doesBoundaryIntersectPolygon static method

bool doesBoundaryIntersectPolygon(BoundingBox boundary, List<ILatLong> polygon)

Checks if a bounding box (boundary) intersects with a polygon.

This method determines if a polygon would be visible within the given boundary by checking for various types of intersections:

• Boundary completely inside polygon
• Polygon completely inside boundary
• Partial intersection (polygon edges cross boundary edges)

boundary The rectangular boundary to test against polygon List of vertices defining the polygon Returns true if the polygon intersects with or is contained within the boundary

Implementation

static bool doesBoundaryIntersectPolygon(BoundingBox boundary, List<ILatLong> polygon) {
  if (polygon.length < 3) return false;

  // Get boundary corner points
  List<ILatLong> boundaryCorners = [
    LatLong(boundary.maxLatitude, boundary.minLongitude), // top-left
    LatLong(boundary.maxLatitude, boundary.maxLongitude), // top-right
    LatLong(boundary.minLatitude, boundary.maxLongitude), // bottom-right
    LatLong(boundary.minLatitude, boundary.minLongitude), // bottom-left
  ];

  // Check if boundary is completely inside polygon
  // If all boundary corners are inside the polygon, boundary is contained
  bool allCornersInside = true;
  for (ILatLong corner in boundaryCorners) {
    if (!isPointInPolygon(corner, polygon)) {
      allCornersInside = false;
      break;
    }
  }
  if (allCornersInside) return true;

  // Check if polygon is completely inside boundary
  // If all polygon vertices are inside the boundary, polygon is contained
  bool allVerticesInside = true;
  for (ILatLong vertex in polygon) {
    if (!boundary.containsLatLong(vertex)) {
      allVerticesInside = false;
      break;
    }
  }
  if (allVerticesInside) return true;

  // Check for edge intersections between polygon and boundary
  // Get boundary edges
  List<List<ILatLong>> boundaryEdges = [
    [boundaryCorners[0], boundaryCorners[1]], // top edge
    [boundaryCorners[1], boundaryCorners[2]], // right edge
    [boundaryCorners[2], boundaryCorners[3]], // bottom edge
    [boundaryCorners[3], boundaryCorners[0]], // left edge
  ];

  // Check each polygon edge against each boundary edge
  for (int i = 0; i < polygon.length; i++) {
    ILatLong polygonStart = polygon[i];
    ILatLong polygonEnd = polygon[(i + 1) % polygon.length];

    for (List<ILatLong> boundaryEdge in boundaryEdges) {
      if (doLinesIntersect(polygonStart, polygonEnd, boundaryEdge[0], boundaryEdge[1])) {
        return true;
      }
    }
  }

  // Check if any polygon vertex is inside the boundary (partial containment)
  for (ILatLong vertex in polygon) {
    if (boundary.containsLatLong(vertex)) {
      return true;
    }
  }

  // Check if any boundary corner is inside the polygon (partial containment)
  for (ILatLong corner in boundaryCorners) {
    if (isPointInPolygon(corner, polygon)) {
      return true;
    }
  }

  return false;
}