I have a strange question. My terrain is being rendered by rendering several layers over top of each other, yet does not disable the z-buffer during this process. When I say over top of each other, I mean 2 triangles have vertices that are in the exact same position. There is no z-fighting at all. Is this because the vertices are basically welded together, in the same exact positions? You can see a picture of the terrain here Is it safe to rely on this working consistently through other hardware? As in both no z-fighting, and also having the layers drawn in the same order? I'm using a Radeon 8500, and have access to no other cards. If I don't need to disable the z-buffer, I've just skipped a horrible situation that I thought I would need to face. Thanks for any suggestions.

I'm not using the exact same buffers. But triangles which overlap are individually exact.

So this is still okay? [smile]

Yep, it's splatting. There are some detail images in here

Thanks for your help

Thanks for clearing that up for me.

edit: Oops, you answered one of my questions while I was asking. Too slow, I guess.

I'm wondering if it would actually optimize any decent amount to disable z-writes. There is an untexured base layer under the textured layers. This base has all triangles that exist in the area. Basically it just averages it's vertex colors based on the 1x1 texture mips applied to each point. It's needed because you can actually see through the layers where they overlap. And I planned on needed it for z-buffer problems. Guess maybe I was wrong about that one. Still, if disabling z-writes helps, it's not as much of a waste.

The only problem I can think of is that I might need to disable and re-enable the z-writing state a whole bunch of times. If a game object (rock or tree) uses the same textures as the landscape, I would like for them to share textures (not SetTexture() twice). But that would mean my terrain needs to be in the same rendering loop as other objects, where textured subsets are sorted.

So there are three methods that come to me..
1) Throw the terrain layers into the main renderer and leave the z-buffer alone.
2) Same as 1, but disable+enable z-write for every layer as it's rendered.
3) Render all terrain in it's own loop. Render all base areas, disable z-write, render all textured layers, enable z-write.

Option three would not be capable of sharing SetTexture states (with things other than terrain), but it wouldn't need to change to it's vertex shader technique or need to upload terrain chunk section data (only 32 bytes) to the shader more than once either.

Sorry, I guess I'm just thinking out-loud. I appreciate any suggestions, though.

Thank you for the compliment. My graphics card is a bit behind in the technology tree, so I wouldn't have a great time playing with pixel shaders.

Maybe eventually.

Be aware that different vertex shaders can produce different outputs (due to some optimizations). Even if you transform your vertices using the same code.
If you're not seeing any problems it's safe to assume that things works ok.
I've been doing this and when I changed some other things that didn't affect the position I started to get z-fighting. I took me quite a while to find out what the problem was, I thought I screwed up my shader code, but when I turned optimizations off it was working again.

Hehe, want to see my terrain shader?

vTerrain is a global structure specific to each area. The coordinates for each vertex are local, though, so I add the area coordinates. I could actually remove that and store absolute coordinates. Not sure if having really huge texture coordinates would be a problem, though.

One plus is that I can have a "default" area and render it everywhere that I didn't edit in the world editor.