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Houkah
03-04-2004, 07:47 PM
I was wondering what the U and V in UV coordinates stands for? I need to write a paper for work for non 3d folks and would like to be as thorough as possible in my definitions. Thanks in advance.

gmask
03-04-2004, 08:05 PM
V is for vertical and U is for Horizonatal.. don't know why though..


http://www.halcyon.com/asllc/uv_coord.html

Another clue is from the book Visual Effects in a Digital World book.

It defines U as refering to the first curve or U Curve and the U direction.. essentially these kind of abbreviations are arbitrary because in 3d space how do you know which direction is up? On a surface that can go any number of directions, horizontal and vertical are only valid if you have "unwrapped" the patch and laid it out with that orientation to the origin of the surface.

Likewise X,Y and Z are arbitrary letters assigned to the dimision of 3d space. There are inconsistancies with these where in terms of CAD, milling and architecture programs the Z axis is vertical or Z up but in cinematography Z usually refers to away from the camera and Y is up instead of Z.

Houkah
03-04-2004, 09:01 PM
Thanks for the reply and link Gmask. Yeah i was always curious why Z was veritical in CAD and (i think by default) in 3dsMax <-- don't quote me on that tho i haven't used max in a long time.

gmask
03-04-2004, 09:19 PM
Originally posted by Houkah
Thanks for the reply and link Gmask. Yeah i was always curious why Z was veritical in CAD and (i think by default) in 3dsMax <-- don't quote me on that tho i haven't used max in a long time.

Yeah and I beleive that is the case with MAX because it originated from more of a CAD and Architectural background where you woul dbe looking at floor plans from over head.. so the away from camera is actually a vertical axis.

I imagine that since Alias softwares came from more of a automotive design background that you are mainly looking at a profiles so therefore the Y is a vertical axis. Since Maya is more geared towards entertainment that z is therefore away from the camera looking towards the horizon.

I'm speculating a bit on this but I think there is some evidence that these ideas are more or less correct. In any case the letter assignments of arbitrary.

Larrikin
03-11-2004, 06:35 PM
I read once that the letters U and V were chosen because they preceed XYZ in the alphabet.

EricChadwick
03-14-2004, 02:42 AM
Don't forget about W...

U is generally for the width of the texture, V for the height, and W is used for depth when you are using a 3D texture, like a procedural or a layered set of 2D bitmaps.

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