why why why

I found this handy reference a while ago. But yeah, we are kinda screwed.

So just about the only thing everyone agrees on is x is not up 🥲
- YET
- Good news, X is now down.
At least they haven't invented X up (yet)
- You'll never believe my startup idea
There's only one quadrant of this that should be acceptable to anyone! Positive X, positive Y!
- Nope, the bottom right quadrant is the acceptable one. Z is up and follows the right-hand rule. I will die on this hill.

I work in 3D metrology and the consensus is right handed and Z up. Had no idea left handed existed!

How does projection work in your field? X, Y, Z get converted to X, Z and 2D screen planars have no Y axis?

Who invented this, why did she do it and where to send my official letter of complaint?
- I thought right-hand rule with Z up as thumb was standard in science? You usually project on the xy-plane, for example when calculating the distance to objects on a flat surface.
- TBH I'm not sure I totally understand the question but projection is very useful to decompose the orientation of elements, like a cylinder that you just measured with a machine or a scanner. The coordinates and orientation (angles) can be projected in the three main planes XY, YZ and ZX.
This can happen if you accidentally pilot your player character into a singular linear transformation.

Ugh, when I have to open CAD for a project at work I have to setup a new coordinate system with Z going up, every time. The engineers just work with Y up for some reason. Too lazy to change it perhaps? Solid works and Inventor default Y up? I'll never understand it. I definitely understand this meme. There's also models with an origin 10 feet off in X and 20 feet out in Y. I just do not friggin get it man.

Because math works with Y up. Physics steal from math, engeneering steals from physics, so, here you are.

What I can't get is imperial measurement system. Apparently, nobody but americans can. And that stuff is far worse than Y and Z switching places.
- as a minecraft player learning how to use autocad, i thought y up was alot more ubiquitous then it apparently is
- That's what I don't get. Why would they make Z up when in algebra, Y is up. It's all based on math, shouldn't we keep consistent on that?
- What I can't get is imperial measurement system. Apparently, nobody but americans can
  
  I'm not American but I've been living in the USA for ten years and I still have trouble with imperial measurements. It's painful dealing with fractions of an inch instead of millimeters.
- That's not true though. While there isn't a standard, convention is to have z up in mathematics, as z is extending the xy plane we normally work with into a third space.
CAD used to be digital abstraction of the physical media that is 2D drawings on paper, so XY is the plane of the paper going horizontal/vertical, and most detailing are in vertical cross sections so Y ended up being up most of the time.

The Z axis is then Frankensteined into the existing system to get a proper 3D representation, so it became the depth axis for the existing XY plane.

In Minecraft it's even more evident as Notch Frankensteined the Z axis into a game engine that's originally developed for side scrolling.
In which world should Z point up and Y represent depth?

Totally crazy opposite world, where cats hunt dogs and rain goes up? This is plain evil...! :-)

Nobody commenting on the chirality difference…

It gets more cursed the more you look at it:

you have to convert the coordinate axes (swap z,x,y)
then you find out the right/left handed is flipped
now your brain melts if you even try think how to solve this with transformation/rotation, what ever.

It’s called the theory of Gravity after all

In robotics I use right hand coordinates with z up. So a car is moving in the 2d xy plane and z is the optional third component. This makes sense to me. For some kind of painting on the screen I can understand why you use y as up. Then again, I know these as uv-coordinates.