19
why why why
(lemmy.world)
I found this handy reference a while ago. But yeah, we are kinda screwed.
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.
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.
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.
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.
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 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.
this post was submitted on 06 Jul 2023
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