//box2D rev 32 - for details, see http://www.box2d.org/forum/viewtopic.php?f=4&t=83&start=50
/// <summary>
/// Decompose the polygon into several smaller non-concave polygon.
/// Each resulting polygon will have no more than Settings.MaxPolygonVertices vertices.
/// </summary>
/// <param name="vertices">The vertices.</param>
/// <param name="tolerance">The tolerance.</param>
// TS - public static List<Vertices> ConvexPartition(Vertices vertices, FP tolerance = 0.001f)
public static List <Vertices> ConvexPartition(Vertices vertices, FP tolerance)
{
Debug.Assert(vertices.Count > 3);
Debug.Assert(!vertices.IsCounterClockWise());
return(TriangulatePolygon(vertices, tolerance));
}
/// <summary>
/// Decompose the polygon into several smaller non-concave polygon.
/// If the polygon is already convex, it will return the original polygon, unless it is over Settings.MaxPolygonVertices.
/// </summary>
public static List <Vertices> ConvexPartition(Vertices vertices)
{
vertices.ForceCounterClockWise();
Debug.Assert(vertices.Count > 3);
Debug.Assert(vertices.IsCounterClockWise());
return(TriangulatePolygon(vertices));
}
// TS - public static List<Vertices> ConvexPartition(Vertices vertices, TriangulationAlgorithm algorithm, bool discardAndFixInvalid = true, FP tolerance = 0.001f)
public static List<Vertices> ConvexPartition(Vertices vertices, TriangulationAlgorithm algorithm, bool discardAndFixInvalid, FP tolerance)
{
if (vertices.Count <= 3)
return new List<Vertices> { vertices };
List<Vertices> results;
switch (algorithm)
{
case TriangulationAlgorithm.Earclip:
if (Settings.SkipSanityChecks)
Debug.Assert(!vertices.IsCounterClockWise(), "The Earclip algorithm expects the polygon to be clockwise.");
else
{
if (vertices.IsCounterClockWise())
{
Vertices temp = new Vertices(vertices);
temp.Reverse();
results = EarclipDecomposer.ConvexPartition(temp, tolerance);
}
else
results = EarclipDecomposer.ConvexPartition(vertices, tolerance);
}
break;
case TriangulationAlgorithm.Bayazit:
if (Settings.SkipSanityChecks)
Debug.Assert(vertices.IsCounterClockWise(), "The polygon is not counter clockwise. This is needed for Bayazit to work correctly.");
else
{
if (!vertices.IsCounterClockWise())
{
Vertices temp = new Vertices(vertices);
temp.Reverse();
results = BayazitDecomposer.ConvexPartition(temp);
}
else
results = BayazitDecomposer.ConvexPartition(vertices);
}
break;
case TriangulationAlgorithm.Flipcode:
if (Settings.SkipSanityChecks)
Debug.Assert(vertices.IsCounterClockWise(), "The polygon is not counter clockwise. This is needed for Bayazit to work correctly.");
else
{
if (!vertices.IsCounterClockWise())
{
Vertices temp = new Vertices(vertices);
temp.Reverse();
results = FlipcodeDecomposer.ConvexPartition(temp);
}
else
results = FlipcodeDecomposer.ConvexPartition(vertices);
}
break;
case TriangulationAlgorithm.Seidel:
results = SeidelDecomposer.ConvexPartition(vertices, tolerance);
break;
case TriangulationAlgorithm.SeidelTrapezoids:
results = SeidelDecomposer.ConvexPartitionTrapezoid(vertices, tolerance);
break;
case TriangulationAlgorithm.Delauny:
results = CDTDecomposer.ConvexPartition(vertices);
break;
default:
throw new ArgumentOutOfRangeException("algorithm");
}
if (discardAndFixInvalid)
{
for (int i = results.Count - 1; i >= 0; i--)
{
Vertices polygon = results[i];
if (!ValidatePolygon(polygon))
results.RemoveAt(i);
}
}
return results;
}
/// <summary>
/// Decompose the polygon into triangles.
///
/// Properties:
/// - Only works on counter clockwise polygons
///
/// </summary>
/// <param name="vertices">The list of points describing the polygon</param>
public static List <Vertices> ConvexPartition(Vertices vertices)
{
Debug.Assert(vertices.Count > 3);
Debug.Assert(vertices.IsCounterClockWise());
int[] polygon = new int[vertices.Count];
for (int v = 0; v < vertices.Count; v++)
{
polygon[v] = v;
}
int nv = vertices.Count;
// Remove nv-2 Vertices, creating 1 triangle every time
int count = 2 * nv; /* error detection */
List <Vertices> result = new List <Vertices>();
for (int v = nv - 1; nv > 2;)
{
// If we loop, it is probably a non-simple polygon
if (0 >= (count--))
{
// Triangulate: ERROR - probable bad polygon!
return(new List <Vertices>());
}
// Three consecutive vertices in current polygon, <u,v,w>
int u = v;
if (nv <= u)
{
u = 0; // Previous
}
v = u + 1;
if (nv <= v)
{
v = 0; // New v
}
int w = v + 1;
if (nv <= w)
{
w = 0; // Next
}
_tmpA = vertices[polygon[u]];
_tmpB = vertices[polygon[v]];
_tmpC = vertices[polygon[w]];
if (Snip(vertices, u, v, w, nv, polygon))
{
int s, t;
// Output Triangle
Vertices triangle = new Vertices(3);
triangle.Add(_tmpA);
triangle.Add(_tmpB);
triangle.Add(_tmpC);
result.Add(triangle);
// Remove v from remaining polygon
for (s = v, t = v + 1; t < nv; s++, t++)
{
polygon[s] = polygon[t];
}
nv--;
// Reset error detection counter
count = 2 * nv;
}
}
return(result);
}
