Hi Licu, On 3/8/07, LiCU A <[EMAIL PROTECTED]> wrote:
Hello, I'm writing an export plug-in for a terrain modeling application. I've been browsing the OSG documentation and examples in the last days but I still have some uncertainties. First of, what's the best way to construct the terrain scene graph? For now I've been using osg::Geometry and Drawables to create generic geometry surfaces to represent the terrain zones. I've saw that there is also a osgTerrain but is this only for terrain generation or can it be used to keep and render the terrain data, too? To be noted that the terrain is made of multiple zones with multiple layers of textures and also LOD must be implemented (and maybe some paging mechanism).
We have made something similar to your development, and now we have a QuadTree based subdivision, and the Elevation Tiles are created in a plugin as you. Currently we support layers using multitexture but we have lots of problems with this method. Our intentions are to change layers or deactivate layers, or elevation or whatever needed by a GIS, while running and viewing our terrain (earth). If you are planning to render one fixed set of layers, then I recommend a multitexture approach, because is more efficient and easy to manage it. If not, we are now thinking to develop a multipass approach because the big number of possibilities with changes in layers doesn't give us good visuals with terrain creation. (For example, If you don't have elevations and you make a big zoom to an area, then you add elevations and tiles grow one by one, creating holes meanwhile one has elevations and the neighbour not). ossimPlanet is a project that uses first approach, but I think they don't make changes in layers when running. And another question, if I am to represent the terrain
thru normal geometry how do I encode multiple layers of textures (using multi-textures and multi-pass if necessary)? How can I use the same osg::Geometry but with different render states and textures?
About the geometry creation, inside osgTerrain, there is a piece of code that make the stuff, using an ellipsoid model (if the database is geocentric). We used that code to begin our geometry generation. osgTerrain is an impressive work you can extract some good ideas from there, and also from ossimPlanet. Greetz, Rafa.
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