static void Swap(ref MeshUtils.Vertex a, ref MeshUtils.Vertex b)
{
var tmp = a;
a = b;
b = tmp;
}
public static float TransSign(MeshUtils.Vertex u, MeshUtils.Vertex v, MeshUtils.Vertex w)
{
Debug.Assert(TransLeq(u, v) && TransLeq(v, w));
float gapL = v._t - u._t;
float gapR = w._t - v._t;
if (gapL + gapR > 0.0f)
{
return((v._s - w._s) * gapL + (v._s - u._s) * gapR);
}
/* vertical line */
return(0.0f);
}
/// <summary>
/// Returns a number whose sign matches EdgeEval(u,v,w) but which
/// is cheaper to evaluate. Returns > 0, == 0 , or less than 0
/// as v is above, on, or below the edge uw.
/// </summary>
public static float EdgeSign(MeshUtils.Vertex u, MeshUtils.Vertex v, MeshUtils.Vertex w)
{
// Debug.Assert(VertLeq(u, v) && VertLeq(v, w));
float gapL = v._s - u._s;
float gapR = w._s - v._s;
if (gapL + gapR > 0.0f)
{
return((v._t - w._t) * gapL + (v._t - u._t) * gapR);
}
/* vertical line */
return(0.0f);
}
/// <summary>
/// Given three vertices u,v,w such that VertLeq(u,v) .and. VertLeq(v,w),
/// evaluates the t-coord of the edge uw at the s-coord of the vertex v.
/// Returns v->t - (uw)(v->s), ie. the signed distance from uw to v.
/// If uw is vertical (and thus passes thru v), the result is zero.
///
/// The calculation is extremely accurate and stable, even when v
/// is very close to u or w. In particular if we set v->t = 0 and
/// let r be the negated result (this evaluates (uw)(v->s)), then
/// r is guaranteed to satisfy MIN(u->t,w->t) less than or equal r less than or equal MAX(u->t,w->t).
/// </summary>
public static float EdgeEval(MeshUtils.Vertex u, MeshUtils.Vertex v, MeshUtils.Vertex w)
{
Debug.Assert(VertLeq(u, v) && VertLeq(v, w));
float gapL = v._s - u._s;
float gapR = w._s - v._s;
if (gapL + gapR > 0.0f)
{
if (gapL < gapR)
{
return((v._t - u._t) + (u._t - w._t) * (gapL / (gapL + gapR)));
}
return((v._t - w._t) + (w._t - u._t) * (gapR / (gapL + gapR)));
}
/* vertical line */
return(0.0f);
}
public static float TransEval(MeshUtils.Vertex u, MeshUtils.Vertex v, MeshUtils.Vertex w)
{
Debug.Assert(TransLeq(u, v) && TransLeq(v, w));
float gapL = v._t - u._t;
float gapR = w._t - v._t;
if (gapL + gapR > 0.0f)
{
if (gapL < gapR)
{
return((v._s - u._s) + (u._s - w._s) * (gapL / (gapL + gapR)));
}
return((v._s - w._s) + (w._s - u._s) * (gapR / (gapL + gapR)));
}
/* vertical line */
return(0.0f);
}
// ReSharper restore InconsistentNaming
public Mesh()
{
var v = _vHead = new MeshUtils.Vertex();
var f = _fHead = new MeshUtils.Face();
var pair = MeshUtils.EdgePair.Create();
var e = _eHead = pair._e;
var eSym = _eHeadSym = pair._eSym;
v._next = v._prev = v;
v._anEdge = null;
f._next = f._prev = f;
f._anEdge = null;
f._trail = null;
f._marked = false;
f._inside = false;
e._next = e;
e._Sym = eSym;
e._Onext = null;
e._Lnext = null;
e._Org = null;
e._Lface = null;
e._winding = 0;
e._activeRegion = null;
eSym._next = eSym;
eSym._Sym = e;
eSym._Onext = null;
eSym._Lnext = null;
eSym._Org = null;
eSym._Lface = null;
eSym._winding = 0;
eSym._activeRegion = null;
}
public static bool VertLeq(MeshUtils.Vertex lhs, MeshUtils.Vertex rhs)
{
// ReSharper disable CompareOfFloatsByEqualityOperator
return((lhs._s < rhs._s) || (lhs._s == rhs._s && lhs._t <= rhs._t));
// ReSharper restore CompareOfFloatsByEqualityOperator
}
public static bool VertCcw(MeshUtils.Vertex u, MeshUtils.Vertex v, MeshUtils.Vertex w)
{
return((u._s * (v._t - w._t) + v._s * (w._t - u._t) + w._s * (u._t - v._t)) >= 0.0f);
}
/// <summary>
/// Given edges (o1,d1) and (o2,d2), compute their point of intersection.
/// The computed point is guaranteed to lie in the intersection of the
/// bounding rectangles defined by each edge.
/// </summary>
public static void EdgeIntersect(MeshUtils.Vertex o1, MeshUtils.Vertex d1, MeshUtils.Vertex o2, MeshUtils.Vertex d2, MeshUtils.Vertex v)
{
float z1, z2;
// This is certainly not the most efficient way to find the intersection
// of two line segments, but it is very numerically stable.
//
// Strategy: find the two middle vertices in the VertLeq ordering,
// and interpolate the intersection s-value from these. Then repeat
// using the TransLeq ordering to find the intersection t-value.
if (!VertLeq(o1, d1))
{
Swap(ref o1, ref d1);
}
if (!VertLeq(o2, d2))
{
Swap(ref o2, ref d2);
}
if (!VertLeq(o1, o2))
{
Swap(ref o1, ref o2); Swap(ref d1, ref d2);
}
if (!VertLeq(o2, d1))
{
// Technically, no intersection -- do our best
v._s = (o2._s + d1._s) / 2.0f;
}
else if (VertLeq(d1, d2))
{
// Interpolate between o2 and d1
z1 = EdgeEval(o1, o2, d1);
z2 = EdgeEval(o2, d1, d2);
if (z1 + z2 < 0.0f)
{
z1 = -z1;
z2 = -z2;
}
v._s = Interpolate(z1, o2._s, z2, d1._s);
}
else
{
// Interpolate between o2 and d2
z1 = EdgeSign(o1, o2, d1);
z2 = -EdgeSign(o1, d2, d1);
if (z1 + z2 < 0.0f)
{
z1 = -z1;
z2 = -z2;
}
v._s = Interpolate(z1, o2._s, z2, d2._s);
}
// Now repeat the process for t
if (!TransLeq(o1, d1))
{
Swap(ref o1, ref d1);
}
if (!TransLeq(o2, d2))
{
Swap(ref o2, ref d2);
}
if (!TransLeq(o1, o2))
{
Swap(ref o1, ref o2); Swap(ref d1, ref d2);
}
if (!TransLeq(o2, d1))
{
// Technically, no intersection -- do our best
v._t = (o2._t + d1._t) / 2.0f;
}
else if (TransLeq(d1, d2))
{
// Interpolate between o2 and d1
z1 = TransEval(o1, o2, d1);
z2 = TransEval(o2, d1, d2);
if (z1 + z2 < 0.0f)
{
z1 = -z1;
z2 = -z2;
}
v._t = Interpolate(z1, o2._t, z2, d1._t);
}
else
{
// Interpolate between o2 and d2
z1 = TransSign(o1, o2, d1);
z2 = -TransSign(o1, d2, d1);
if (z1 + z2 < 0.0f)
{
z1 = -z1;
z2 = -z2;
}
v._t = Interpolate(z1, o2._t, z2, d2._t);
}
}
public static float VertL1Dist(MeshUtils.Vertex u, MeshUtils.Vertex v)
{
return(Math.Abs(u._s - v._s) + Math.Abs(u._t - v._t));
}
