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Comment by tezza | Hacker News Reader

Does this use the same coordinate space[1] as Maya , or does it use the same coordinate space as Blender ?

Blender has no end of hidden trouble importing to Unity because Unity chose to be the same as Maya

[1] https://blender.stackexchange.com/questions/471/is-it-possib...

Dust3D use right-handed coordinate space, X - front view, Z - side view, Y - up. I am not quite sure what exactly coordinate space other software use, but I make sure the exported fbx looks as the same in Unity, and the exported glb looks as the same in Godot.

If the fbx loads into Unity fine, are you not using a left handed system, or are you flipping it on export?

edit - I'm an idiot, Unity does its own conversion to left handed on import.

OT: First time ever seeing a post of mine `randomly` linked here on HN. :)

TIL.

The fact that gaming and Maya use one (Y-up) and that CAD and Blender use another (Z-up) brings the classic xkcd to mind.

https://xkcd.com/927/

The fact that there are only 2 makes me think that it doesn't apply though. I just hope nobody trise to go make a third.

There are also left-handed and right-handed coordinate systems...

This is correct. Most CG and 3d software (Max, Maya, Blender, CAD) uses a right handed coordinate system, which matches the convention in physics, however they vary in their choice of Y up or Z up. Video games almost always use a left-handed coordinate system with Y up. This is because DirectX and OpenGL chose to represent pixels on-screen with (X,Y) coordinates with the Z coordinate increasing as rays extend from the eye outward.

Wow, I had no idea it was so varied

To add to the confusion, while in both OpenGL and DirectX treat Z axis as depth, DirectX uses a left-handed coordinate system, while OpenGL uses mostly[0] right-handed one.

[0] - https://stackoverflow.com/questions/4124041/is-opengl-coordi...

OpenGL-the-interface is kinda neither (screenspace aside), since the application supplies/does all transformations (glFrustum and friends are long deprecated).

There are more than two, Unreal has a coordinate system so special that Tim Sweeney apologized for it.

https://mobile.twitter.com/timsweeneyepic/status/95266147450...

Most CGI software where in-house software before being commercial. So the "what others do?" question never popped. :)

I think that XKCD only really applies in systems where there is an infinite number of possible ways to do something. While there are a lot of ways you can configure a coordinate system the number of reasonable / non-intentionally obtuse ways is finite.

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