/**
* Assumes that the polygons are disjoint. Find the vertex indices corresponding to the end points
* of the two connecting edges.
*
* @param polygon1 the first polygon
* @param polygon2 the second polygon
* @param verticesIndices in[2][2] contains the indexes of the connecting edges end points. The
* row index refers to which polygon the vertex index belongs to, whereas the column index
* refers to which connecting edge the vertex index belongs to. For example,
* vertexIndexes[0][1] is the index of the vertex of the first polygon, also end point the
* second connecting edge.
* @return success (false = failed, true = succeeded)
*/
public static boolean findConnectingEdgesVerticesIndexes(
ConvexPolygon2d polygon1, ConvexPolygon2d polygon2, int[][] verticesIndices) {
boolean success = false;
if (polygon1.isEmpty() || polygon2.isEmpty()) return false;
if (polygon1.hasExactlyOneVertex() && polygon2.hasExactlyOneVertex()) {
verticesIndices[0][0] = 0;
verticesIndices[0][1] = 0;
verticesIndices[1][0] = 0;
verticesIndices[1][1] = 0;
return true;
}
if (polygon1.hasExactlyOneVertex()) {
verticesIndices[0][0] = 0;
verticesIndices[0][1] = 0;
success = polygon2.getLineOfSightVerticesIndices(polygon1.getVertex(0), verticesIndices[1]);
return success;
}
if (polygon2.hasExactlyOneVertex()) {
verticesIndices[1][0] = 0;
verticesIndices[1][1] = 0;
success = polygon1.getLineOfSightVerticesIndices(polygon2.getVertex(0), verticesIndices[0]);
return success;
}
// First pick a random vertex from polygon1
Point2d vertex = polygon1.getVertex(0);
int[] lineOfSight1 = new int[2];
int[] lineOfSight2 = new int[2];
int L1, R1, L2, R2;
// Then find its two line of sight points on polygon 2:
success = polygon2.getLineOfSightVerticesIndices(vertex, lineOfSight1);
if (!success) return false;
L2 = lineOfSight1[0];
R2 = lineOfSight1[1];
// Then find the line of sight vertices on polygon 1:
success = polygon1.getLineOfSightVerticesIndices(polygon2.getVertex(R2), lineOfSight1);
if (!success) return false;
success = polygon1.getLineOfSightVerticesIndices(polygon2.getVertex(L2), lineOfSight2);
if (!success) return false;
L1 = lineOfSight1[0];
R1 = lineOfSight2[1];
// Find the line of sight vertices back and forth between the two polygons until they are
// constant between two iterations.
boolean done = false;
while (!done) {
success = polygon2.getLineOfSightVerticesIndices(polygon1.getVertex(L1), lineOfSight1);
if (!success) return false;
success = polygon2.getLineOfSightVerticesIndices(polygon1.getVertex(R1), lineOfSight2);
if (!success) return false;
if ((L2 == lineOfSight2[0]) && (R2 == lineOfSight1[1])) {
done = true;
break;
}
L2 = lineOfSight2[0];
R2 = lineOfSight1[1];
success = polygon1.getLineOfSightVerticesIndices(polygon2.getVertex(L2), lineOfSight1);
if (!success) return false;
success = polygon1.getLineOfSightVerticesIndices(polygon2.getVertex(R2), lineOfSight2);
if (!success) return false;
if ((L1 == lineOfSight2[0]) && (R1 == lineOfSight1[1])) {
done = true;
break;
}
L1 = lineOfSight2[0];
R1 = lineOfSight1[1];
}
verticesIndices[0][0] = R1;
verticesIndices[0][1] = L1;
verticesIndices[1][0] = L2;
verticesIndices[1][1] = R2;
return true;
}
