I've never seen the map zoom in skyrim in action, but from the look I would guess, that they use some kind of LOD for the terrain mesh and texture. So, if you don't have a lod system for your voxel world, you will have a hard time to get it done in realtime. Even worse, if you really zoom out quite far and your cube size is relative small, then you will have fun with subpixel rendering and z-buffer effects.

Therefore I would think about a fix camera high and angle and an orthogonal projection. This way you could render tiles and save them on a texture and update them only from time to time.

I've never seen the map zoom in skyrim in action, but from the look I would guess, that they use some kind of LOD for the terrain mesh and texture.

They do exactly that.

Even before Skyrim, Bethesda had their whole world map rendered into different levels of detail, stored into meshes and textures inside the game files. The LOD system picks up the different levels it needs and loads the models accordingly. So nothing is processed real time in that respect, its just pre-made low poly/low res models/textures loaded as the game needs them.

For Skyrim they just picked up the least detailed level and assembled it into a 3D map. Make terrain LOD, get a sweet and free ingame map. Pretty clever

@riuthamus. I guess that if you want exactly the same on a voxel world, you'd need to generate the map on the fly, depending on what you're doing. If players can change the terrain, then it should be updated every time the player open ups the map. If it doesn't, you might get away with just generating it once on a "building world/loading game" screen before the game starts.

Or you could just set up intervals at a fixed time in which the map updates and just let the players wait for their stuff to appear on the map. Normal players aren't that picky with the technical details if the game keeps them entertained nevertheless.

As far as for the implementation, no idea, i'm not that experienced yet. All I know is what caldiar said, octrees could get you easily different interpretations of your world in different resolutions (more exactly, different cube sizes). By zooming in, you go into lower levels of the tree, by zooming out you go into upper levels. Though if you don't already have your map stored in a octree, changing the whole world representation may not worth the hassle.

I *think* that it may be too hard for the CPU to do all of that (massive traversing of octrees if the map is big enough), but I'm not sure, as I said, I don't have any relevant experience.

Aren't these 2 different problems? Apples and oranges?

Skyrim has a fixed map.

The map screen doesn't actually zoom out. The menu screen where you select the MAP option scrolls out of view while the map fades in, giving it the feel of zooming out. It's just a very low polygon version of the terrain, with a basic diffuse, normal, and spec map on it. Both of them either kept in ram, or are small enough to load in half a second. Every location you've discovered then gets an overlay icon on the HUD.

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Off the top of my head (knowing nothing of your program's architecture), for a changing voxel world, I'd have a low detail overworld map that was made up of tiled models. Each model would be a low detail version (8 to 1, 16 to 1, 32 to 1, whatever) of everything in it's zone. When enough changes are made to a zone, I would update it's associated overworld tile. (no need to update after every change, because at that small resolution (8/16/32 to 1) you wouldn't see the changes anyways!

Since you only want to render the top tiles, I would probably start with a small grid model for every overworld tile, then have a diffuse and heightmap texture that get updated. Then you just render out your same grid model for every zone, with a unique texture set for each. You can try different resolutions of grid model to see what gives you the best results.

For the texture generation, I'd just do a for loop over all the top most tiles in the zone, and get their average color and height then RTT those values right into the texture.

I think this would give you an overworld map that was a good rough approximation of your game world.

Disclaimer: I pulled this right out of my ass based on the first post.