public PlacementNode UpdateMiddleTrapezoid(Trapezoid oldTrap, HalfEdge edge, ref Trapezoid lNeighborTop, ref Trapezoid lNeighborBottom)
{
(var belowFace, var aboveFace) = GetFaces(edge);
Trapezoid above, below;
TrapNode aboveNode, belowNode;
Debug.Assert(oldTrap.LeftTop == null ^ oldTrap.LeftBottom == null);
if (oldTrap.LeftTop == null)
{
// Left side originates above so merge bottom trapezoids
below = lNeighborBottom;
belowNode = below.Node;
below.RightVtx = oldTrap.RightVtx;
}
else
{
below = new Trapezoid
{
RightVtx = oldTrap.RightVtx,
LeftVtx = oldTrap.LeftVtx,
LeftTop = lNeighborBottom,
BottomEdge = oldTrap.BottomEdge,
TopEdge = edge,
ContainingFace = belowFace
};
belowNode = new TrapNode(below);
lNeighborBottom.RightTop = below;
}
if (oldTrap.LeftBottom == null)
{
above = lNeighborTop;
aboveNode = above.Node;
above.RightVtx = oldTrap.RightVtx;
}
else
{
above = new Trapezoid
{
RightVtx = oldTrap.RightVtx,
LeftVtx = oldTrap.LeftVtx,
BottomEdge = edge,
TopEdge = oldTrap.TopEdge,
ContainingFace = aboveFace
};
aboveNode = new TrapNode(above);
lNeighborTop.RightBottom = above;
}
lNeighborTop = above;
lNeighborBottom = below;
return(new YNode(edge.InitVertex.Position, edge.NextVertex.Position, aboveNode, belowNode));
}
////////////////////////////////////////////////////////////////////////////////////////////////////
/// <summary> Updates the Trapezoid which an endpoint of the edge is located in. </summary>
///
/// <remarks> Note - we presume the caller is modifying trapezoids intersected by the side from
/// left to right. The lNeighborTop and lNeighborBottom are the top and bottom
/// trapezoids created by the edge splitting in the trapezoid to our left. This is
/// so we can merge one of our upper or lower traps with the one on the left. Generally
/// we can't merge right traps into left ones because the right trapezoids haven't been
/// created yet.
///
/// Darrell Plank, 2/12/2018. </remarks>
///
/// <param name="oldTrap"> The trapNode which contains the left endpoint. </param>
/// <param name="edge"> The edge whose left endpoint is in the trapezoid. </param>
/// <param name="lNeighborTop"> The left neighbor's top trapezoid </param>
/// <param name="lNeighborBottom"> The left neighbor's bottom trapezoid </param>
////////////////////////////////////////////////////////////////////////////////////////////////////
public PlacementNode UpdateEndTrapezoid(Trapezoid oldTrap, HalfEdge edge, ref Trapezoid lNeighborTop, ref Trapezoid lNeighborBottom)
{
(var belowFace, var aboveFace) = GetFaces(edge);
// The edge splits some portion of our trapezoid vertically. Determine the extent of that
// region and which vertices bound it.
var trapLeft = oldTrap.LeftVtx.X;
var trapRight = oldTrap.RightVtx.X;
var edgeLeft = edge.InitVertex.X;
var edgeRight = edge.NextVertex.X;
// "meets" in this context means the side shares a previously established vertex.
// "exceeds" means "goes past" which means it splits through
// the side of the trap. If neither of these is true, it ends in the proper
// interior of the trapezoid.
// We can use equality here since these will be coming from a shared vertex
// ReSharper disable CompareOfFloatsByEqualityOperator
var meetsLeft = trapLeft == edgeLeft;
var meetsRight = trapRight == edgeRight;
// ReSharper restore CompareOfFloatsByEqualityOperator
//
var exceedsLeft = trapLeft > edgeLeft;
var exceedsRight = trapRight < edgeRight;
var interiorLeft = trapLeft < edgeLeft;
var interiorRight = trapRight > edgeRight;
var midRightVtx = meetsRight || exceedsRight ? oldTrap.RightVtx : edge.NextVertex;
var midLeftVtx = meetsLeft || exceedsLeft ? oldTrap.LeftVtx : edge.InitVertex;
// The newly created traps to be inserted into the map
Trapezoid above, below, left, right;
// Create left trapezoid if necessary
if (interiorLeft)
{
left = new Trapezoid
{
RightVtx = midLeftVtx,
LeftVtx = oldTrap.LeftVtx,
LeftTop = oldTrap.LeftTop,
LeftBottom = oldTrap.LeftBottom,
BottomEdge = oldTrap.BottomEdge,
TopEdge = oldTrap.TopEdge,
ContainingFace = oldTrap.ContainingFace
};
oldTrap.LeftBottom?.LinkTo(oldTrap, left, true);
oldTrap.LeftTop?.LinkTo(oldTrap, left, true);
}
else
{
left = null;
}
// Create right trapezoid if necessary
if (interiorRight)
{
right = new Trapezoid
{
RightVtx = oldTrap.RightVtx,
LeftVtx = midRightVtx,
RightBottom = oldTrap.RightBottom,
LeftBottom = oldTrap.LeftBottom,
BottomEdge = oldTrap.BottomEdge,
TopEdge = oldTrap.TopEdge,
ContainingFace = oldTrap.ContainingFace
};
oldTrap.RightBottom?.LinkTo(oldTrap, right, false);
oldTrap.RightTop?.LinkTo(oldTrap, right, false);
}
else
{
right = null;
}
TrapNode aboveNode = null, belowNode = null;
// Create top/bottom trapezoids (which is always necessary)
if (exceedsLeft)
{
// These assumptions need to be met when merging below. This should all compile out
// in the release build.
Debug.Assert(oldTrap.LeftTop == null ^ oldTrap.LeftBottom == null);
Debug.Assert(lNeighborBottom != null && lNeighborTop != null);
if (oldTrap.LeftBottom == null)
{
// Old trap's left side comes up from vertex below and we're cutting it off so merge top traps
above = lNeighborTop;
above.RightVtx = midRightVtx;
aboveNode = above.Node;
// Create new bottom trap
below = new Trapezoid
{
RightVtx = midRightVtx,
LeftVtx = midLeftVtx,
LeftTop = lNeighborBottom,
TopEdge = edge,
BottomEdge = oldTrap.BottomEdge,
ContainingFace = belowFace
};
lNeighborBottom.RightTop = below;
}
else
{
// Merge bottom traps
below = lNeighborBottom;
below.RightVtx = midRightVtx;
belowNode = below.Node;
// Create new top trap
above = new Trapezoid
{
RightVtx = midRightVtx,
LeftVtx = midLeftVtx,
LeftBottom = lNeighborTop,
BottomEdge = edge,
TopEdge = oldTrap.TopEdge,
ContainingFace = aboveFace
};
lNeighborTop.RightBottom = above;
}
}
else if (meetsLeft)
{
var leftOfTopTrap = oldTrap.LeftTop;
var leftOfBottomTrap = oldTrap.LeftBottom;
above = new Trapezoid
{
RightVtx = midRightVtx,
LeftVtx = midLeftVtx,
LeftTop = leftOfTopTrap,
TopEdge = oldTrap.TopEdge,
BottomEdge = edge,
ContainingFace = aboveFace
};
below = new Trapezoid
{
RightVtx = midRightVtx,
LeftVtx = midLeftVtx,
LeftBottom = leftOfBottomTrap,
BottomEdge = oldTrap.BottomEdge,
TopEdge = edge,
ContainingFace = belowFace
};
oldTrap.LeftTop?.LinkTo(oldTrap, above, true);
oldTrap.LeftBottom?.LinkTo(oldTrap, below, true);
}
else
{
// Interior on left - i.e., we created a left trapezoid within the old trapezoid
above = new Trapezoid
{
RightVtx = midRightVtx,
LeftVtx = midLeftVtx,
LeftTop = left,
TopEdge = oldTrap.TopEdge,
BottomEdge = edge,
ContainingFace = aboveFace
};
below = new Trapezoid
{
RightVtx = midRightVtx,
LeftVtx = midLeftVtx,
LeftBottom = left,
BottomEdge = oldTrap.BottomEdge,
TopEdge = edge,
ContainingFace = belowFace
};
// ReSharper disable once PossibleNullReferenceException
left.RightTop = above;
left.RightBottom = below;
}
if (meetsRight)
{
above.RightTop = oldTrap.RightTop;
above.RightBottom = null;
below.RightTop = null;
below.RightBottom = oldTrap.RightBottom;
oldTrap.RightTop?.LinkTo(oldTrap, above, false);
oldTrap.RightBottom?.LinkTo(oldTrap, below, false);
}
else if (interiorRight)
{
above.RightTop = right;
above.RightBottom = null;
below.RightTop = null;
below.RightBottom = right;
right.LeftTop = above;
right.LeftBottom = below;
}
// If exceedRight then we'll be backpatched in the next trap to the right.
if (aboveNode == null)
{
aboveNode = new TrapNode(above);
}
if (belowNode == null)
{
belowNode = new TrapNode(below);
}
lNeighborTop = above;
lNeighborBottom = below;
// Okay - finally done with the map. Now to deal with the tree.
// We always have the edge split to concern ourselves with
PlacementNode repl = new YNode(edge.InitVertex.Position, edge.NextVertex.Position, aboveNode, belowNode);
// Do we split off a right trap?
if (interiorRight)
{
repl = new XNode(repl, new TrapNode(right), right.LeftVtx);
//repl = new XNode(repl, new TrapNode(right), midRight);
}
// How about splitting off a left trap?
if (interiorLeft)
{
repl = new XNode(new TrapNode(left), repl, left.RightVtx);
//repl = new XNode(new TrapNode(left), repl, midLeft);
}
return(repl);
}
