I'm an OpenGL developer, currently developing a small terrain model renderer. I'm sending this message to this list, because I think that developers of FlightGera hav come up with similar subjects and can provide me with a working solution.
What I want to achieve is to render multiple terrain grids of different resolution that contain common areas without the rendered models to "mix" because of the different resolutions used. That is similar to "cutting rectangular holes" to terrain models, without of course preprocessing, splitting, or braking the initial terrain grids into pieces. Let's say I have three rectangular heightfield grids, the one covering the entire North Anerica terrain, with a resolution of 1 km, a grid covering the USA area with a resolution of 500m and a grid covering the area of Nevada state with a resolution of 100m. I want to be able to render those grids together at the same scene, but because of the different resolutions, the heightfields mix in many cases.
So the ideal thing (and what I want to achive), is that when rendering those grids, I want to be able somehow to punch a vertical rectangular hole in the correct position and with the size of the USA grid in the North America grid, place the USA grid there, and then put a verical hole in the Nevada area in the USA grid, and place the Nevada grid. Grids are not "aligned", so that can't be done by preprocessing grids and cutting the right holes in them.
So I am asking for a way, or technique so as when rendering an object after another, to avoid rendering the part of the object that is vertically (same x,z coords) "covered" by the previous object, so as to avoid mixing them. Here (http://students.ceid.upatras.gr/~mantesat/render.jpg) is a quick note about the clipping I want to achieve. It is a side view of a rendering of a terrain model, consisting of three datasets. How does FlightGear face similar problems?
Thanks in advance
Athanasios Mantes
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