InitializeMetadata
(
IGraph oGraph,
ICollection <IVertex> oVerticesToLayOut
)
{
Debug.Assert(oGraph != null);
Debug.Assert(oVerticesToLayOut != null);
AssertValid();
foreach (IVertex oVertex in oVerticesToLayOut)
{
// Create an object that will store all calculated values for the
// vertex.
FruchtermanReingoldVertexInfo oFruchtermanReingoldVertexInfo =
new FruchtermanReingoldVertexInfo(oVertex.Location);
// The object could be stored in a metadata key, but because the
// number of retrievals can be very large, it's more efficient to
// store it in the Tag. If a Tag already exists, save it in a
// metadata key.
SaveTag(oVertex);
oVertex.Tag = oFruchtermanReingoldVertexInfo;
}
foreach (IEdge oEdge in oGraph.Edges)
{
// Do the same for edges. In this case, each edge has just one
// piece of information, the edge weight.
SaveTag(oEdge);
oEdge.Tag = (Single)EdgeUtil.GetPositiveEdgeWeight(oEdge);
}
}
InitializeMetadata
(
IGraph oGraph,
ICollection<IVertex> oVerticesToLayOut
)
{
Debug.Assert(oGraph != null);
Debug.Assert(oVerticesToLayOut != null);
AssertValid();
foreach (IVertex oVertex in oVerticesToLayOut)
{
// Create an object that will store all calculated values for the
// vertex.
FruchtermanReingoldVertexInfo oFruchtermanReingoldVertexInfo =
new FruchtermanReingoldVertexInfo(oVertex.Location);
// The object could be stored in a metadata key, but because the
// number of retrievals can be very large, it's more efficient to
// store it in the Tag. If a Tag already exists, save it in a
// metadata key.
SaveTag(oVertex);
oVertex.Tag = oFruchtermanReingoldVertexInfo;
}
foreach (IEdge oEdge in oGraph.Edges)
{
// Do the same for edges. In this case, each edge has just one
// piece of information, the edge weight.
SaveTag(oEdge);
oEdge.Tag = (Single)EdgeUtil.GetPositiveEdgeWeight(oEdge);
}
}
SetUnboundedLocations
(
ICollection <IVertex> verticesToLayOut,
LayoutContext layoutContext,
Single fTemperature,
Boolean bAlsoSetVertexLocations
)
{
Debug.Assert(verticesToLayOut != null);
Debug.Assert(layoutContext != null);
Debug.Assert(fTemperature > 0);
AssertValid();
// The following variables define the unbounded rectangle.
TMathType tMinLocationX = Single.MaxValue;
TMathType tMaxLocationX = Single.MinValue;
TMathType tMinLocationY = Single.MaxValue;
TMathType tMaxLocationY = Single.MinValue;
foreach (IVertex oVertex in verticesToLayOut)
{
// Retrieve the object that stores calculated values for the
// vertex. We need the vertex's current unbounded location and
// the displacement created by the repulsive and attractive forces
// on the vertex.
FruchtermanReingoldVertexInfo oVertexInfo =
(FruchtermanReingoldVertexInfo)oVertex.Tag;
TMathType tUnboundedLocationX =
(TMathType)oVertexInfo.UnboundedLocationX;
TMathType tUnboundedLocationY =
(TMathType)oVertexInfo.UnboundedLocationY;
TMathType tDisplacementX = (TMathType)oVertexInfo.DisplacementX;
TMathType tDisplacementY = (TMathType)oVertexInfo.DisplacementY;
TMathType tDisplacement = (TMathType)Math.Sqrt(
(tDisplacementX * tDisplacementX) +
(tDisplacementY * tDisplacementY)
);
if (tDisplacement != 0)
{
// Calculate a new unbounded location, limited by the current
// temperature.
tUnboundedLocationX += (tDisplacementX / tDisplacement) *
Math.Min(tDisplacement, (TMathType)fTemperature);
tUnboundedLocationY += (tDisplacementY / tDisplacement) *
Math.Min(tDisplacement, (TMathType)fTemperature);
}
// Update the vertex's unbounded location.
oVertexInfo.UnboundedLocationX = (Single)tUnboundedLocationX;
oVertexInfo.UnboundedLocationY = (Single)tUnboundedLocationY;
// Expand the unbounded rectangle if necessary.
tMinLocationX = Math.Min(tUnboundedLocationX, tMinLocationX);
tMaxLocationX = Math.Max(tUnboundedLocationX, tMaxLocationX);
tMinLocationY = Math.Min(tUnboundedLocationY, tMinLocationY);
tMaxLocationY = Math.Max(tUnboundedLocationY, tMaxLocationY);
}
if (!bAlsoSetVertexLocations)
{
return;
}
Debug.Assert(verticesToLayOut.Count != 0);
Debug.Assert(tMinLocationX != Single.MaxValue);
Debug.Assert(tMaxLocationX != Single.MinValue);
Debug.Assert(tMinLocationY != Single.MaxValue);
Debug.Assert(tMaxLocationY != Single.MinValue);
// Get a Matrix that will transform vertex locations from coordinates
// in the unbounded rectangle to cooordinates in the bounded graph
// rectangle.
Matrix oTransformationMatrix = LayoutUtil.GetRectangleTransformation(
RectangleF.FromLTRB(
(Single)tMinLocationX,
(Single)tMinLocationY,
(Single)tMaxLocationX,
(Single)tMaxLocationY
),
layoutContext.GraphRectangle
);
// Transform the vertex locations.
foreach (IVertex oVertex in verticesToLayOut)
{
FruchtermanReingoldVertexInfo oVertexInfo =
(FruchtermanReingoldVertexInfo)oVertex.Tag;
PointF [] aoLocation = new PointF [] {
new PointF(
oVertexInfo.UnboundedLocationX,
oVertexInfo.UnboundedLocationY
)
};
oTransformationMatrix.TransformPoints(aoLocation);
if (!VertexIsLocked(oVertex))
{
oVertex.Location = aoLocation[0];
}
}
}
CalculateAttractiveForces
(
ICollection <IEdge> edgesToLayOut,
Single k
)
{
Debug.Assert(edgesToLayOut != null);
Debug.Assert(k != 0);
AssertValid();
const String MethodName = "CalculateAttractiveForces";
foreach (IEdge oEdge in edgesToLayOut)
{
if (oEdge.IsSelfLoop)
{
// A vertex isn't attracted to itself.
continue;
}
// Get the edge's vertices.
IVertex oVertexV, oVertexU;
EdgeUtil.EdgeToVertices(oEdge, this.ClassName, MethodName,
out oVertexV, out oVertexU);
// Retrieve the objects that store calculated values for the
// vertices.
FruchtermanReingoldVertexInfo oVertexInfoV =
(FruchtermanReingoldVertexInfo)oVertexV.Tag;
FruchtermanReingoldVertexInfo oVertexInfoU =
(FruchtermanReingoldVertexInfo)oVertexU.Tag;
TMathType tDeltaX =
(TMathType)oVertexInfoV.UnboundedLocationX -
(TMathType)oVertexInfoU.UnboundedLocationX;
TMathType tDeltaY =
(TMathType)oVertexInfoV.UnboundedLocationY -
(TMathType)oVertexInfoU.UnboundedLocationY;
TMathType tDelta = (TMathType)Math.Sqrt(
(tDeltaX * tDeltaX) + (tDeltaY * tDeltaY)
);
// Use the edge weight, which InitializeMetadata() stored in the
// Tag.
tDelta *= (Single)oEdge.Tag;
TMathType tDisplacementV_X = (TMathType)oVertexInfoV.DisplacementX;
TMathType tDisplacementV_Y = (TMathType)oVertexInfoV.DisplacementY;
TMathType tDisplacementU_X = (TMathType)oVertexInfoU.DisplacementX;
TMathType tDisplacementU_Y = (TMathType)oVertexInfoU.DisplacementY;
// (Note that there is an obvious typo in the Fruchterman-Reingold
// paper for computing the attractive force. The function fa(z) at
// the top of Figure 1 is defined as x squared over k. It should
// read z squared over k.)
TMathType fa = (tDelta * tDelta) / (TMathType)k;
if (tDelta == 0)
{
// TODO: Is this the correct way to handle vertices in the same
// location? See the notes in CalculateRepulsiveForces().
continue;
}
Debug.Assert(tDelta != 0);
TMathType faOverDelta = fa / tDelta;
TMathType tFactorX = tDeltaX * faOverDelta;
TMathType tFactorY = tDeltaY * faOverDelta;
tDisplacementV_X -= tFactorX;
tDisplacementV_Y -= tFactorY;
tDisplacementU_X += tFactorX;
tDisplacementU_Y += tFactorY;
oVertexInfoV.DisplacementX = (Single)tDisplacementV_X;
oVertexInfoV.DisplacementY = (Single)tDisplacementV_Y;
oVertexInfoU.DisplacementX = (Single)tDisplacementU_X;
oVertexInfoU.DisplacementY = (Single)tDisplacementU_Y;
}
}
CalculateRepulsiveForces
(
ICollection <IVertex> verticesToLayOut,
Single k
)
{
Debug.Assert(verticesToLayOut != null);
AssertValid();
TMathType tkSquared = (TMathType)(k * k);
foreach (IVertex oVertexV in verticesToLayOut)
{
// Retrieve the object that stores calculated values for the
// vertex.
FruchtermanReingoldVertexInfo oVertexInfoV =
(FruchtermanReingoldVertexInfo)oVertexV.Tag;
TMathType tDisplacementX = 0;
TMathType tDisplacementY = 0;
foreach (IVertex oVertexU in verticesToLayOut)
{
if (oVertexU == oVertexV)
{
continue;
}
FruchtermanReingoldVertexInfo oVertexInfoU =
(FruchtermanReingoldVertexInfo)oVertexU.Tag;
TMathType tDeltaX =
(TMathType)oVertexInfoV.UnboundedLocationX -
(TMathType)oVertexInfoU.UnboundedLocationX;
TMathType tDeltaY =
(TMathType)oVertexInfoV.UnboundedLocationY -
(TMathType)oVertexInfoU.UnboundedLocationY;
TMathType tDelta = (TMathType)Math.Sqrt(
(tDeltaX * tDeltaX) + (tDeltaY * tDeltaY)
);
// The Fruchterman-Reingold paper says this about vertices in
// the same location:
//
// "A special case occurs when vertices are in the same
// position: our implementation acts as though the two vertices
// are a small distance apart in a randomly chosen orientation:
// this leads to a violent repulsive effect separating them."
//
// Handle this case by arbitrarily setting a small
// displacement.
if (tDelta == 0)
{
tDisplacementX += 1;
tDisplacementY += 1;
}
else
{
Debug.Assert(tDelta != 0);
TMathType fr = tkSquared / tDelta;
TMathType frOverDelta = fr / tDelta;
tDisplacementX += tDeltaX * frOverDelta;
tDisplacementY += tDeltaY * frOverDelta;
}
}
// Save the results for VertexV.
oVertexInfoV.DisplacementX = tDisplacementX;
oVertexInfoV.DisplacementY = tDisplacementY;
}
}
SetUp()
{
m_oFruchtermanReingoldVertexInfo = new FruchtermanReingoldVertexInfo(
new PointF(InitialLocationX, InitialLocationY) );
}
