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nPawn

How to get detailed textures on terrain

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such as the terrain texture in World of Warcraft? Are they just using really small terrain patches with large textures? Or have they figured out some way to get it this detailed? [edited by - nPawn on February 1, 2003 6:53:35 PM]

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You almost got the technique in your topic

"Detail Textures" - Google may find a few for you.


Basically:

- The terrain has a very low detail texture containing really just the low detail colour stretched over it - (usually magnified quite a lot) so that makes the change in colour.

- then as a second texture layer/pass a tiled but detailed texture is placed on top. This tends to have view dependent LOD applied to it so that the detail texture is only applied properly to what is clearly visible.


e.g. taking the bottom screenshot and ignoring the sprouting plants, there is likely to be a base map with shades of green and yellow stretched over the whole landscape. On the polygons nearest to the viewer a second map will be modulated on top containing the swirly details - that map can be tiled/repeated many times in the scene, but since the colour map changes lots it looks like every pixel in the image has a unique texture map.

The same technique was used on the grass in Halo

--
Simon O''Connor
Creative Asylum Ltd
www.creative-asylum.com

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Yes but if you tile it like that won't you have that detailed texture across the entire terrain? I guess I don't understand how you'd vary that detail texture at all, if you went from say grassland to rocky mountains? Like in that pumpkin patch screenshot they have detailed garden dirt, but past that a little ways by the barn it looks like they have detailed grass. How to make that detail transition?

[edited by - nPawn on February 2, 2003 1:10:35 AM]

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I’m just a novice myself. I’ve had similar questions before, particularly with Morrowind. In Morrowind, they seem to be using small tiled textures rather than large ones. They cover some small area like 8x8 vertices (I forgot the actual size, but that’s close).

Here’s one screenshot of a piece of ground in the Morrowind editor :



In this next screenshot, I chose a different texture—a texture of a stone road— and I then clicked on the ground to select the texture into that patch of ground:



You can see that some edges are blended with adjacent patches, but the edge on the right side is not blended. (I’m using a GeForce2 Pro, btw).

I’d like to implement the same thing they are doing here. I like the idea of texturing terrain in blended patches like this instead of having to draw a big texture in some image editor. But I’m not totally sure how it’s done. If you want to blend a tile with any adjacent tile, then in the worst case you would need to blend 9 different textures, which the graphics card obviously can’t handle. The fact that there is one edge that did not blend may be a clue that the engine will only blend as many as it can and will not blend any more. That would mean it’s up to the designers to limit the number of different textures adjacent to any given texture. But since you can only use two textures at a time (in a GeForce 2, as far as I know) I’m not sure how this can be done.

I should also add that I don’t know if that unblended edge shown above will actually appear in the game. I haven’t yet tried saving the edit and then running the game, but I should probably do that.

Any idea how Morrowind does this?

[edited by - JimH on February 10, 2003 4:57:43 PM]

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I did see that Bloom article before. But I found his explanation rather hard to follow so I didn’t spend much time with it before. But I just now spent more time to understand it.

I don’t think Morrowind does Bloom’s splatting thing, at least not how he describes it. In Bloom’s method, he can specify a different texture per-quad (or as he calls it, a tile or “element”), a quad being two triangles made up of four vertices. That’s why he needs the extra alpha texture. In Morrowind, it seems you can only specify textures in 4x4 squares.

So I figured that Morrowind was just assigning a texture to a 4x4 or 8x8 area and then partially overlapping (and thus blending) that area with the surrounding areas. No messing with a separate alpha texture like Bloom does.

Another reason why I don’t think Morrowind is splatting is this: I found out that the seam you see in the second picture above is actually in the game as well, not just in the editor. So apparently, the game engine does not do anything like splatting or multiple passes, since if it did I’d expect there wouldn’t be any seams. So I’m guessing they depend on the designers to make sure there are not too many different textures adjacent to each other. It seems that a 4x4 tile with a texture assigned to it can have up to 2 different textures adjacent and still blend ok, in general. But any more than that and you get a seam. However, I have also produced cases where that rule is not followed exactly, so I haven’t been able to deduce just what’s going on.

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Does splatting work ok with an Octree? I''m doing brute force right now but want to go to an Octree soon. This splatting look like it might be a good method for finer detail on terrain but I don''t want to waste my time on it if it doesn''t get along with Octrees?

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Well, regarding Morrowind, after playing around with textures more, I think I figured it out. It does seem only use only two textures at a time. So no multi-pass rendering is needed. It requires that designers arrange the textures correctly. A texture is assigned to a 4x4 tile and it is influenced only by the tiles that are adjacent to it on the west, northwest and north sides. So out of those four tiles, there can be only a total of two different textures.

Sorry to hijack the thread, it just seemed to be a related question.

quote:
Does splatting work ok with an Octree? I''m doing brute force right now but want to go to an Octree soon. This splatting look like it might be a good method for finer detail on terrain but I don''t want to waste my time on it if it doesn''t get along with Octrees?


I don’t see why not. Although I think most people use a quadtree for landscape. In that splatting article, Bloom talks about using chunks that are 32x32 vertices in size. That chunk could be a leaf node in a quadtree. In any landscape scheme that uses some sort of tiles, a tile can be a leaf.

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hm, the effect in the screenshot looks quite familiar.
does morrowind give you a chance to set weights for the textures?

some parts seem to blend ok, but that edge looks like (i assume only two textures and one weight) one patch has weight of 0 (100% first texture), while the other has 1 (100% second texture) along that edge.

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