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bob.bernstein

How many Photoreal tiles per bgl?

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The area I'm working on is aproaching 20x20 photoreal tiles and getting bigger. It seems to take forever for all the mip maps to load. I know it's OK to overlap but how much should I break it up?appologies for the double post. My internet connection isn't working well today.

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Howdy:others will hopefully correct me if I'm wrong but I don't think the extent matters much unless it's a truly huge file. The reason is that FS will load all textures within the active area, default and/or custom, when initiating a flight. I don't know the actual extent of it but I have an 8500 tile project (which is actually split into 4 parts) that will load completely if I start a flight somewhere inside it. You can check this by going into top-down view and zooming out to see where the unsharp areas begin. On the other hand, it is possible that, when moving into a photoreal area from the outside, loading times might be quicker if the scenery file references a smaller area. It would be interesting to know if anyone has ever tested this. There is a utility out there that allows one to track file access; maybe that can provide some insights. It's available here: http://www.sysinternals.com/ntw2k/source/filemon.shtmlCheers, Holger

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8500 Tiles!! Wow! That must take up over 350 meg! How many square miles/kilometers does that cover? If I remember right you are working on the AK/BC area. Does each tile cover a smaller area that far north? Each of my tiles covers about .78 square miles and I now have a 17x23 tile area covered or about 305 square miles. If you set visibility at 70 miles than you could conceivably see almost 2000 square miles so you are right, it would load all of them.But I still wonder if deviding the area into smaller, overlapping bgls wouldn't cause them to load in a more orderly manner (ie the ones in front of you or that you're looking at first). Especially as you enter the area from an edge.Regards,John

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There is a seperate factor to consider here, which may help make up your decision on "how many tiles" per bgl. Depending on your source for photography and your skill at reprojecting that photography to wgs84 geographic projection, you may find it helpful to consider each airport your scenery contains as the center of a bgl, because the airports represent a unique spot that has a clear location pinned down in both the fs world and your image. I tend to use two point calibration for my photos so that the image resides correctly over each runway, and then work the overlap of imagry so that a correct blend occurs. This is because my efforts at reprojecting large areas have proven unsatisfying. Using simple rotations, one can get an airport to line up pretty well, but a second airport 10 miles away will likely not line up well.Solving my "line up" problems my way has the unintended side effect of capturing only a limited number of images in any given bgl.Bob Bernstein

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That would preclude you from overlapping the two area since each tile location on earth has one unique name and you would have to choose a tile from one or the other area. It would also seem that there would be a line where nothing matched up unless you left some default scenery between.John

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well sure...this is an issue that must be managed...but the alternative is entire airports that don't fit their image....or....artifically feathering the airport image into a place it isn't really in...or....leave some default between the areas....or master the reprojection of the entire area.I think that's the entirety of the choices.What I did with the overlap is to perform resample once for each area. Now you'll have two images with the same name, as you point out. Imagine the areas sharing an e/w border. Each area will have a different version of each overlap lod13 grid. Thus 2 different textures, each correct at their respective edge...the eastern most area will have the eastern most edge of the overlap texture that you'd want to maintain. Likewise the western most edge of the western most area's version of that texture. Using layers in a good editing software, its not all that hard to create a third texture with the eastern and western edges equal to the appropriate portion of each texture, and the middle made thru feathering pasted portions of the real world. That's what I did for the interface between my Bowerman and my Elma areas to enable vfr flight between them. Nobody has mentioned the border, as its very hidden.Bob B

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