protected int auxiliaryNextEdgeId(int prevEdgeId, int curEdgeId,
VPFPrimitiveData.PrimitiveInfo[] edgeInfoArray)
{
// Note: an edge which has the same face for both its left and right faces is known to be an "auxiliary edge".
// Using auxiliary edges is a solution to defining a face (polygon) with holes. The face becomes a single loop,
// with an auxiliary edge joining each inner and outer loop. The auxiliary edge is traversed twice; one upon
// entering the inner ring, then again upon exit.
VPFPrimitiveData.EdgeInfo prevInfo = getEdgeInfo(edgeInfoArray, prevEdgeId);
VPFPrimitiveData.EdgeInfo curInfo = getEdgeInfo(edgeInfoArray, curEdgeId);
// Previous edge is adjacent to starting node.
if (curInfo.getStartNode() == prevInfo.getStartNode() || curInfo.getStartNode() == prevInfo.getEndNode())
{
return((curInfo.getRightEdge() != curEdgeId) ? curInfo.getRightEdge() : curInfo.getLeftEdge());
}
// Previous edge is adjacent to ending node.
else if (curInfo.getEndNode() == prevInfo.getStartNode() || curInfo.getEndNode() == prevInfo.getEndNode())
{
return((curInfo.getLeftEdge() != curEdgeId) ? curInfo.getLeftEdge() : curInfo.getRightEdge());
}
// Edges are not actually adjacent. This should never happen, but we check anyway.
else
{
return(-1);
}
}
protected bool auxiliaryMustReverseCoordinates(int prevEdgeId, int curEdgeId,
VPFPrimitiveData.PrimitiveInfo[] edgeInfoArray)
{
VPFPrimitiveData.EdgeInfo prevInfo = getEdgeInfo(edgeInfoArray, prevEdgeId);
VPFPrimitiveData.EdgeInfo curInfo = getEdgeInfo(edgeInfoArray, curEdgeId);
return(curInfo.getEndNode() == prevInfo.getStartNode() || curInfo.getEndNode() == prevInfo.getEndNode());
}