OpenGL terrain

Are you asking how to store pathing data in a texture? If so, think of the terrain as a grid and each cell of the grid is a pixel of the image. You can then store bools for whether you can go each direction from a given cell (pixel). That's usually not even necessary since there are usually rules (can't climb X elevation change as an example). It is useful in some limited situations though.

Unless you're using path data in a shader, there is very little reason to use a texture though. You'd often duplicate the data anyways since you still need to write code that can path with better knowledge than just neighboring cells unless you don't have AI players and don't allow the user to move to distant points with a single action.

If that's not the answer you're looking for, you might try posting in a more general forum than OpenGL. It sounds like you're asking about pathing, terrain, etc. in general, not anything specific to OpenGL.

If you are asking what i think you are asking I also use texture arrays but I store selection info in the vertex RGBA components. (up to) 2 textures and a transparency for belding (if req)

Automatic selection of textures for grass, rocks, cliff-sides, etc. is one part, but paths need to be manually drawn through the terrain via some kind of editor. Your terrain system needs to support not only automatic texture selection based on height and slope, but also manual texture applications for artists.

L. Spiro

Depends what you mean by "path" is this just where you can walk on the terrain? OR do you mean painting dirt trails and such?

Typically for AI paths, you take the height map and create an array of walkable squares. Each square is walkable if the normal of it is pointing up towards the sky. For instance a 45 degree slope might be your cap:

if (dot_product(Tile.normal, Vec3(0,1,0) < .5) { // terrain tile is tagged as walkable;}

You could have a look at texture splatting.

If you use all four channels of a splat/detail texture you can have four types in a single base texture, resulting in four possible textures. I'm using two splat textures so i can have up to eight different textures applied to the terrain. This is more than enough for a single terrain patch.