What's an 8-sided tiled texture ?

Acumen

Hey, I stumbled over this forum post and to be honest have never heard of an 8-sided tiled texture. The tutorial itself is quite hard to read through and understand, but this guy mentions an article in a Unity Magazine (that looks quite good, qualitywise) so I wonder whether I just don't understand the superior and unique innovation that is described.
To me it just looks like he tiles the texture in itself.

So the questions are:

1) What is an 8-sided texture ?

2) What benefit does it come with ?

3) How can a texture be more than 4-sided tileable, when a texture doesn't have more than 4 sides O_o

Unfortunately, he only attached it in the forum post and I'm not sure whether it's fine to upload it on my own webspace.

Here's the magazine:
http://www.3dattack.us/3DAttack/July-August2010.html

edit: alright, I think I understood what it does, but I don't get the use o if in a game. Why would I use a texture like that ?

Brice Vandemoortele

I'm just making a guess here, I might be completely wrong

Tiling textures usually wrap using the hardware sampling method. Whatever the geometry is, once you reach a side of the texture it just repeats the pixels from the other side. This is the regular approach and there's plenty of method to create them, the more obvious being the offset function + stamp in Photoshop.
You could say that in some way the tile 'in translate', or 'on 4 sides'

I've created tiling texture sets in the past that were applied to each faces of a mesh, where each quad had 'unitized' UVs. Each corner of the quad's UVs are either on (0,1), (0,0), (1,1) or (0,0) and the whole image is displayed on every single quad. The problem is that the UVs can be rotated around. So the textures need to tile BOTH in translation AND rotation.

Think it this way: 'Translation' tiles have 2 unique sides: the top and bottom ones are identical, and left and right as well. 'Rotation' tiles only have half of a side that is unique. Since they can rotate, a side may tile with itself, so the right side of its side (still there? :P) must match the left, hence be identical. (I know, a picture would help...)

Long story short: they're a pain in the ass to author

Acumen

I think that's pretty much what is described in the tutorial. Just not as well spoken ^^

So I understand the concept of it, which is a relief.
But still I'm asking myself, in what situation would someone use this in a game ? On what kind of Assets/Environments does this come in handy and is better than a boring normal tiled texture ?

Brice Vandemoortele

I had to use it in a PS2 engine, which was of course fixed pipeline. Ideal texture size on ps2 is 128*128 4bits (16 colors) and the engine used a subdivision terrain system. Everything was modeled in quads and subdivided on the fly (with nifty low res displacement maps, which was very nice at the time). I guess this is all obsolete with modern shader capabilities, but i would still make sense on some handheld devices.

Acumen

Ah thank you so much for clariying. Found it quite surprising to read of something like this, when I'm stunned by all the shader magic displayed on polycount.
But the handheld sentence made it pop for me. Totally forgot about these
Thanks again !

Eric Chadwick

We used this technique for terrain textures on the Wii.

To automate most of the process I made an Action in Photoshop, using the free Pizza Slice Mirror filter. Basically I made a new merged layer, ran the filter on it, then added a Layer Mask that masked out everything in the middle, so just the edges of the pizza-layer showed. I added a bit of the Clouds filter to randomize the edge a bit too.

Then it was simply a matter of hand-editing the mask a bit to make it work better with the pattern of each particular texture.

The trick I found was to make that mirrored edge as thin as possible, to hide the butterfly-mirror effect as much as possible, but still use enough to make it tile without seams.

The point of mirroring/tiling half of one side all the way around the texture is so you can not only rotate the texture on each quad, but you can also mirror it, so you get the most variation possible.

Hope that makes sense.