Mat Churchill wrote:
I am going to have a second shot at photo scenery and have been looking at the last way I did it. I have asked this question before, but wonder if there is anyone out there who knows where I can find out how terrain texture tiles are placed in FG.
It looks as if they are placed by FG and not during scenery building by TG. I say this as when I open up scenery tiles in FGSD there is definitely no existing series of squares. Yet the terrain textures are laid over the scenery in a fixed grid that doesn't change however I build the scenery. Here is a screenshot of the "grid" (made by using all black terrain texture tiles with a single pixel white edge)
http://www.projects.34sp.com/Flightgear/tn/a-Black-grid.jpg.html
Yet TG does define what terrain texture goes where. So there you go I'm
confused.
Oh boy, I'm not sure I can fully explain the scheme, but I'll summarize. I wanted a way lay the textures down in a pre-determined fixed grid, but I also wanted a way to "size" the textures in the materials.xml file. In other words, one particular texture might be sized correctly if it covers a 500x500 meter area while a different texture might be sized correctly if it covers a 2000x2000 meter area. You can specify the coverage area in the materials.xml file which essentially means you can resize the coverage area at run time.
Terragear calculates texture coordinates based on a 1000x1000 meter coverage area (I think.) But it does it in such a way that the coverage area can be scaled at run time without running into strange artifacts.
So you are right, it's a bit confusing, in the end the scheme has some nice properties because you don't have to know in advance what area of coverage a particular terrain texture is scaled for.
Basically last time I spent ages copying this grid by hand, then building it into the scenery using TG. A fuller understanding of how those terrain textures are placed is going to hopefully enable me to come up with an at least partially automated way of placing photo scenery tiles.
Is there a LOD system for terrain textures ?
Currently there is no LOD system for terrain textures, neither is there any texture paging scheme implimented.
Curt.
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Curtis Olson http://www.flightgear.org/~curt HumanFIRST Program http://www.humanfirst.umn.edu/
FlightGear Project http://www.flightgear.org
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