What's the W coordinate for?

Bigjohn

So I just noticed in the Unwrap window in 3dsmax that you can manually type in values for U, V and W. The first two make obvious sense. The W one though boggles my mind. I can't figure out why is it there. Tried typing in all sorts of numbers, doesn't do shit.

Anyone has any idea? Or is it just there to mess with my mind?

meshiah

this should explain it

http://wiki.cgsociety.org/index.php/3ds_Max_UVW_Mapping

meshiah

W is the equivalent of Z and represents a direction perpendicular to the UV plane of the map.

AlecMoody

UV coordinates are 3d just like xyz and the W is used by some types of parametric materials. You can also switch the UV window to display UW or VW views. Depending on how your model was unwrapped there might be height information that you can see. I find that it can be useful for making difficult selections and for sorting objects that are overlapped.

Bigjohn

So is it actually useful to us in any way?

meshiah

i haven't seen use for it, but like when you stack mirrored uv's i think one is "on top"
not sure on this, but maybe you could move the w space so your mirrored mesh sits behind
instead of moving it to the 1-1 range, just a though, could be wrong on this....simply put the uv editor is still 3d and 3d has 3 coordinance.

AlecMoody

most of the time no

Olli.

its a handy tool if you have lots of overlaying UV islands and want to be able to choose them seperately. Like if i have a single object mapped to many UV sheets, then i can just have each sheet on its own level in the W coordinate and be able to choose them easily.

Also in the future there might be something cool like 3d textures, where you can have 3 dimensional UV coordinates and a sort of material is projected on to the surface.

Ace-Angel

99% of the time, W coordinates have no purpose.

Those other 1% of the time, they have minimum use, such as unwrapping in 3D workspace, and dictating, on a symmetrical object, which side is ontop or inverted for Normal Map backing, and some fancy shader material work.

However, since almost ALL applications allow you access to Mutiple UV channels, you might as well ditch any ideas for the W coordinates and instead make a second Unwrap for your fancy materials.

monster

There are some procedural texture types in 3ds Max that use the W coordinate.

r_fletch_r

monster wrote: »

There are some procedural texture types in 3ds Max that use the W coordinate.

thats all based on object or world space though isn't it? the UV's only apply for viewport previews.

MoP

r_fletch_r: Most map types allow you to choose various Source coordinates - lots of parametric maps default to Object or World space, but you can still pass them the Explicit Map Channel if you want to use UVW coordinates for a 3D parametric map.

In summary: Yes, the W axis of UVW co-ordinates can sometimes be useful, but in general, no, game artists do not make use of it much, if at all.

Macattackk

so the W is like photoshop layers for UVs?

pior

No, it's like Z for XYZ.

Macattackk

yea but isnt that the same thing? If I understand this correctly it seems more like layers cause youre not actually translating anything in 3d space, youre using a "fake" 3d system in a 2d space.

AlecMoody

macattack: switch your uv editor to one of the views other than UV. UVW is just like XYZ but normally you only see it from a top view.

pior

Yeah, what Alec said. Just imagine it as a top view of a 3D model. A UVW vert can have a different W coordinate than than another one it is connected to. So nope, not like layers at all