/// <summary>
/// Pass in a cloud of points and an array of triangle indices shall be returned.
/// </summary>
/// <param name="points">Points to create hull from.</param>
/// <returns>Triangle index array of hull.</returns>
public static int[] ComputeHull(Vector3[] points)
{
if (points.Length < 3) return null;
//local copy of the point set
Face.points = points;
//calculates the first convex tetrahedron
//creates a face with the first 3 vertices
Face faceA = new Face(0, 1, 2);
//this is the center of the tetrahedron, all face should point outwards:
//they should not be visible to the centroid
Vector3 v = Centroid(points, 3, faceA);
if (faceA.IsVisible(v))
{
faceA.Flip();
}
Face face0 = new Face(3, faceA.i0, faceA.i1);
if (face0.IsVisible(v))
{
face0.Flip();
}
Face face1 = new Face(3, faceA.i1, faceA.i2);
if (face1.IsVisible(v))
{
face1.Flip();
}
Face face2 = new Face(3, faceA.i2, faceA.i0);
if (face2.IsVisible(v))
{
face2.Flip();
}
//store the tetrahedron faces in the valid faces list
validFaces = new List<Face> { faceA, face0, face1, face2 };
visibleFaces = new List<Face>(points.Length);
tmpFaces = new List<Face>(points.Length);
//so as we have a convex tetrahedron, we can skip the first 4 points
for (int i = 4; i < points.Length; i++)
{
//for each avaiable vertices
v = points[i];
//checks the point's visibility from all faces
visibleFaces.Clear();
for (int j = 0; j < validFaces.Count; j++)
{
if (validFaces[j].IsVisible(v))
{
visibleFaces.Add(validFaces[j]);
}
}
//the vertex is not visible : it is inside the convex hull, keep on
if (visibleFaces.Count == 0) continue;
//the vertex is outside the convex hull
//delete all visible faces from the valid List
for (int index = 0; index < visibleFaces.Count; index++)
{
validFaces.Remove(visibleFaces[index]);
}
//special case : only one face is visible
//it's ok to create 3 faces directly for they won't enclose any other point
if (visibleFaces.Count == 1)
{
faceA = visibleFaces[0];
validFaces.Add(new Face(i, faceA.i0, faceA.i1));
validFaces.Add(new Face(i, faceA.i1, faceA.i2));
validFaces.Add(new Face(i, faceA.i2, faceA.i0));
continue;
}
if (visibleFaces.Count > 2000)
{
Debug.LogWarning("Visible faces is too big, " + visibleFaces.Count + " cancelling operation.");
return new int[0];
}
//creates all possible new faces from the visibleFaces
tmpFaces.Clear();
for (int k = 0; k < visibleFaces.Count; k++)
{
tmpFaces.Add(new Face(i, visibleFaces[k].i0, visibleFaces[k].i1));
tmpFaces.Add(new Face(i, visibleFaces[k].i1, visibleFaces[k].i2));
tmpFaces.Add(new Face(i, visibleFaces[k].i2, visibleFaces[k].i0));
}
if (tmpFaces.Count > 8000)
{
Debug.LogWarning("Temp faces is too big, " + tmpFaces.Count + " cancelling operation.");
return new int[0];
}
//Face other;
for (int l = 0; l < tmpFaces.Count; l++)
{
Face face = tmpFaces[l];
//search if there is a point in front of the face :
//this means the face doesn't belong to the convex hull
for (int index1 = 0; index1 < tmpFaces.Count; index1++)
{
if (face != tmpFaces[index1])
{
if (face.IsVisible(tmpFaces[index1].Centroid))
{
face = null;
break;
}
}
}
//the face has no point in front of it
if (face != null)
{
validFaces.Add(face);
}
}
}
var result = new int[validFaces.Count * 3];
int vertIndex = 0;
for (int i = 0; i < validFaces.Count; i++)
{
result[vertIndex++] = validFaces[i].i0;
result[vertIndex++] = validFaces[i].i1;
result[vertIndex++] = validFaces[i].i2;
}
return result;
}
private static Vector3 Centroid(Vector3[] points, int index, Face face)
{
Vector3 p = points[index];
p += points[face.i0];
p += points[face.i1];
p += points[face.i2];
return p / 4;
}