/// <summary>
/// Generate the dual of this geometry. ( The dual mesh translates vertices to faces, and faces to vertices ).
/// Used for rendering the world.
/// </summary>
/// <typeparam name="AltVertex">The dual's vertex format</typeparam>
/// <param name="colorProvider">A system for coloring the vertices of the dual</param>
/// <returns></returns>
public Geometry <AltVertex> GenerateDual <AltVertex>(IColorProvider colorProvider) where AltVertex : struct, IVertex
{
// For each edge,
// get centroids of triangles each side
// make 2 new triangles from verts of edge + centroids
List <AltVertex> newVerts = new List <AltVertex>(mesh.vertices.Length + Topology.Edges.Count * 2);
// Initialize the first V verts
for (int i = 0; i < mesh.vertices.Length; ++i)
{
newVerts.Add(new AltVertex());
}
List <uint> newIndices = new List <uint>();
foreach (var iter in Topology.Edges)
{
Int64 key = iter.Key;
int index1 = (int)(key & 0xffffffff);
int index2 = (int)((key >> 32) & 0xffffffff);
Edge e = iter.Value;
Vector3 centroid1 = Topology.Centroids[e.triangle1].position;
Vector3 centroid2 = Topology.Centroids[e.triangle2].position;
// To find which order of vertices to use;
// if triangle1 contains index1 followed by index2,
// new tris are index1, c2, c1; index2, c1, c2
// otherwise, the opposite order.
bool edgeOrderIsAnticlockwise = false;
for (int i = 0; i < 3; i++)
{
if (indices[e.triangle1 * 3 + i] == index1)
{
if (indices[e.triangle1 * 3 + (i + 1) % 3] == index2)
{
edgeOrderIsAnticlockwise = true;
}
break;
}
}
// Get the color of the face from the color provider for the vertex in the primary mesh
Vector4 c1 = colorProvider.GetColor(index1);
Vector4 c2 = colorProvider.GetColor(index2);
if (edgeOrderIsAnticlockwise)
{
AddTriangle2(ref newVerts, ref newIndices, index1, ref centroid2, ref centroid1, c1);
AddTriangle2(ref newVerts, ref newIndices, index2, ref centroid1, ref centroid2, c2);
}
else
{
AddTriangle2(ref newVerts, ref newIndices, index1, ref centroid1, ref centroid2, c1);
AddTriangle2(ref newVerts, ref newIndices, index2, ref centroid2, ref centroid1, c2);
}
}
var newMesh = new Mesh <AltVertex>(newVerts.ToArray());
var newGeom = new Geometry <AltVertex>(newMesh, newIndices.ToArray());
return(newGeom);
}
public void TweakTriangles(float ratio, Random rand)
{
NeedsUpdate = true;
// Assumptions: minimised mesh. Shared edges won't work without shared verts.
Topology.GenerateEdges();
// How many edges do we have? exchange some percentage of them...
int numPerturbations = (int)((float)Topology.Edges.Count * ratio);
int numTriangles = mesh.vertices.Length;
List <Int64> keys = new List <Int64>(Topology.Edges.Keys);
List <int> visitedTris = new List <int>();
for (int i = 0; i < numPerturbations; ++i)
{
// Choose a random edge:
int edgeIndex = rand.Next(Topology.Edges.Count);
// Check out the tris around the edge.
Int64 key = keys[edgeIndex];
Edge edge = Topology.Edges[key];
// TODO - add flag to triangle to avoid n2/2 lookup.
bool r = false;
foreach (var visited in visitedTris)
{
if (edge.triangle1 == visited || edge.triangle2 == visited)
{
r = true;
break;
}
}
if (r)
{
continue;
}
visitedTris.Add(edge.triangle1);
visitedTris.Add(edge.triangle2);
if (IsObtuse(edge.triangle1) || IsObtuse(edge.triangle2))
{
continue;
}
uint index1 = (uint)(key & 0xffffffff);
uint index2 = (uint)((key >> 32) & 0xffffffff);
uint index3;
uint index4;
uint a = index1;
int cornerA = GetTriOffset(edge.triangle1, a);
// get the next coord in the triangle (in ccw order)
uint b = indices[edge.triangle1 * 3 + ((cornerA + 1) % 3)];
uint c = indices[edge.triangle1 * 3 + ((cornerA + 2) % 3)];
uint d = 0;
if (b == index2)
{
d = indices[edge.triangle2 * 3 + ((GetTriOffset(edge.triangle2, a) + 1) % 3)];
index3 = c;
index4 = d;
}
else
{
d = indices[edge.triangle2 * 3 + ((GetTriOffset(edge.triangle2, a) + 2) % 3)];
index3 = b;
index4 = d;
}
if (Topology.TrianglesPerVertex[index1] <= 5 || Topology.TrianglesPerVertex[index2] <= 5 ||
Topology.TrianglesPerVertex[index3] >= 7 || Topology.TrianglesPerVertex[index4] >= 7)
{
continue;
}
// Check edge lengths
Vector3 pos1 = MeshAttr.GetPosition(ref mesh.vertices[index1]);
Vector3 pos2 = MeshAttr.GetPosition(ref mesh.vertices[index2]);
Vector3 pos3 = MeshAttr.GetPosition(ref mesh.vertices[index3]);
Vector3 pos4 = MeshAttr.GetPosition(ref mesh.vertices[index4]);
float oldLength = new Vector3(pos2 - pos1).Length;
float newLength = new Vector3(pos4 - pos3).Length;
if (oldLength / newLength >= 2 || oldLength / newLength <= 0.5f)
{
continue;
}
Topology.TrianglesPerVertex[index1]--;
Topology.TrianglesPerVertex[index2]--;
Topology.TrianglesPerVertex[index3]++;
Topology.TrianglesPerVertex[index4]++;
// Need to keep tris in CCW order.
if (b == index2)
{
// order is a b c; c is the non-shared vertex.
// new tris are: ADC, DBC
// tri2 order is a d b
indices[edge.triangle1 * 3] = a;
indices[edge.triangle1 * 3 + 1] = d;
indices[edge.triangle1 * 3 + 2] = c;
indices[edge.triangle2 * 3] = d;
indices[edge.triangle2 * 3 + 1] = b;
indices[edge.triangle2 * 3 + 2] = c;
}
else
{
// order is a b c; b is the non-shared value
// new tris are ACD, CBD
// tri2 order is a b d
indices[edge.triangle1 * 3] = a;
indices[edge.triangle1 * 3 + 1] = b;
indices[edge.triangle1 * 3 + 2] = d;
indices[edge.triangle2 * 3] = c;
indices[edge.triangle2 * 3 + 1] = d;
indices[edge.triangle2 * 3 + 2] = b;
}
}
Topology.Regenerate();
}