Mr. Suri wrote: 1. If a REGION object has a number of polygons within it, is it necessary that the first polygon is the outermost ring and the other polygons are inner rings ? Is it correct to assume it this way ? 2. Can 2 REGION objects share a polygon ?( i.e. Duplication of polygons ) I think I can answer these questions unequivocally: The MIF region format makes no assumptions about the order of the polygons listed in the MIF. The inside/outside relationship is calculated when the object is read. In very large objects, this may be the bulk of the time spent reading the object. A polygon is regarded as a hole if and only if it is completely inside another polygon. Polygons that overlap each other are therefore not holes of each other and a region containing such polygons, while technically supported, is not recommended. The display will probably not be correct (the colors will negate each other in the overlap area) and the mouse and selection hit-testing will be off in the overlapping area. However, the area calculation will clearly show that the polygons are not being treated as holes as the area is the sum of the parts. In a region with a hole, the area of the inner polygon is subtracted from the outer ring. I know of no problems with correctly determining the inside/outside relationship from a MIF as long as the data does not have self-intersections within a single polygon that might affect the inside/outside determination. If someone has an example of this, we would be happy to look at it and fix it if there is a problem. There is no ability to share polygons amongst multiple objects. In fact, there is no POLYGON object type in MapInfo TAB format. It is just a region with a single set of nodes. I hope this helps and Happy New Year to all! Eric Blasenheim Software Architect MapInfo Corporation _______________________________________________________________________ List hosting provided by Directions Magazine | www.directionsmag.com | To unsubscribe, send e-mail to [EMAIL PROTECTED] and put "unsubscribe MapInfo-L" in the message body.
