgeVector = VectorMathDouble.difference(pivotalCommonPoint,
* leftUniquePoint);
* double magnitudeOfLeftEdge = VectorMathDouble.magnitude(leftEdgeVector);
*
* double[] rightEdgeVector = VectorMathDouble.difference(theOtherCommonPoint,
* leftUniquePoint);
* double magnitudeOfRightEdge = VectorMathDouble.magnitude(rightEdgeVector);
*
* double areaOfLeftTriangle =
* Math.sin(angleAlpha)*magnitudeOfLeftEdge*magnitudeOfRightEdge/2.0;
*
* if(_areaCalMethod == BARYCENTRIC_AREA){
* barycentricArea = barycentricArea + areaOfLeftTriangle/3.0;
* }
* else if(_areaCalMethod == VORONOI_AREA){
* // Obtuse angle exists at pivot vertex.
* if(angleTheta > Math.PI/2){
* mixedArea = mixedArea + areaOfLeftTriangle/2.0;
* }
* // Obtuse angle exists at other vertex beside the pivot vertex.
* else if(angleAlpha > Math.PI/2 || angleOmega > Math.PI/2){
* mixedArea = mixedArea + areaOfLeftTriangle/4.0;
* }
* // No obtuse angle exists
* else{
* double magnitudeOfCenterVector = VectorMathDouble.magnitude(centerEdgeVector);
*
* double voronoiAreaInATriangle = magnitudeOfLeftEdge*
* magnitudeOfLeftEdge*
* (1/Math.tan(angleOmega)) +
* magnitudeOfCenterVector*
* magnitudeOfCenterVector*
* (1/Math.tan(angleAlpha));
*
* mixedArea = mixedArea + voronoiAreaInATriangle/8.0;
* }
* }
* }
* catch (InappropriateGeometryException ige) {
* throw new CalculationException(
* "Unable to calculate curvature of face # " +i +
* " Reason " + ige.getMessage());
* }
* }
*
* if(_areaCalMethod == BARYCENTRIC_AREA){
* normalOperator = VectorMathDouble.multiply(normalOperator, 1.0/(2.0*barycentricArea));
* meanCurvature = meanCurvature*(1.0/(4.0*barycentricArea));
* }
* else if(_areaCalMethod == VORONOI_AREA){
*
* normalOperator = VectorMathDouble.multiply(normalOperator, 1.0/(2.0*mixedArea));
* meanCurvature = meanCurvature*(1.0/(4.0*mixedArea));
* }
*
* double curvature = meanCurvature;
*
* if(_isAbsoluteMeanCurvature){
*
* // The mean curvature value is half of the magnitude of Normal Operator.
* curvature = VectorMath.magnitude(normalOperator) / 2;
* }
*
* return curvature;
* */
}
