The first thing you have to do, is analyze what is currently there in FSX. For example, let's assume it is a lake or ocean area, currently shown as water in FSX, and you now want to place an island in that water.
There are a couple of possible approaches, but I think the main options would be to 1. remove the existing water area, and replace it with water that includes the island, or 2. place an island by drawing land area on top of the existing water.
There are a couple of considerations:
method 1 has the advantage, that it will allow any elevation mesh that exists for the island to be shown. Of course, if there isn't any mesh, or your island is fictional that isn't any benefit. The disadvantage, is that you have to re-create the existing water body in its entirety (the typical water body is a polygon that is contained within a QMID 11 boundary -- these boundaries are shown by turning on the QMID display in SBX). In the unlucky event that your island crosses into 2 or more different QMID 11 cells, this can result in quite a bit of rework.
method 2 has the advantage of leaving the existing water body intact, but at the expense of having to recreate the elevation mesh of the island (if you want your island to be flat, that isn't a big problem of course).
To do method 1, first you need to be able to recreate any coastline that your water body must provide (including your new island). this can be done by using a satellite image as a background and tracing a coastline, or loading the default (or other terrain file that supplies the water body) in the sdk tmfviewer program, taking a screenshot that covers the water body, and using that as a map in SBX (You can set a QMID 11 grid in tmfviewer as well, and use that to calibrate the map). Once you have your background or map, you can create a rectangle area within the water body (doesn't need to be exact) set to exclude hydro polygons. That will get rid of the water body. Now you create new polygons tracing the coastline in the background or map. Where the new water body is bounded by one of the QMID 11 grid boundaries, I just extend the polygon out to the neighboring cell, and then use the "clip" function to slice the polygon accurately at the border.
Once you have created the water body, the use the same technique to create the island. When you finish the island, select it and use the context menu option to set as hole, then click on the water polygon to set it as the parent of the hole. (A hole must be completely within its parent and can only have 1 parent).
To do method 2, just trace out the coastline of your island as a polygon, this time set to Legacy_LWM_Land_Flatten. You must also set your altitude elevation or it will be at the same elevation as the water body.
With either method, at this point there will probably be no visible land, since there probably isn't any landclass defined for the area of your island. You can either use the landclass function in SBX to place appropriate landclass textures on your island (make sure the number of landclass tiles you define extend out from your island a bit or you might not get 100% coverage in the sim due to how FS blends landclass textures together), or you can create a copy of your island poly and place right on top of your original one, but set it to a specific landclass texture.
If you want a shoreline, possibly with breaking surf, you must select the poly for your island, or other coast, and use the "make line" function to create a matching line, which you set to an appropriate shoreline. Depending on your poly configuration, you might be missing a segment of the coastline (where the line starts and ends) which you can draw by hand, and you might need to reverse the direction of the line if your beach/surf is on the wrong side.
When working with shorelines and matching island coasts, it can be helpful to use the "view" menu to turn polygons or lines on/off to declutter your view. Be mindful of what tool you have active: selection/pointer, line, or poly as your results of any operation might depend on which tool you have active.
scott s.
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