Information on terrain LOD

[typdef]

Hi !

I would like to make a google earth lite software. Can I easly and quickly represent a spheric planet earth with several LOD everywhere on the planet, with TV3D LOD system and based on nasa HGT tiles for ground vertex and custom tiles set for textures ?
If someone have some tutorial or exemple/documentation going in this direction, I would love it.

Thank you for your time,

[Lenn]

I tried doing something similar a while ago. The tv3d terrains are not very suitable for represneting a spherical planet, they work on the XZ plane and if you try to artificially curve or rotate them based on longtitude/latitude you may loose resolution due to effective vertice occupation in terms of a units squared area (XZ). It's better to use a custom mesh format, but that depend on how many LOD stages you need and what the min/max levels are. I used TV3D terrains for high res view, when down on the planet, and custom mesh when zooming out and going into space. It was pretty seamless but it took me around a year to do it. In the end the high-res maps were taking up 100s of GB os hard disk space, so it wasn't a good offline solution. You'd have to think about creating a map cache, how that's handled, etc etc.

[Lenn]

If someone have some tutorial or exemple/documentation going in this direction, I would love it.

Oh and, no, there are no tutorials on how to create Google Earth. You simply need a great amount of general knowledge working with 3D engines. Good luck!

[typdef]

Thank you for your answer,

Well, I basically did all what you described in raw opengl and I have something working very well, with custom data format for tiles (also several GB on hardrive) etc, but I was looking for a SDK/graphic-engine because every time my project evolve I have to add features to my pseudo 3D engine, and I don't want to reinvent the wheel.

However it seems hard to find an engine that correspond to my needs, there is a lot of open/free of charge 3D engine with their SDk outthere, but they all seems to target plane based terrains as you said for tv3d.

If someone know a tool/sdk/engine that could correspond to my use it would be great,
Thank you for your time,

[Mithrandir]

Ogre3D allows you to define your own scene nodes. They have some examples for the "typical" terrains but you have full control of how the scene is being drawn/stored.

[Lenn]

I doubt you'll find any engine that has terrains that aren't on a XZ plane. Your best bet is to convert your opengl code into a mesh format used by the engine of your choice, it will probably work with a bit of modification.

[jake3hoover]

These are the basic steps which should be followed:
Fixing Mesh Errors
Creating the LOD Meshes
Creating the LOD Diffuse Maps (Color Textures)
The Naming Bug
The Black Texture Bug
Update LOD Information
Testing
Additional Notes
Portability