Top one is incorrect. Z needs to point outwards.

The top one is wrong because it violates the right hand rule.

I legit had no idea anybody actually used the upper system until now. I had to read the comments just to see whether the upper system was just some sort of joke. I am horrified.

One of my friends and I used to always have this debate because of our different backgrounds. I got used to +Y being up because of doing physics for several years and seeing side-on diagrams that needed to account for gravity. My friend has a background in geology, so he's used to top-down surveying maps where +Z is up. It all depends on your perspective.

But my way is right. We need to have standards, people.

Z is elevation. Any real world application, z goes up down. 3D applications SHOULD use it for elevation. I despise that many do not. It's so fucking confusing. 2D, sure y go brrr. But once that 3rd dimension is added, y needs to take several seats and quit trying to take on dimensions it doesn't have any right to.

No, there are 3 actually:

Thanks to 3D printing Z is firmly “up” in my brain even if the modeler I use does it differently.

Yeah... As a Blender 3D artist, Z axis has been baked into my brain as the up/down axis.

In my brain Z is Up, Z is Height. In my job I have to deal with both all the time which is quite annoying.

In 2D Y is up, in 3D Z is up.
X is always red🤷‍♂️

Z is always depth. Both are correct but define different perspectives. Top is looking across the landscape from an arbitrary floating perspective, bottom is looking down with anchored mapping to the surface.

In a 2D game Y is up. Going from 2D to 3D would make sense to add another dimension forward to account for depth.

However if you start with a map of a 3D surface then North is Y and East is X you'd add Z to account for elevation like everybody making maps would.

I guess it depends on how you look at it.

y-up ftw

It's easier when writing 3d renderers cause the x and y coordinates of the 3d points eventually become the x and y coordinates of the 2d points on screen and it's easier to keep track of

X is up, there now no one is happy.

Don't forget the handedness of each coordinate system!

The second fellow is a machinist, like me.

I'll leave this here for context (bottom right is the only sane one)

Minecraft

Z is depth, full stop, and I have my fists raised, Queensbury-style, to anyone who contends otherwise.

My son and I have had this very argument. I think the top one is right as he thinks it's the bottom one. I have a coding background and he has a 3D printing background. I figure that's why we're different but I know nothing about 3D printing beyond the cool stuff I see on the Internet and things he's printed for me.

<i,j,k> vector master race.

There are clearly more than two. In the top image that z-axis is pointing in the wrong direction.

Unless you're into magnetic resonance and use rotating frames:

Above and below the page/plane is the z-axis.

But some people "hold" the page up in front of them, or down on the table.

Neither of these are right. X is forward, Y is to the right and Z is down.

Source: https://iansguides.com/tutorials/aircraft-coordinate-system-and-anatomy/

I'm the bottom person. X and Y need to be on the same plane.

I hate this so much in the 3d printing world. I want it to graph from the angle I'm watching it, not from the angle the nozzle is.

I've never heard of Y pointing up. Z is always up. Unless you're talking about lathes, where Z points to the right and X points up. Whoever came up with that, I hope his frying in hell.

Weird didn't everyone learn XY on paper on a desk first? All they did was add z axis to that original concept for elevation which gives us the bottom image.

Top image is like if I held paper straight parallel to my face.

I am the latter, because if I draw a X-Y plane and lay it on the ground, it aligns with that XYZ reference frame.