public static void GenIntersection(
CuttingPlane plane,
Vector3 a, Vector3 b, Vector3 c,
RingGenerator rings
)
{
// find intersection vertices
Vector3 e = plane.Intersection(a, c, Vector2.zero, Vector2.zero, 0).Item1,
d = plane.Intersection(b, c, Vector2.zero, Vector2.zero, 0).Item1;
// if e == d, the three vertices lie in a line,
// and thus do not make up a triangle
if (e == d)
{
return;
// not sure if this is nescessary
throw MeshUtilsException.ZeroAreaTriangle();
}
// find proper direction for ring
Vector3 tri_nor = Vector3.Cross(c - a, c - b);
bool dir = Vector3.Dot(e - d, Vector3.Cross(plane.normal, tri_nor)) > 0;
// add connected pair in ring generator
rings.AddConnected(dir?e:d, dir?d:e);
}
public static void GenPartialTriangles(
CuttingPlane plane,
MeshPart part,
Vector3 a, Vector3 b, Vector3 c,
Vector2 txa, Vector2 txb, Vector2 txc,
int i_a, int i_b, int i_c,
HashSet <Vector3> allow_cut,
bool addUVs
)
{
// find intersection vertices / uvs
var es = plane.Intersection(a, c, txa, txc, 0);
var ds = plane.Intersection(b, c, txb, txc, 0);
Vector3 e = es.Item1, d = ds.Item1;
Vector2 txe = es.Item2, txd = ds.Item2;
// if e == d, the three vertices lie in a line,
// and thus do not make up a triangle
if (e == d)
{
return;
// not sure if this is nescessary
throw MeshUtilsException.ZeroAreaTriangle();
}
if (
!allow_cut.Contains(e) &&
!allow_cut.Contains(d)
)
{
// triangle must not be cut
part.indices.Add(part.indexMap[i_a]);
part.indices.Add(part.indexMap[i_b]);
part.indices.Add(part.indexMap[i_c]);
return;
}
// new indices
int i0 = part.vertices.Count, i1 = part.vertices.Count + 2;
// add new vertices and uvs
part.vertices.Add(d);
part.vertices.Add(e);
part.vertices.Add(d);
part.vertices.Add(e);
if (addUVs)
{
part.uvs.Add(txd);
part.uvs.Add(txe);
part.uvs.Add(txd);
part.uvs.Add(txe);
}
// generate triangles ...
// add a,d,e
part.indices.Add(part.indexMap[i_a]);
part.indices.Add(i0);
part.indices.Add(i0 + 1);
// add a,b,d
part.indices.Add(part.indexMap[i_a]);
part.indices.Add(part.indexMap[i_b]);
part.indices.Add(i0);
// add e,d,c
part.indices.Add(i1 + 1);
part.indices.Add(i1);
part.indices.Add(part.indexMap[i_c]);
}
// ------------------------------------------------------------
// Generate single triangle for an intersecting triangle a,b,c
// It is assumed that a is on the positive half plane
// ------------------------------------------------------------
public static void GenTriangle(
CuttingPlane plane,
MeshPart pos,
Vector3 a, Vector3 b, Vector3 c,
Vector2 txa, Vector2 txb, Vector2 txc,
Vector3 na, Vector3 nb, Vector3 nc,
int i_a, int i_b, int i_c,
RingGenerator rings,
bool addUVs,
bool addNormals,
float shift
)
{
// find intersection vertices / uvs
var es = plane.Intersection(c, a, txa, txc, nc, na, shift);
var ds = plane.Intersection(b, a, txb, txc, nb, na, shift);
Vector3 e = es.Item1, d = ds.Item1;
Vector2 txe = es.Item2, txd = ds.Item2;
Vector3 ne = es.Item3, nd = ds.Item3;
// if e == d, the three vertices lie in a line,
// and thus do not make up a triangle
if (e == d)
{
return;
// not sure if this is nescessary
throw MeshUtilsException.ZeroAreaTriangle();
}
// new indices
int i0 = pos.vertices.Count;
// add connected pair in ring generator
// find proper direction for ring
Vector3 tri_nor = Vector3.Cross(c - a, c - b);
bool dir = Vector3.Dot(e - d, Vector3.Cross(plane.normal, tri_nor)) > 0;
rings.AddConnected(dir?e:d, dir?d:e);
// add new vertices and uvs
pos.vertices.Add(d);
pos.vertices.Add(e);
if (addUVs)
{
pos.uvs.Add(txd);
pos.uvs.Add(txe);
}
if (addNormals)
{
pos.normals.Add(nd);
pos.normals.Add(ne);
}
// add a,d,e to positive indicies
pos.indices.Add(pos.indexMap[i_a]);
pos.indices.Add(i0);
pos.indices.Add(i0 + 1);
}
