I found this handy reference a while ago. But yeah, we are kinda screwed.
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.
you’ll get bitten during projection when depth is converted to 2D screen coordinates, which is X and Y. Better do it right from the start.
At least they haven’t invented X up (yet)
You’ll never believe my startup idea
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.
I only know thumb = motion/current but now since you say, it’s clear: people used x/y for 2D logically but the 2D plane used to be paper. which is parallel to the earth surface (usually). Computer screens are perpendicular so Y points up, not away from you.
So this makes sense with paper, TIL. With computers, Z traditionally means depth.
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.
Sorry for being unclear, I was talking about screen projection. For actual rasterization.
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.
Nobody commenting on the chirality difference…
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?
Because the z axis is represented as an extension of the xy-plane, coming out of the paper essentially, so we represent it as up
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.
Might depend on where you were learning.
On paper, when I was learning Descartes’ coordibate system, we used Y as up and X as left-right. And when it was time to plot in 3D, we used Z to “extend” the plane into yourself and away from yourself.
You just hold your sheet of paper perpendicular to the ground (or just use a whiteboard) and it all makes sense.
