Second Life Forums Archive

Bopete Yossarian

The Script Whisperer

Join date: 28 Feb 2004

Posts: 61

05-08-2004 00:03

Ok, this has been driving me nuts, and I need to ask and see if I'm just terribly confused...

In the admittedly few 3D modeling programs I've dealt with, it seems that the X axis was side-to-side, Z was front-to-back, and Y was up-and-down. Here it seems that Y and Z are switched.

So someone tell me please, which is the standard way of referring to the 3 axes?

Siobhan Taylor

Nemesis

Join date: 13 Aug 2003

Posts: 5,476

05-08-2004 00:29

Actually, X is west to east, Y is south to north and Z is down to up.

And to answer your question, this seems to be the standard way. Though I have seen different.

Sio

*edited after I reread the question, lol... aaarg, I need coffee!*

_____________________

http://siobhantaylor.wordpress.com/

Jake Cellardoor

CHM builder

Join date: 27 Mar 2003

Posts: 528

05-08-2004 13:26

I guess it all depends on what you expect to be the default viewing orientation. I expect the x-y plane to be the ground, because I assume that a position's "longitude" and "latitude" would be described as an (x,y) pair of coordinates. In which case z would be altitude. This is indeed how SL treats the global coordinate axes.

Bopete, it seems like you expect the x-y plane to be perpendicular to the ground, where y is altitude. That would imply that "longitude" and "latitude" would be the x and z coordinates.

In a sense, you're looking toward the horizon, while I'm looking toward the ground as if I'm reading at a map.

Bopete Yossarian

The Script Whisperer

Join date: 28 Feb 2004

Posts: 61

05-08-2004 20:10

Ok, I had to do some research to see if I was really crazy - while that is always a possibility with me (hehehe), I did find several sites that supported *some* of my original assumptions, inluding this one at http://webreference.com/3d/glossary/3dcoord.html

<start quote>
In most applications the X dimension is horizontal to the gravitational sense of the scene. It is the horizon. Positive X values increase to the right, negative values to the left. The Y dimension will typically be vertical, positive coordinates increasing upwards, negative coordinates downward. Z will generally be depth, negative coordinates increasing as you move forward into the scene past the origin, positive coordinates increasing as you retreat backwards from the origin.
<end quote>

It then goes on to say this isn't standard, which is what I was confused about, since math and geometry seems to be very precise and consistant. I suppose that the different methods can be attributed to different uses involving 2d coordinates - maps (horizontal), or CRTs (vertical).

Carnildo Greenacre

Flight Engineer

Join date: 15 Nov 2003

Posts: 1,044

05-08-2004 22:00

What 3D coordinates an application uses depends on where the developer is coming from.

If the developer has done mostly computer-aided design work, Z is up. This is because, in 2D CAD, the Y-axis is vertical, while the X-axis is horizontal. Design is done from a top-down perspective, so the Z-axis coming out of the screen is "up".

If the developer has done mostly computer graphics design work, Y is up. On a computer screen, Y is vertical, while X is horizontal. Design is done from a "user's viewpoint" perspective, so the Z-axis coming out of the screen is the user's line of sight, which is horizontal.

_____________________

perl -le '$_ = 1; (1 x $_) !~ /^(11+)\1+$/ && print while $_++;'

Julian Fate

80's Pop Star

Join date: 19 Oct 2003

Posts: 1,020

05-10-2004 13:24

I think the standard cartesian XY axis graph we all know from highschool geometry was meant to represent a flat plane like a tabletop. That would make X and Y horizontal and Z vertical. Unfortunately, when you see the graph on paper it's hard to know if you're looking down at a table or straight ahead at a wall, hence the confusion.

Paradigm Brodsky

Hmmm, How do I set this?

Join date: 28 Apr 2004

Posts: 206

05-10-2004 22:40

I've uses several 3D modeling and animation applicaitons, including some of the biggest names, 3d Studio Max, POV-Ray, Maya, etc and in my experience, this is not the standard way. As was mentioned above, the point of view here is as if you are looking down on a map. I am used to looking into single or two point perspective towards the horizon.

No method is wrong however, as long as there are only 3 dimentions

The way I remember what axix is what is by associating two concepts.

* Mathematics, the points of a graph are always writen in alphabetical order, (X , Y, Z)

* In computer graphics, colors are described in combinations of (Red, Green, Blue) in that order.

In SL, the X axis is colored Red, the Y Axis is Green, and the Z Axis is Blue.

(Red X, Green Y, Blue Z)

Remember that and you will get used to orienting yourself in no time.

Welcome to the Second Life Forums Archive

x, y, z axes

x, y, z axes
Bopete Yossarian The Script Whisperer Join date: 28 Feb 2004 Posts: 61	05-08-2004 00:03 Ok, this has been driving me nuts, and I need to ask and see if I'm just terribly confused... In the admittedly few 3D modeling programs I've dealt with, it seems that the X axis was side-to-side, Z was front-to-back, and Y was up-and-down. Here it seems that Y and Z are switched. So someone tell me please, which is the standard way of referring to the 3 axes?
Siobhan Taylor Nemesis Join date: 13 Aug 2003 Posts: 5,476	05-08-2004 00:29 Actually, X is west to east, Y is south to north and Z is down to up. And to answer your question, this seems to be the standard way. Though I have seen different. Sio edited after I reread the question, lol... aaarg, I need coffee! _____________________ http://siobhantaylor.wordpress.com/
Jake Cellardoor CHM builder Join date: 27 Mar 2003 Posts: 528	05-08-2004 13:26 I guess it all depends on what you expect to be the default viewing orientation. I expect the x-y plane to be the ground, because I assume that a position's "longitude" and "latitude" would be described as an (x,y) pair of coordinates. In which case z would be altitude. This is indeed how SL treats the global coordinate axes. Bopete, it seems like you expect the x-y plane to be perpendicular to the ground, where y is altitude. That would imply that "longitude" and "latitude" would be the x and z coordinates. In a sense, you're looking toward the horizon, while I'm looking toward the ground as if I'm reading at a map.
Bopete Yossarian The Script Whisperer Join date: 28 Feb 2004 Posts: 61	05-08-2004 20:10 Ok, I had to do some research to see if I was really crazy - while that is always a possibility with me (hehehe), I did find several sites that supported some of my original assumptions, inluding this one at http://webreference.com/3d/glossary/3dcoord.html <start quote> In most applications the X dimension is horizontal to the gravitational sense of the scene. It is the horizon. Positive X values increase to the right, negative values to the left. The Y dimension will typically be vertical, positive coordinates increasing upwards, negative coordinates downward. Z will generally be depth, negative coordinates increasing as you move forward into the scene past the origin, positive coordinates increasing as you retreat backwards from the origin. <end quote> It then goes on to say this isn't standard, which is what I was confused about, since math and geometry seems to be very precise and consistant. I suppose that the different methods can be attributed to different uses involving 2d coordinates - maps (horizontal), or CRTs (vertical).
Carnildo Greenacre Flight Engineer Join date: 15 Nov 2003 Posts: 1,044	05-08-2004 22:00 What 3D coordinates an application uses depends on where the developer is coming from. If the developer has done mostly computer-aided design work, Z is up. This is because, in 2D CAD, the Y-axis is vertical, while the X-axis is horizontal. Design is done from a top-down perspective, so the Z-axis coming out of the screen is "up". If the developer has done mostly computer graphics design work, Y is up. On a computer screen, Y is vertical, while X is horizontal. Design is done from a "user's viewpoint" perspective, so the Z-axis coming out of the screen is the user's line of sight, which is horizontal. _____________________ perl -le '$_ = 1; (1 x $_) !~ /^(11+)\1+$/ && print while $_++;'
Julian Fate 80's Pop Star Join date: 19 Oct 2003 Posts: 1,020	05-10-2004 13:24 I think the standard cartesian XY axis graph we all know from highschool geometry was meant to represent a flat plane like a tabletop. That would make X and Y horizontal and Z vertical. Unfortunately, when you see the graph on paper it's hard to know if you're looking down at a table or straight ahead at a wall, hence the confusion.
Paradigm Brodsky Hmmm, How do I set this? Join date: 28 Apr 2004 Posts: 206	05-10-2004 22:40 I've uses several 3D modeling and animation applicaitons, including some of the biggest names, 3d Studio Max, POV-Ray, Maya, etc and in my experience, this is not the standard way. As was mentioned above, the point of view here is as if you are looking down on a map. I am used to looking into single or two point perspective towards the horizon. No method is wrong however, as long as there are only 3 dimentions The way I remember what axix is what is by associating two concepts. * Mathematics, the points of a graph are always writen in alphabetical order, (X , Y, Z) * In computer graphics, colors are described in combinations of (Red, Green, Blue) in that order. In SL, the X axis is colored Red, the Y Axis is Green, and the Z Axis is Blue. (Red X, Green Y, Blue Z) Remember that and you will get used to orienting yourself in no time.